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ObjectivesWe used linked individual-level data from national registries to compare the risk of severe outcomes among unvaccinated COVID-19 cases MethodsOur outcomes were hospitalisation with acute COVID-19 or multisystem inflammatory syndrome in children (MIS-C). We calculated adjusted risk ratios (aRR) with 95% confidence intervals (CIs) using multivariable log-binomial regression, adjusting for variant wave, demographic characteristics and underlying comorbidities.ResultsWe included 10,538 Alpha (21 hospitalised with acute COVID-19, 7 MIS-C), 42,362 Delta (28 acute COVID-19, 14 MIS-C) and 82,907 Omicron wave cases (48 acute COVID-19, 7 MIS-C). The risk of hospitalisation with acute COVID-19 in cases ConclusionsWe found no evidence of a difference in the risk of hospitalisation due to acute COVID-19 among unvaccinated cases Article SummaryWe compare the risk of severe outcomes in unvaccinated COVID-19 cases What’s Known on This SubjectCurrently, limited evidence suggests no clear difference in the risk of severe disease outcomes among children infected with different SARS-CoV-2 variants. The risk of multisystem inflammatory syndrome in children following infection with the Omicron variant has not been quantified.What This Study AddsWe find a lower risk of hospitalisation due to acute COVID-19 among cases

BackgroundCOVID-19 vaccination was recommended for adolescents in Norway since August 2021. In this population-based cohort study, we estimated the BNT162b2 vaccine effectiveness against any PCR-confirmed (symptomatic or not) SARS-CoV-2 infections caused by the Delta and Omicron variant among adolescents (12-17-years-old) in Norway from August 2021 to January 2022.MethodsUsing Cox proportional hazard models, we estimated the BNT162b2 vaccine effectiveness against any Delta and Omicron infections. Vaccine status was included as a time-varying covariate and models were adjusted for age, sex, comorbidities, county of residence, country of birth, and living conditions. Data were obtained from the National Preparedness registry for COVID-19, which contains individual-level data from national health and administrative registries.FindingsVaccine effectiveness against Delta infection peaked at 68% (95%CI: 64–71%) and 62% (95%CI: 57– 66%) in days 21-48 after the first dose among 12–15-year-olds and 16–17-year-olds respectively. Among 16–17-year-olds that received two doses, vaccine effectiveness peaked at 93% (95%CI: 90–95%) in days 35-62 and declined to 84% (95%CI: 76–89%) in 63 days or more after the second dose. For both age-groups, we found no protection against Omicron infection after receiving one dose. Among 16–17-year-olds, vaccine effectiveness against Omicron infection peaked at 53% (95%CI: 43–62%) in 7-34 days after the second dose and decreased to 23% (95%CI: 3–40%) in 63 days or more after vaccination. Vaccine effectiveness decreased with time since vaccination for both variants, but waning was observed to occur faster for Omicron.InterpretationOur results suggest reduced protection from BNT162b2 vaccination against any SARS-CoV-2 infection caused by the Omicron variant compared to the Delta. In addition, waning immunity was observed to occur faster for Omicron. The impact of vaccination among adolescents on reducing infection and thus transmission is limited during omicron dominance.FundingNo funding was received.Research in contextEvidence before this studyBNT162b2 (Comirnaty, Pfizer-BioNTech) and mRNA-1273 (Spikevax, Moderna) vaccines have been approved for use in adolescents, based on results from randomized placebo-controlled trials demonstrating comparable immunogenicity and safety profile as in young adults. In addition, observational studies from Israel, the USA and England have reported high protection of BNT162b2 vaccines against SARS-CoV-2 Delta infection among adolescents. These studies also reported decrease in effectiveness with time since last vaccine dose. Evidence on the effect of an extended interval between doses, longer time since vaccination and the effect against different variants is limited. When we first planned this study in early February 2022, no data were available regarding vaccine effectiveness against SARS-CoV-2 Omicron infection among adolescents. To our knowledge when we completed this study and before submitting this article, only one study from England reported results in a preprint on vaccine effectiveness against symptomatic SARS-CoV-2 Omicron infection among adolescents. We searched for studies that evaluated vaccine efficacy or effectiveness after vaccination of adolescents during 2021-2022 in PubMed, medRxiv, bioRxiv, SSRN. We searched for studies with several variations of the primary key search terms “COVID-19”, “SARS-CoV-2”, and “vaccine” (including names of specific vaccines, as BNT162b2), “vaccine effectiveness”, “adolescents”, “children”.Added value of this studyThe rapid increase in the incidence of SARS-CoV-2 infection caused by the Omicron variant in highly vaccinated populations has raised concerns about the effectiveness of current vaccines in adults but also adolescents. In this population-based cohort study, we showed that the vaccine effectiveness against Omicron is lower than against Delta infections among adolescents, including symptomatic and asymptomatic infections. We should note that evidence suggests higher rates of asymptomatic carriage for Omicron than other variants of concern. Vaccine effectiveness that includes asymptomatic cases, as in the study from England, is expected to be lower than when including symptomatic cases only. We found that one and two doses of BNT162b2 among adolescents protected well against Delta. Vaccination provided high protection against Delta infections (>91%) among Norwegian 16-17-year-olds 7-62 days after the second dose. We found no protection against Omicron SARS-CoV-2 infection after one vaccine dose, and moderate effectiveness after two doses (peaked at 53%) among the 16-17-year-olds. Moreover, waning immunity was observed to occur faster for Omicron.Implications of all the available evidenceBased on the available evidence, the vaccine effectiveness among adolescents is similar to that reported among adults, also with an extended period of 8-12 weeks between doses which was used in Norway. Protection is significantly lower against Omicron than Delta infections and immunity wanes faster against Omicron. The impact of vaccination among adolescents on reducing infection and thus transmission is limited during omicron dominance. Policies should take into account the impact of vaccination campaigns among adolescents and their primary objective. Vaccine effectiveness should be re-evaluated when other variants appear as they might have different outcomes as shown between Delta and Omicron infections.

