Search

Testing humans for infectious diseases is often done by assessing the presence or absence of disease-specific antibodies in serum samples. For feasibility and economical reasons, these sera are often tested for more than one antigen. Studying diseases with similar transmission routes can govern new insights for disease dynamics. We use flexible marginal and conditional models to model multisera data on the Varicella-Zoster virus and the Parvo B19-virus in Belgium. Next form the derivation of the age-dependent marginal force of infection (FOI), we introduce new epidemiological parameters: the age-dependent joint and conditional FOI. These parameters allow us to study the association among the occurrence and acquisition of both infections. Furthermore, we show how to test for association and whether the infection-specific age-dependent FOI curves are proportional and consequently whether separable mixing in the population holds. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objective: To evaluate immunogenicity and reactogenicity of primary vaccination with reduced-antigen-content diphtheria-tetanus-acellular pertussis (dTpa) or dTpa-inactivated poliovirus (dTpa-IPV) vaccine compared to diphtheria-tetanus-toxoid vaccines (Td) in adults > or = 40 years of age without diphtheria or tetanus vaccination for 20 years or with an unknown vaccination history.Research Design and Methods: Double-blind, randomized, controlled clinical trial. Primary vaccination with either three doses of dTpa, one dose of dTpa-IPV followed by two doses of Td, or three doses of Td vaccine (control) administered in a 0-1-6-month schedule.Main Outcome Measures: Blood samples were collected before commencement and 1 month after each dose. Local and general symptoms were solicited for 15 days after each dose.Results: A total of 460 adults were enrolled, of whom over 48% did not have protective antibody concentrations against diphtheria and tetanus. One month after dose 3 > 99% had seroprotective anti-diphtheria and tetanus antibodies. Three doses were required to maximize anti-diphtheria seroprotection rates. A vaccine response to pertussis antigens was observed in > 92% of dTpa and dTpa-IPV recipients after dose 1. One month after dTpa-IPV, > 98.4% had seroprotective anti-polio titres. No statistically significant differences in local or general symptoms between groups were observed.Conclusions: dTpa and dTpa-IPV can provide primary vaccination of adults. Combinations of dTpa or dTpa-IPV can be used to replace Td and provide booster vaccination against pertussis and polio simultaneously with diphtheria and tetanus, even in situations where the primary vaccination history is unknown. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To evaluate age-specific measles susceptibility in Australia and 17 European countries. METHODS: As part of the European Sero-Epidemiology Network 2 (ESEN2), 18 countries collected large national serum banks between 1996 and 2004. These banks were tested for measles IgG and the results converted to a common unitage to enable valid intercountry comparisons. Historical vaccination and disease incidence data were also collected. Age-stratified population susceptibility levels were compared to WHO European Region targets for measles elimination of < 15% in those aged 2-4 years, < 10% in 5-9-year-olds and < 5% in older age groups. FINDINGS: Seven countries (Czech Republic, Hungary, Luxembourg, Spain, Slovakia, Slovenia and Sweden) met or came very close to the elimination targets. Four countries (Australia, Israel, Lithuania and Malta) had susceptibility levels above WHO targets in some older age groups indicating possible gaps in protection. Seven countries (Belgium, Bulgaria, Cyprus, England and Wales, Ireland, Latvia and Romania) were deemed to be at risk of epidemics as a result of high susceptibility in children and also, in some cases, adults. CONCLUSION: Although all countries now implement a two-dose measles vaccination schedule, if the WHO European Region target of measles elimination by 2010 is to be achieved higher routine coverage as well as vaccination campaigns in some older age cohorts are needed in some countries. Without these improvements, continued measles transmission and outbreaks are expected in Europe. Copyright © 2008 World Health Organization [ABSTRACT FROM AUTHOR]

OBJECTIVE: To standardize serological surveillance to compare rubella susceptibility in Australia and 16 European countries, and measure progress towards international disease-control targets. METHODS: Between 1996 and 2004, representative serum banks were established in 17 countries by collecting residual sera or community sampling. Serum banks were tested in each country and assay results were standardized. With a questionnaire, we collected information on current and past rubella vaccination programmes in each country. The percentage of seronegative (< 4 IU/ml) children (2-14 years of age) was used to evaluate rubella susceptibility, and countries were classified by seronegativity as group I (< 5%), group II (5-10%) or group III (> 10%). The proportion of women of childbearing age without rubella protection (< or = 10 IU/ml) was calculated and compared with WHO targets of < 5%. FINDINGS: Only Romania had no rubella immunization programme at the time of the survey; the remaining countries had a two-dose childhood schedule using the measles, mumps and rubella (MMR) vaccine. The percentage of susceptible children defined five countries as group I, seven as group II and four as group III. Women of childbearing age without rubella protection were < 5% in only five countries. CONCLUSION: Despite the low reported incidence in many countries, strengthening the coverage of the routine two-dose of MMR vaccine among children is needed, especially in group III countries. Catch-up campaigns in older age groups and selective targeting of older females are needed in many countries to ensure necessary levels of protective immunity among women of childbearing age. Copyright © 2008 World Health Organization [ABSTRACT FROM AUTHOR]

Background: Non-typeable Haemophilus influenzae has become increasingly important as a causative agent of invasive diseases following vaccination against H. influenzae type b. The emergence of antibiotic resistance underscores the necessity to investigate typeable non-b carriage and non-typeable H. influenzae (NTHi) in children., Methods: Nasopharyngeal swab samples were taken over a three-year period (2016-2018) from 336 children (6-30 months of age) attending daycare centers (DCCs) in Belgium, and from 218 children with acute otitis media (AOM). Biotype, serotype, and antibiotic resistance of H. influenzae strains were determined phenotypically. Mutations in the ftsI gene were explored in 129 strains that were resistant or had reduced susceptibility to beta-lactam antibiotics. Results were compared with data obtained during overlapping time periods from 94 children experiencing invasive disease., Results: Overall, NTHi was most frequently present in both carriage (DCC, AOM) and invasive group. This was followed by serotype "f" (2.2%) and "e" (1.4%) in carriage, and "b" (16.0%), "f" (11.7%), and "a" (4.3%) in invasive strains. Biotype II was most prevalent in all studied groups, followed by biotype III in carriage and I in invasive strains. Strains from both groups showed highest resistance to ampicillin (26.7% in carriage vs. 18.1% in invasive group). A higher frequency of ftsI mutations were found in the AOM group than the DCC group (21.6 vs. 14.9% - p  = 0.056). Even more so, the proportion of biotype III strains that carried a ftsI mutation was higher in AOM compared to DCC (50.0 vs. 26.3% - p  < 0.01) and invasive group., Conclusion: In both groups, NTHi was most frequently circulating, while specific encapsulated serotypes for carriage and invasive group were found. Biotypes I, II and III were more frequently present in the carriage and invasive group. The carriage group had a higher resistance-frequency to the analyzed antibiotics than the invasive group. Interestingly, a higher degree of ftsI mutations was found in children with AOM compared to DCC and invasive group. This data helps understanding the H. influenzae carriage in Belgian children, as such information is scarce., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Ekinci, Willen, Rodriguez Ruiz, Maertens, Van Heirstraeten, Serrano, Wautier, Deplano, Goossens, Van Damme, Beutels, Malhotra-Kumar, Martiny and Theeten.)

Background: Pneumococcal conjugate vaccines (PCVs) effectively reduce infection and asymptomatic carriage of Streptococcus pneumoniae vaccine serotypes. In 2016, Belgium replaced its infant PCV13 program by a 4-year period of PCV10. Concomitantly, S. pneumoniae serotype carriage was monitored together with the carriage of other nasopharyngeal pathogens in children attending day-care centers., Methods: From 2016 to 2019, a total of 3459 nasopharyngeal swabs were obtained from children aged 6-30 months. Culture and qPCR were used for the identification of S. pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Staphylococcus aureus and for serotyping and antimicrobial susceptibility assessment of S. pneumoniae strains., Results: S. pneumoniae colonization was frequent and stable over the study years. H. influenzae and M. catarrhalis were more frequently carried (P < .001) than S. pneumoniae, by, respectively, 92.3% and 91.0% of children. Prevalence of all PCV13 serotypes together increased significantly over time from 5.8% to 19.6% (P < .001) and was attributable to the increasing prevalence of serotype 19A. Coincidently, non-vaccine serotype 6C increased (P < .001) and the overall pneumococcal non-susceptibility to tetracycline and erythromycin. Non-susceptibility to cotrimoxazole decreased (P < .001)., Conclusions: The switch to a PCV program no longer covering serotypes 19A, 6A, and 3 was associated with a sustained increase of serotypes 19A and 6C in healthy children, similarly as in invasive pneumococcal disease. This resulted in a re-introduction of the 13-valent conjugate vaccine during the summer of 2019., (© The Author(s) 2022. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society.)