OBJECTIVES There is limited evidence on whether the relative severity of coronavirus disease 2019 (COVID-19) in children and adolescents differs for different severe acute respiratory syndrome coronavirus 2 variants. We compare the risk of hospitalization to acute COVID-19 or multisystem inflammatory syndrome in children (MIS-C) among unvaccinated persons METHODS We used linked individual-level data from national registries to calculate adjusted risk ratios (aRR) with 95% confidence interval (CI) using multivariable log-binomial regression. We adjusted for variant wave, demographic characteristics, and underlying comorbidities. RESULTS We included 10 538 Alpha (21 hospitalized with acute COVID-19, 7 MIS-C), 42 362 Delta (28 acute COVID-19, 14 MIS-C), and 82 907 Omicron wave cases (48 acute COVID-19, 7 MIS-C). The risk of hospitalization with acute COVID-19 was lower in the Delta (aRR: 0.53, 95% CI: 0.30–0.93) and Omicron wave (aRR: 0.40, 95% CI: 0.24–0.68), compared to the Alpha wave. We found no difference in this risk for Omicron compared to Delta. The risk of MIS-C was lower for Omicron, compared to Alpha (aRR: 0.09, 95% CI: 0.03–0.27) and Delta (aRR: 0.26, 95% CI: 0.10–0.63). CONCLUSIONS We do not find clear evidence that different variants have influenced the risk of hospitalization with acute COVID-19 among unvaccinated children and adolescents in Norway. The lower risk of this outcome with Omicron and Delta may reflect changes in other factors over time, such as the testing strategy, maternal vaccination and/or hospitalization criteria. The emergence of Omicron has reduced the risk of MIS-C.

ObjectivesTo explore whether and for how long use of healthcare services is increased among children and adolescents after covid-19.DesignBefore and after register based study.SettingGeneral population of Norway.ParticipantsNorwegians aged 1-19 years (n=706 885) who were tested for SARS-CoV-2 from 1 August 2020 to 1 February 2021 (n=10 279 positive, n=275 859 negative) or not tested (n=420 747) and were not admitted to hospital, by age groups 1-5, 6-15, and 16-19 years.Main outcome measuresMonthly percentages of all cause and cause specific healthcare use in primary care (general practitioner, emergency ward) and specialist care (outpatient, inpatient) from six months before to about six months after the week of being tested for SARS-CoV-2, using a difference-in-differences approach.ResultsA substantial short term relative increase in primary care use was observed for participants during the first month after a positive SARS-CoV-2 test result compared with those who tested negative (age 1-5 years: 339%, 95% confidence interval 308% to 369%; 6-15 years: 471%, 450% to 491%; 16-19 years: 401%, 380% to 422%). Use of primary care for the younger age groups was still increased at two months (1-5 years: 22%, 4% to 40%; 6-15 years: 14%, 2% to 26%) and three months (1-5 years: 26%, 7% to 46%, 6-15 years: 15%, 3% to 28%), but not for the oldest group (16-19 years: 11%, −2% to 24% and 6%, −7% to 19%, respectively). Children aged 1-5 years who tested positive also showed a minor long term (≤6 months) relative increase in primary care use (13%, −0% to 26%) that was not observed for the older age groups, compared with same aged children who tested negative. Results were similar yet the age differences less pronounced compared with untested controls. For all age groups, the increase in primary care visits was due to respiratory and general or unspecified conditions. No increased use of specialist care was observed.ConclusionCovid-19 among children and adolescents was found to have limited impact on healthcare services in Norway. Preschool aged children might take longer to recover (3-6 months) than primary or secondary school students (1-3 months), usually because of respiratory conditions.

ObjectiveTo assess the risk of transmission of SARS-CoV-2 in schools in Norway mainly kept open during the covid-19 pandemic in the academic year 2020-21.DesignPopulation wide, register based cohort study.SettingPrimary and lower secondary schools in Norway open during the academic year 2020-21, with strict infection prevention and control measures in place, such as organisation of students into smaller cohorts. Contact tracing, quarantine, and isolation were also implemented, and testing of students and staff identified as close contacts.ParticipantsAll students and educational staff in primary and lower secondary schools in Norway, from August 2020 to June 2021.Main outcome measuresOverall attack rate of SARS-CoV-2 transmission (AR14) was defined as the number of individuals (among students, staff, or both) in the school with covid-19, detected within 14 days of the index case, divided by the number of students and staff members in the school. AR14 to students (attack rates from all index cases to students only) and AR14 to school staff (attack rates from all index cases to staff members only) were also calculated. These measures for student and school staff index cases were also calculated separately to explore variation in AR14 based on the characteristics of the index case.ResultsFrom August 2020 to June 2021, 4078 index cases were identified; 3220 (79%) students and 858 (21%) school staff. In most (2230 (55%)) schools with an index case, no subsequent individuals with covid-19 were found within 14 days; in 631 (16%) schools, only one more individual with covid-19 within 14 days was found. Overall, AR14 was 0.33% (95% confidence interval 0.32% to 0.33%). When restricting index cases and subsequent individuals with covid-19 to students born in the same year, AR14 to students (0.56-0.78%) was slightly higher.ConclusionsRegarding the number of people infected with SARS-CoV-2 among students and staff, these results suggest that schools were not an important setting for transmission of the virus in Norway during the covid-19 pandemic in the academic year 2020-21.

OBJECTIVES To compare effects of school closures with effects of targeted infection prevention and control (IPC) measures in open schools on SARS-CoV-2 infection rates in students. METHODS We conducted interrupted time-series analyses to compare trends in infection rates in grades 1–10 in 7 boroughs in Oslo, Norway, between February 15 and April 18, 2021. All schools at all levels had implemented strict IPC measures. While grades 1–4 attended school throughout the study period, school closures were implemented for grades 5–10 from March 17. We obtained individual level data from nationwide registries. RESULTS A total of 616, 452, and 446 students in grades 1–4, 5–7 and 8–10, respectively, were registered with a positive SARS-CoV-2 test during the study period, when the α-variant dominated. A statistically significant reduction in postintervention trends was observed for grades 1–4 (coefficient −1.26; 95% confidence interval (CI), −2.44 to −0.09). We did not observe any statistically significant between-group differences in postintervention trends between grades 1–4 and 5–7 (coefficient 0.66; 95% CI, −1.25 to 2.58) nor between grades 1–4 and 8–10 (coefficient −0.63; 95% CI, −2.30 to 1.04). Findings indicate that keeping schools open with strict IPC measures was equally effective as school closures on reducing student infection rates. CONCLUSIONS School closure was not more effective than targeted IPC measures in open schools in reducing student infection rates. Our findings suggest that keeping schools open with appropriate IPC measures should be preferred over school closures, considering the negative consequences closures have on students.

The acellular pertussis vaccine has been used in the Norwegian national immunisation program since 1998. Following an increase in pertussis incidence in all age groups, booster doses were introduced for 7-8-year-olds in 2006, and for 15-16-year-olds in 2013. We assessed the effects of the booster doses on pertussis incidence in different age groups to inform potential changes in vaccination policy.We included all pertussis cases notified to the Norwegian Surveillance System for Communicable Diseases in 1998-2019. We calculated annual incidence rates (IR, per 100,000 inhabitants) by age group. We estimated average annual changes in IRs (incidence rate ratios, IRR) for each age group for 2006-2012 and 2013-2019 using Poisson regression.In 1998-2019, 74,675 cases of pertussis were notified. Coinciding with booster introduction, between 2006 and 2012 the IR decreased among 8-15-year-olds (from 433 to 199/100,000, IRR 0.89 [95% confidence interval 0.88-0.90]). A similar decrease was seen between 2013 and 2019 among 16-19-year-olds (from 171 to 77/100,000, IRR 0.84 [0.82-0.86]). There was no significant change in IRs among children 1 year of age between 2006 and 2012 (IRR 0.99 [0.95-1.04]) or 2013-2019 (IRR 0.96 [0.91-1.02]). The IR decreased in both periods among adults aged 20-39 and 40+ (IRR 0.94 [0.93-0.95] and 0.92 [0.91-0.92] in 2006-2012; IRR 0.97 [0.96-0.99] and 0.97 [0.96-0.99] in 2013-2019, respectively). Despite steady, high vaccination coverage, in 2013-2019, there was an increase in the IR among children aged 1-7 (63 to 86/100,000, IRR 1.05 [1.03-1.07]) and 8-15 years (88 to 122/100,000, IRR 1.08 [1.06-1.10]).Pertussis booster doses have offered direct protection in the targeted age groups. Our findings suggest indirect protection in adults, while the incidence in infants hasn't changed. The recent increase in IRs among 1-15-year-olds warrants close monitoring and further evaluation of the vaccination schedule.