Introduction: Long term care facilities for elderly (LTCFs) in Europe encountered a high disease burden at the start of the COVID-19 pandemic. Therefore, these facilities were the first to receive COVID-19 vaccines in many European countries. A limited COVID-19 vaccine supply early 2021 resulted in a majority of residents and healthcare workers (HCWs) in LTCFs being vaccinated compared to a minority in the general population. This study exploits this imbalance to assess the efficiency of COVID-19 vaccination in containing outbreaks in LTCFs., Methods: Exploratory statistics were performed using data from a COVID-19 surveillance system covering all 842 LTCFs in Flanders (the northern region of Belgium). The number and size of COVID-19 outbreaks in LTCFs were compared (1) before and after introducing vaccines and (2) with the status of the pandemic in the general population. Based on individual data from 15 LTCFs, the infection rate and symptoms of vaccinated and unvaccinated residents and HCWs were compared during a COVID-19 outbreak., Results: 95.8% of the residents and 90.9% of the HCWs in Flemish LTCFs were vaccinated before May 30, 2021. Before vaccine introduction, residents in LTCFs were 10 times more likely to test positive for COVID-19 than the general population of Flanders. This ratio reversed after vaccination. Furthermore, after vaccination fewer and shorter outbreaks were observed involving fewer residents. During these outbreaks, vaccinated and unvaccinated residents were equally likely to test positive, but positive vaccinated residents were less likely to develop severe symptoms. In contrast, unvaccinated HCWs were more likely to test positive., Conclusion: In the first half of 2021, two-dose vaccination was highly efficient in preventing and containing outbreaks in LTCFs, reducing COVID-19 hospitalizations and deaths. The high likelihood of unvaccinated HCWs to be involved in COVID-19 outbreaks in vaccinated LTCFs emphasizes the importance of vaccinating HCWs., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The universities of Hasselt and Antwerp received funding for grants from GSK Biologicals, Pfizer, Merck and J&J, outside the submitted work., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

After switching from 13-valent to 10-valent pneumococcal conjugate vaccine (PCV10) (2015-2016) for children in Belgium, we observed rapid reemergence of serotype 19A invasive pneumococcal disease (IPD). Whole-genome sequencing of 166 serotype 19A IPD isolates from children (n = 54) and older adults (n = 56) and carriage isolates from healthy children (n = 56) collected after the vaccine switch (2017-2018) showed 24 sequence types (STs). ST416 (global pneumococcal sequence cluster [GPSC] 4) and ST994 (GPSC146) accounted for 75.9% of IPD strains from children and 65.7% of IPD (children and older adults) and carriage isolates in the PCV10 period (2017-2018). These STs differed from predominant 19A IPD STs after introduction of PCV7 (2011) in Belgium (ST193 [GPSC11] and ST276 [GPSC10]), which indicates that prediction of emerging strains cannot be based solely on historical emerging strains. Despite their susceptible antimicrobial drug profiles, these clones spread in carriage and IPD during PCV10 use.

Vaccine-preventable diseases, such as measles, have been re-emerging in countries with moderate to high vaccine uptake. It is increasingly important to identify and close immunity gaps and increase coverage of routine childhood vaccinations, including two doses of the measles-mumps-rubella vaccine (MMR). Here, we present a simple cohort model relying on a Bayesian approach to evaluate the evolution of measles seroprevalence in Belgium using the three most recent cross-sectional serological survey data collections (2002, 2006 and 2013) and information regarding vaccine properties. We find measles seroprevalence profiles to be similar for the different regions in Belgium. These profiles exhibit a drop in seroprevalence in birth cohorts that were offered vaccination at suboptimal coverages in the first years after routine vaccination has been started up. This immunity gap is observed across all cross-sectional survey years, although it is more pronounced in survey year 2013. At present, the COVID-19 pandemic could negatively impact the immunization coverage worldwide, thereby increasing the need for additional immunization programs in groups of children that are impacted by this. Therefore, it is now even more important to identify existing immunity gaps and to sustain and reach vaccine-derived measles immunity goals., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Niel Hens reports financial support was provided by European Research Council. Julie Schenk reports financial support was provided by European Research Council. Niel Hens reports a relationship with GSK. Niel Hens reports a relationship with Pfizer Inc. Niel Hens reports a relationship with Johnson & Johnson. Heidi Theeten reports a relationship with Pfizer Inc., (Copyright © 2022. Published by Elsevier Ltd.)