ObjectiveTo determine risk factors for SARS-CoV-2 infection and hospitalisation among children and adolescents.DesignNationwide, population-based cohort study. Setting: Norway from 1 March 2020 to 31 April 2021. Participants: All Norwegian residents Main outcome measuresPopulation-based health care and population registries were used to study risk factors for SARS-CoV-2 infection, including socioeconomic factors, country of origin, and pre-existing chronic comorbidities. All residents were followed until age 18, emigration, death, or end of follow-up. Hazard ratios (HR) estimated by Cox regression models were adjusted for testing frequency. Further, risk factors for admission to the hospital among the infected were investigated.ResultsOf 1 182 796 residents, 22608 (1.9%) tested positive by polymerase chain reaction or lateral flow tests, of whom 107 (0.5%) were admitted to a hospital. Low family income (aHR 1.40, 95% confidence interval 1.36 to 1.46), crowded housing (1.35, 1.30 to 1.39), household size, age, and area of living were independent risk factors for infection. A non-Nordic country of origin was the strongest risk factor (aHR 2.37, 95% CI 2.30 to 2.49), whereas chronic comorbidity was not associated with the risk of infection. Chronic comorbidity was associated with hospitalisation (aHR 4.15, 2.63 to 6.56), in addition to age, whereas socioeconomic status and country of origin did not predict hospitalisation among those infected.ConclusionsSocioeconomic factors, country of origin, and area of living were associated with the risk of SARS-CoV-2 infection. However, these factors did not predict hospitalisation among those infected. Chronic comorbidity was associated with the risk of admission but not with the overall risk of acquiring SARS-CoV-2.What is already known on this topicHospital admissions rates for covid-19 among children and adolescents are low compared to adults. Admission rates to hospitals and intensive care units for covid-19 have been higher in minority groups and in children and adolescents with chronic comorbidity.Whether underlying differences in susceptibility for severe disease or the incidence of infections are driving these associations have not been investigated.What this study addsLow family income, crowded housing and household size, and country of origin outside the Nordic countries were associated with increased risk of infection with SARS-CoV-2.None of these factors, but chronic comorbidities, were associated with the risk of hospital admission among those infected.

Pregnant women are recommended to receive COVID-19 vaccination to reduce risk of severe COVID-19. Whether vaccination during pregnancy also provides passive protection to infants after birth remains unclear.To determine whether COVID-19 vaccination in pregnancy was associated with reduced risk of COVID-19 in infants up to age 4 months during COVID-19 pandemic periods dominated by Delta and Omicron variants.This nationwide, register-based cohort study included all live-born infants born in Norway between September 1, 2021, and February 28, 2022.Maternal messenger RNA COVID-19 vaccination during second or third trimester compared with no vaccination before or during pregnancy.The risk of a positive polymerase chain reaction test result for SARS-CoV-2 during an infant's first 4 months of life by maternal vaccination status during pregnancy with either dose 2 or 3 was estimated, as stratified by periods dominated by the Delta variant (between September 1 and December 31, 2021) or Omicron variant (after January 1, 2022, to the end of follow-up on April 4, 2022). A Cox proportional hazard regression was used, adjusting for maternal age, parity, education, maternal country of birth, and county of residence.Of 21 643 live-born infants, 9739 (45.0%) were born to women who received a second or third dose of a COVID-19 vaccine during pregnancy. The first 4 months of life incidence rate of a positive test for SARS-CoV-2 was 5.8 per 10 000 follow-up days. Infants of mothers vaccinated during pregnancy had a lower risk of a positive test compared with infants of unvaccinated mothers and lower risk during the Delta variant-dominated period (incidence rate, 1.2 vs 3.0 per 10 000 follow-up days; adjusted hazard ratio, 0.29; 95% CI, 0.19-0.46) compared with the Omicron period (incidence rate, 7.0 vs 10.9 per 10 000 follow-up days; adjusted hazard ratio, 0.67; 95% CI, 0.57-0.79).The results of this Norwegian population-based cohort study suggested a lower risk of a positive test for SARS-CoV-2 during the first 4 months of life among infants born to mothers who were vaccinated during pregnancy. Maternal COVID-19 vaccination may provide passive protection to young infants, for whom COVID-19 vaccines are currently not available.