Presence of SARS-CoV-2 was monitored in nasopharyngeal samples from young children aged 6-30 months attending day-care centres (DCCs) in Belgium from May 2020-February 2022. SARS-CoV-2 carriage among DCC children was only detected from November 2021, after emergence of Delta and Omicron variants, in 9 of the 42 DCCs screened. In only one DCC, two children tested positive for SARS-CoV-2 at the same sampling time point, suggesting limited transmission of SARS-CoV-2 in Belgian DCCs among young children during the studied period.

BackgroundTo control epidemic waves, it is important to know the susceptibility to SARS-CoV-2 and its evolution over time in relation to the control measures taken.AimTo assess the evolving SARS-CoV-2 seroprevalence and seroincidence related to the first national lockdown in Belgium, we performed a nationwide seroprevalence study, stratified by age, sex and region using 3,000-4,000 residual samples during seven periods between 30 March and 17 October 2020.MethodsWe analysed residual sera from ambulatory patients for IgG antibodies against the SARS-CoV-2 S1 protein with a semiquantitative commercial ELISA. Weighted seroprevalence (overall and by age category and sex) and seroincidence during seven consecutive periods were estimated for the Belgian population while accommodating test-specific sensitivity and specificity.ResultsThe weighted overall seroprevalence initially increased from 1.8% (95% credible interval (CrI): 1.0-2.6) to 5.3% (95% CrI: 4.2-6.4), implying a seroincidence of 3.4% (95% CrI: 2.4-4.6) between the first and second collection period over a period of 3 weeks during lockdown (start lockdown mid-March 2020). Thereafter, seroprevalence stabilised, however, significant decreases were observed when comparing the third with the fifth, sixth and seventh period, resulting in negative seroincidence estimates after lockdown was lifted. We estimated for the last collection period mid-October 2020 a weighted overall seroprevalence of 4.2% (95% CrI: 3.1-5.2).ConclusionDuring lockdown, an initially small but increasing fraction of the Belgian population showed serologically detectable signs of exposure to SARS-CoV-2, which did not further increase when confinement measures eased and full lockdown was lifted.

BackgroundCOVID-19 mortality, excess mortality, deaths per million population (DPM), infection fatality ratio (IFR) and case fatality ratio (CFR) are reported and compared for many countries globally. These measures may appear objective, however, they should be interpreted with caution.AimWe examined reported COVID-19-related mortality in Belgium from 9 March 2020 to 28 June 2020, placing it against the background of excess mortality and compared the DPM and IFR between countries and within subgroups.MethodsThe relation between COVID-19-related mortality and excess mortality was evaluated by comparing COVID-19 mortality and the difference between observed and weekly average predictions of all-cause mortality. DPM were evaluated using demographic data of the Belgian population. The number of infections was estimated by a stochastic compartmental model. The IFR was estimated using a delay distribution between infection and death.ResultsIn the study period, 9,621 COVID-19-related deaths were reported, which is close to the excess mortality estimated using weekly averages (8,985 deaths). This translates to 837 DPM and an IFR of 1.5% in the general population. Both DPM and IFR increase with age and are substantially larger in the nursing home population.DiscussionDuring the first pandemic wave, Belgium had no discrepancy between COVID-19-related mortality and excess mortality. In light of this close agreement, it is useful to consider the DPM and IFR, which are both age, sex, and nursing home population-dependent. Comparison of COVID-19 mortality between countries should rather be based on excess mortality than on COVID-19-related mortality.

Streptococcus pneumoniae is an important and frequently carried respiratory pathogen that has the potential to cause serious invasive diseases, such as pneumonia, meningitis, and sepsis. Young children and older adults are among the most vulnerable to developing serious disease. With the arrival of the COVID-19 pandemic and the concomitant restrictive measures, invasive disease cases caused by respiratory bacterial species, including pneumococci, decreased substantially. Notably, the stringency of the containment measures as well as the visible reduction in the movement of people appeared to coincide with the drop in invasive disease cases. One could argue that wearing protective masks and adhering to social distancing guidelines to halt the spread of the SARS-CoV-2 virus, also led to a reduction in the person-to-person transmission of respiratory bacterial species. Although plausible, this conjecture is challenged by novel data obtained from our nasopharyngeal carriage study which is performed yearly in healthy daycare center attending children. A sustained and high pneumococcal carriage rate was observed amid periods of stringent restrictive measures. This finding prompts us to revisit the connection between nasopharyngeal colonization and invasion and invites us to look closer at the nasopharyngeal microbiome as a whole., Competing Interests: SD and HT received an investigator-initiated research grant from Pfizer. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Willen, Ekinci, Cuypers, Theeten and Desmet.)