ObjectivesTo explore whether, and for how long COVID-19 among children gives an increase in use of health care services, when compared to children with no COVID-19.MethodsStudying all Norwegian residents aged 1-5, 6-15 and 16-19 years from August 1st2020 to February 1st2021 (N= 768 560), we contrasted rates of monthly all-cause primary and specialist health care use before and after testing for SARS-CoV-2 (% relative change), for children testing positive (non-hospitalized in the acute phase) (N=10 306) vs children with no COVID-19 (N=758 254).ResultsWe found a substantial elevation in short-term primary care use for children testing positive for SARS-CoV-2 during the first month following positive test when compared to children testing negative (relative elevation 1-5 years: 325%, 95%CI=296-354; 6-15 years: 434%, 95%CI=415-453; 16-19 years: 360%, 95%CI=342-379). There was still elevated primary care use at 2 months (1-5 years: 21%, 95%CI= 4-38; 6-15 years: 13%, 95%CI=2-25) and at 3 months (1-5 years: 26%, 95%CI=7-45, 6-15 years: 15%, 95%CI=3-26) for young children, but not at 2 or 3 months for the older children (16-19 years: 10%, 95%CI=-1-22 and 6%, 95%CI=-5-18, respectively). The 1-5-year-olds also had a long-term (up to 6 months) increase of primary care (14%, 95%CI=1-26) that was not observed for older age groups, when compared to same-aged children testing negative. We observed no elevated use of specialist care.ConclusionChildren in pre-school age used health services for a longer time (3-6 months) after COVID-19 than children in primary and secondary school age (1-3 months).

Background Reported transmission rates of SARS-CoV-2 within families vary widely, and there are few reports on transmission from children to other family members. More knowledge is needed to guide infection control measures. Objective To characterize the family index case for detected SARS-CoV-2 and describe testing and secondary attack rates in the family. Design Register-based cohort study. Setting Individual-level administrative data of all families and all PCR tests for SARS-CoV-2 in Norway in 2020. Participants All families with at least one parent and one child below the age of 20, who lived at the same address (N=662 582), where at least one member tested positive for SARS-CoV-2 in 2020. Main outcome measures Secondary attack rates (SAR7) were defined as the share of non-index family members with a positive PCR test within seven days of the index case. SARs were calculated separately for parent- and child-index cases, and for parent- and child-secondary cases. Results We identified 7548 index cases, comprising 26 991 individuals, of which 12184 were parents and 14808 children. The index was a parent in 66% of the cases. Among the children, 42% of the index cases were in the age group 17-20 and only 8% 0-6 years. When the index was a parent, SAR7 was 24% (95%CI 24 to 25), whilst SAR7 was 14% (95%CI 13 to 15) when the index was a child. However, SAR7 was 24% (95%CI 20 to 28) when the index was a child aged 0-6 years and declined steeply with increasing age of the index child. SAR7 from index parent to other parents was 35% (95%CI 33 to 36), and from index child to other children 12% (95%CI 11 to 13). SAR7 from index child aged 0-6 to parents was 27% (95%CI 22 to 33). The percent of non-index family members tested within 7 days after the index case, increased from about 20% in April to 80% in December, however, SAR7 stabilized at about 20% from May. Conclusion Parents and older children are most often index cases for SARS-CoV-2 in families in Norway, while parents and young children more often transmit the virus within the families. This study suggests that whilst the absolute infection numbers are low for young children because of their low introduction rate, when infected, young children and parents transmit the virus to the same extent within the family.

Stricter infection controls and school closures to tackle COVID-19 are regularly called for in the public discourse on the pandemic. However, restrictions on schooling and leisure activities can have negative consequences. Norwegian and international data appear to support the argument to keep schools and day-care centres open, with good infection control measures, and that closing them should be a last resort.

An intense debate on school closures to control the COVID-19 pandemic is ongoing in Europe. We prospectively examined transmission of SARS-CoV-2 from confirmed paediatric cases in Norwegian primary schools between August and November 2020. All in-school contacts were systematically tested twice during their quarantine period. With preventive measures implemented in schools, we found minimal child-to-child (0.9%, 2/234) and child-to-adult (1.7%, 1/58) transmission, supporting that under 14 year olds are not the drivers of SARS-CoV-2 transmission.

The role of children in the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in schools has been a topic of controversy. In this study among school contacts of SARS-CoV-2 positive children in 43 contact-investigations, we investigated SARS-CoV-2 transmission in Norway, August 2020–May 2021. All participants were tested twice within seven to ten days, using SARS-CoV-2 PCR on home-sampled saliva. Positive samples were whole genome sequenced. Among the 559 child contacts, eight tested positive (1.4%, 95% CI 0.62–2.80), with no significant difference between primary (1.0%, 95% CI 0.27–2.53) and secondary schools (2.6%, 95% CI 0.70–6.39), p = 0.229, nor by viral strain, non-Alpha (1.4%, 95% CI 0.50–2.94) and Alpha variant (B.1.1.7) (1.7%, 95% CI 0.21–5.99), p = 0.665. One adult contact (1/100) tested positive. In 34 index cases, we detected 13 different SARS-CoV-2 Pango lineage variants, with B.1.1.7 being most frequent. In the eight contact-investigations with SARS-CoV-2 positive contacts, four had the same sequence identity as the index, one had no relation, and three were inconclusive. With mitigation measures in place, the spread of SARS-CoV-2 from children in schools is limited. By excluding contact-investigations with adult cases known at the time of enrolment, our data provide a valid estimate on the role of children in the transmission of SARS-CoV-2 in schools.

Children and adolescents are at lower risk of disease caused by SARS-CoV-2. We describe the incidence of confirmed infection and hospitalisation of children and adolescents under the age of 20 in Norway, and specifically among those with underlying conditions.The Norwegian Directorate of Health has collaborated with the Norwegian Institute of Public Health on the establishment of a data extraction system to monitor the coronavirus outbreak. Data from the specialist health service (Norwegian Patient Registry, NPR), and the primary health service (Norwegian Registry for Primary Health Care, NRPHC) are linked to data on positive SARS-CoV-2 tests from the Surveillance System for Communicable Diseases (MSIS). This covers all persons living in Norway as of 1 March 2020, with data on confirmed infection up to and including 13 May 2020 and on hospitalisations up to and including 30 April 2020.Of 8 125 persons with confirmed SARS-CoV-2 in the whole population, 493 (6.1 %) were under 20 years old. The median age of the under-20s was 15 years, and 252 (51 %) were girls. 3 % were hospitalised. No deaths were registered among patients aged under 20 in Norway. We found a somewhat larger share with confirmed SARS-CoV-2 in the group with diseases of the neuromuscular system.Few children and adolescents have had SARS-CoV-2 confirmed, and only a very few have been hospitalised. Underlying conditions may result in a lower threshold for testing, and hence a higher incidence of confirmed infection in this group, although higher risk cannot be excluded.

In response to the coronavirus disease (COVID-19) pandemic, most countries implemented school closures. In Norway, schools closed on 13 March 2020. The evidence of effect on disease transmission was limited, while negative consequences were evident. Before reopening, risk-assessment for paediatric risk groups was performed, concluding that most children can attend school with few conditions requiring preventative homeschooling. We here present infection prevention and control guidelines for primary schools and recommendations for paediatric risk groups.

Background Children and adolescents are at lower risk of disease caused by SARS-CoV-2. We describe the incidence of confirmed infection and hospitalisation of children and adolescents under the age of 20 in Norway, and specifically among those with underlying conditions. Material and method The Norwegian Directorate of Health has collaborated with the Norwegian Institute of Public Health on the establishment of a data extraction system to monitor the coronavirus outbreak. Data from the specialist health service (Norwegian Patient Registry, NPR), and the primary health service (Norwegian Registry for Primary Health Care, NRPHC) are linked to data on positive SARS-CoV-2 tests from the Surveillance System for Communicable Diseases (MSIS). This covers all persons living in Norway as of 1 March 2020, with data on confirmed infection up to and including 13 May 2020 and on hospitalisations up to and including 30 April 2020. Results Of 8 125 persons with confirmed SARS-CoV-2 in the whole population, 493 (6.1 %) were under 20 years old. The median age of the under-20s was 15 years, and 252 (51 %) were girls. 3 % were hospitalised. No deaths were registered among patients aged under 20 in Norway. We found a somewhat larger share with confirmed SARS-CoV-2 in the group with diseases of the neuromuscular system. Interpretation Few children and adolescents have had SARS-CoV-2 confirmed, and only a very few have been hospitalised. Underlying conditions may result in a lower threshold for testing, and hence a higher incidence of confirmed infection in this group, although higher risk cannot be excluded.

Background Vaccination has been suggested to be involved in the aetiology of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). HPV vaccine was introduced in the Norwegian Childhood Immunisation Programme and offered 12 year old girls from 2009. We studied the association between HPV vaccination and risk of CFS/ME and also assessed medical history in relation to both risk of CFS/ME and HPV vaccine uptake. Methods Individual data from national registries, including the Norwegian Population Registry, the Norwegian Patient Registry and the Norwegian Immunisation Registry were linked using the unique personal identification number. Yearly incidence rates of CFS/ME for 2009–2014 were calculated among the 824,133 boys and girls, aged 10–17 living in Norway during these 6 years. A total of 176,453 girls born 1997–2002 were eligible for HPV vaccination and included in further analyses. Hazard ratios (HRs) of CFS/ME were estimated using Cox regression. Risk differences (RDs) of vaccine uptake were estimated with binomial regression. Results A similar yearly increase in incidence rate of CFS/ME was observed among girls and boys, IRR = 1.15 (95% confidence interval (CI) 1.10–1.19) and 1.15 (95% CI 1.09–1.22), respectively. HPV vaccination was not associated with CFS/ME, HR = 0.86 (95% CI 0.69–1.08) for the entire follow-up period and 0.96 (95% CI 0.64–1.43) for the first two years after vaccination. The risk of CFS/ME increased with increasing number of previous hospital contacts, HR = 5.23 (95% CI 3.66–7.49) for 7 or more contacts as compared to no contacts. Girls with 7 or more hospital contacts were less likely to be vaccinated than girls with no previous hospital contacts, RD = −5.5% (95% CI −6.7% to −4.2%). Conclusions No indication of increased risk of CFS/ME following HPV vaccination was observed among girls in the first 6 birth cohorts offered HPV vaccine through the national immunisation programme in Norway.

Introduction Pertussis outbreaks have occurred in several industrialised countries using acellular pertussis vaccines (ACVs) since the 1990s. High prevalence of pertactin (PRN)-deficient Bordetella pertussis isolates has been found in these countries. Aims To evaluate in Europe: (i) whether proportions of PRN-deficient strains increased in consecutive collections of B. pertussis clinical isolates; (ii) if the frequency of PRN-deficient strains in countries correlated with the time since ACV introduction; (iii) the presence of pertussis toxin (PT)-, filamentous haemagglutinin (FHA)- or fimbriae (Fim)-deficient isolates. Methods B. pertussis clinical isolates were obtained from different European countries during four periods (EUpert I–IV studies): 1998 to 2001 (n = 102), 2004 to 2005 (n = 154), 2007 to 2009 (n = 140) and 2012 to 2015 (n = 265). The isolates’ selection criteria remained unchanged in all periods. PRN, PT, FHA and Fim2 and Fim3 expression were assessed by ELISA. Results In each period 1.0% (1/102), 1.9% (3/154), 6.4% (9/140) and 24.9% (66/265) of isolates were PRN-deficient. In EUpert IV, PRN-deficient isolates occurred in all countries sampled and in six countries their frequency was higher than in EUpert III (for Sweden and the United Kingdom, p Conclusion Results suggest that the longer the period since the introduction of ACVs containing PRN, the higher the frequency of circulating PRN-deficient isolates.

From 6 September 2015–May 2016, a large mumps outbreak occurred among vaccinated students in Norway. A case was defined as a person presenting with a clinical mumps infection, notified between 1 September 2015 and 30 June 2016. Confirmed cases had positive laboratory confirmation and probable cases had an epidemiological link; PCR-positive specimens were genotyped. A total of 232 cases were notified (230 confirmed) with median age of 23 years (range 4–81) and 61% were male. Of 68 (30%) confirmed cases that were genotyped, 66 were genotype G and associated with the outbreak. Cases that had received two doses of the measles-mumps-rubella (MMR) vaccine had reduced risk of hospitalisation (adjusted relative risk (aRR): 0.14; 95%CI: 0.03–0.57), mumps-related orchitis (aRR: 0.21; 95% CI: 0.08–0.55) and severe outcome (aRR: 0.25; 95% CI: 0.10–0.62) compared with those unvaccinated. A third dose of the vaccine was offered to approximately 1,300 fully vaccinated close contacts and subsequently reported cases decreased. This large outbreak, occurring among predominately vaccinated students, suggests the current genotype A vaccine offers suboptimal protection against mumps genotype G. We recommend maintaining high vaccination coverage and offering the vaccine to all unvaccinated individuals. This article is copyright of the authors, 2018. This work is licensed under a Creative Commons Attribution 4.0 International License.

One reason for increased pertussis incidence is the adaptation of Bordetella pertussis to vaccine-induced immunity by modulating its genomic structure. This study, EUpert IV, includes 265 isolates collected from nine European countries during 2012 to 2015 ( n = 265) and compares the results to previous EUpert I to III studies (1998 to 2009). The analyses included genotyping, serotyping, pulsed-field gel electrophoresis (PFGE), and multilocus variable-number tandem-repeat analysis (MLVA). Genotyping results showed only small variations among the common virulence genes of B. pertussis . The frequencies of serotypes Fim2 and Fim3 varied among the four collections. Genomic analyses showed that MLVA type 27 increased to 80% between the periods of 1998 to 2001 and 2012 to 2015. Two PFGE profiles, BpSR3 (29.4%) and BpSR10 (27.2%), constituted more than 50% of the circulating isolates in the present collection. Our study indicates that the European B. pertussis population is changing and became more homogenous after the introduction of acellular pertussis vaccines.

T cells mediating a graft-versus-leukemia/lymphoma effects without causing graft-versus-host disease would greatly improve the safety and applicability of hematopoietic stem cell transplantation. We recently demonstrated that highly peptide- and HLA-specific T cells can readily be generated against allogeneic HLA-A*02:01 in complex with a peptide from the B cell-restricted protein CD20. Here, we show that such CD20-specific T cells can easily be induced from naïve precursors in cord blood, demonstrating that they do not represent cross-reactive memory cells. The cells displayed high avidity and mediated potent cytotoxic effects on cells from patients with the CD20(pos) B cell malignancies follicular lymphoma (FL) and acute lymphoblastic leukemia (ALL). However, the cytotoxicity was consistently lower for cells from two of the ALL patients. The ALL cells that were less efficiently killed did not display lower surface expression of CD20 or HLA-A*02:01, or mutations in the CD20 sequence. Peptide pulsing fully restored the levels of cytotoxicity, indicating that they are indeed susceptible to T cell-mediated killing. Adoptive transfer of CD20-specific T cells to an HLA-A*02:01(pos) patient requires an HLA-A*02:01(neg) , but otherwise HLA identical, donor. A search clarified that donors meeting these criteria can be readily identified even for patients with rare haplotypes. The results bear further promise for the clinical utility of CD20-specific T cells in B cell malignancies.

Our objective was to describe clinical and laboratory characteristics, treatment and outcome among Norwegian children with cancer suffering from chemotherapy-induced febrile neutropenia (FN). We retrospectively reviewed data on paediatric FN episodes in 7 Norwegian hospitals during a 2.5-y period. A total of 236 episodes of FN occurred in 95 children. Acute lymphoblastic leukaemia was the most common diagnosis (49 patients). Blood cultures yielded growth in 39 episodes (17%). Primary empirical antibiotic regimens could be assigned to 2 main groups: 1) benzylpenicillin or ampicillin and an aminoglycoside (58%) or 2) a regimen based on third-generation cephalosporins (42%). There were no statistically significant differences in outcome between the 2 regimens in terms of need to change initial antibiotic treatment, d of fever or maximum C-reactive protein values. One infection-related death (fungal septicaemia) occurred during the study period. We conclude that incidence of septicaemia and clinical outcome is similar to recent international trials on paediatric FN, but antibiotic treatment in Norway differs from international guidelines. However, patients in our study were successfully and safely treated, irrespective of the primary empirical antibiotic regimen.

Background: Approximately 10 % of Norwegian newborns are each year transferred to a Neonatal Intensive Care Unit (NICU). They experience pain from numerous sources and their pain is often poorly managed. Aims: To describe health personnel?? opinions, knowledge and view of potential barriers in neonatal pain management. Materials and methods: Physicians (n=20), nurses (n=53) and nurse assistants (n=17) from two Norwegian NICUs participated. Response rate 81 %. A structured questionnaire was developed, based on an extensive literature search. Approval from the ethical committee of Southern Norway was obtained. Non-parametric statistical tests were used. Results: The respondents acquired their knowledge mainly from work place experience. Lack of knowledge was percieved as a barrier by more nurses than phycicians. Respondents see insufficient pain assessment as a barrier. Health personnel's competence in use of analgesics and comfort measures differ. The views are diverse regarding to what extent prescription and administration of analgesics are barriers to effective pain management. Conclusion: Knowledge is mainly acquired through work place experience and health personnel evaluate their competence as partly insufficient. Lack of knowledge and deficiencies in pain assessment and management were considered as barriers in pain management practices.

Aim: Neonates are subjected to numerous painful procedures without sufficient pain management. The aim of this study was to describe the opinions of Norwegian physicians, nurses and nurse assistants who care for neonates, regarding procedural pain in neonates. Methods: A replication of a previous questionnaire study was conducted in two Norwegian neonatal intensive care units (NICU's). The questionnaire aimed at evaluating procedure painfulness, the current use of pharmacological agents and comfort measures and the optimal use of both. Results: Ninety members of the clinical staff participated, which is a response rate of 87%. Opinions on how procedural pain is currently and optimally managed differed significantly. Although most respondents rated a majority of the listed procedures as being more than moderately painful, pharmacological agents were rarely used, except for the insertion of a chest tube and endotracheal intubation. Comfort measures were also believed to be underutilized, but not to the same degree as pharmacological agents. Conclusion: Procedural pain in neonates is not sufficiently managed and both pharmacological agents and comfort measures are underutilized, according to clinicians at two Norwegian NICU's.

Aim: Neonates are subjected to numerous painful procedures without sufficient pain management. The aim of this study was to describe the opinions of Norwegian physicians, nurses and nurse assistants who care for neonates, regarding procedural pain in neonates. Methods: A replication of a previous questionnaire study was conducted in two Norwegian neonatal intensive care units (NICU's). The questionnaire aimed at evaluating procedure painfulness, the current use of pharmacological agents and comfort measures and the optimal use of both. Results: Ninety members of the clinical staff participated, which is a response rate of 87%. Opinions on how procedural pain is currently and optimally managed differed significantly. Although most respondents rated a majority of the listed procedures as being more than moderately painful, pharmacological agents were rarely used, except for the insertion of a chest tube and endotracheal intubation. Comfort measures were also believed to be underutilized, but not to the same degree as pharmacological agents. Conclusion: Procedural pain in neonates is not sufficiently managed and both pharmacological agents and comfort measures are underutilized, according to clinicians at two Norwegian NICU's.