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BACKGROUND: The introduction of the 7-valent conjugate pneumococcal vaccine (PCV7) in children may result in serotype replacement. We estimated the rate of increase of invasive pneumococcal disease (IPD) caused by serotype 19A in children <5 years old and determined the genetic composition of these isolates. METHODS: Cases of IPD between July 1999 and June 2004 were identified through the Active Bacterial Core Surveillance. Serotype 19A isolates obtained from children <5 years old between January 2003 and June 2004 were characterized by serotyping, antibiotic susceptibility testing, and pulsed-field gel electrophoresis (PFGE). Select isolates representing homologous PFGE clusters were subjected to multilocus sequence typing, and eBURST was used to delineate clonal groups. RESULTS: Between July 1999 and June 2004, the overall rate of IPD decreased from 23.3 to 13.1 cases/100,000 population (P<.00001). In children <5 years old, the rate decreased from 88.7 to 22.4 cases/100,000 population (P<.00001), whereas the rate in persons > or =5 years old decreased from 18.4 to 12.4 cases/100,000 population (P<.0001). The rate of serotype 19A IPD in children <5 years old increased significantly from 2.6 cases/100,000 population in 1999-2000 to 6.5 cases/100,000 population in 2003-2004; this was accompanied by significant increases in penicillin nonsusceptibility (P=.008) and multidrug resistance (P=.002) among serotype 19A isolates. As was observed during the pre-PCV7 era, clonal complex (CC) 199 predominated within serotype 19A, representing approximately 70% of invasive serotype 19A isolates from children <5 years old during 2003-2004. New serotype 19A genotypes were observed during 2003-2004, including 6 CCs that were not found among pneumococcal serotype 19A isolates during surveillance in 1999. CONCLUSION: Serotype 19A is, at present, the most important cause of IPD by replacement serotypes, and it is increasingly drug resistant. CC199 is the predominant CC among type 19A serotypes in children <5 years old. Our data suggest that some of the increase in rates of infection with serotype 19A may be due to serotype switching within certain vaccine type strains. Copyright © 2005 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

OBJECTIVE: We conducted a case-control study to evaluate risk factors for invasive pneumococcal disease (IPD) among children who were aged 3 to 59 months in the era of pneumococcal conjugate vaccine (PCV7). METHODS: IPD cases were identified through routine surveillance during 2001-2004. We matched a median of 3 control subjects to each case patient by age and zip code. We calculated odds ratios for potential risk factors for vaccine-type and non-vaccine-type IPD by using multivariable conditional logistic regression. RESULTS: We enrolled 782 case patients (45% vaccine-type IPD) and 2512 matched control subjects. Among children who received any PCV7, children were at increased risk for vaccine-type IPD when they had underlying illnesses, were male, or had no health care coverage. Vaccination with PCV7 did not influence the risk for non-vaccine-type IPD. Presence of underlying illnesses increased the risk for non-vaccine-type IPD, particularly among children who were not exposed to household smoking. Non-vaccine-type case patients were more likely than control subjects to attend group child care, be male, live in low-income households, or have asthma; case patients were less likely than control subjects to live in households with other children. CONCLUSIONS: Vaccination with PCV7 has reduced the risk for vaccine-type IPD that is associated with race and group child care attendance. Because these factors are still associated with non-vaccine-type IPD risk, additional reductions in disparities should be expected with new, higher valency conjugate vaccines. [ABSTRACT FROM AUTHOR]

Background: A U.S. case-control study (2010-2014) demonstrated vaccine effectiveness (VE) for ≥ 1 dose of the thirteen-valent pneumococcal conjugate vaccine (PCV13) against vaccine-type (VT) invasive pneumococcal disease (IPD) at 86 %; however, it lacked statistical power to examine VE by number of doses and against individual serotypes., Methods: We used the indirect cohort method to estimate PCV13 VE against VT-IPD among children aged < 5 years in the United States from May 1, 2010 through December 31, 2019 using cases from CDC's Active Bacterial Core surveillance, including cases enrolled in a matched case-control study (2010-2014). Cases and controls were defined as individuals with VT-IPD and non-PCV13-type-IPD (NVT-IPD), respectively. We estimated absolute VE using the adjusted odds ratio of prior PCV13 receipt (1-aOR x 100 %)., Results: Among 1,161 IPD cases, 223 (19.2 %) were VT cases and 938 (80.8 %) were NVT controls. Of those, 108 cases (48.4 %; 108/223) and 600 controls (64.0 %; 600/938) had received > 3 PCV13 doses; 23 cases (17.6 %) and 15 controls (2.4 %) had received no PCV doses. VE ≥ 3 PCV13 doses against VT-IPD was 90.2 % (95 % Confidence Interval75.4-96.1 %), respectively. Among the most commonly circulating VT-IPD serotypes, VE of ≥ 3 PCV13 doses was 86.8 % (73.7-93.3 %), 50.2 % (28.4-80.5 %), and 93.8 % (69.8-98.8 %) against serotypes 19A, 3, and 19F, respectively., Conclusions: At least three doses of PCV13 continue to be effective in preventing VT-IPD among children aged < 5 years in the US. PCV13 was protective against serotypes 19A and 19F IPD; protection against serotype 3 IPD did not reach statistical significance., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Lee Harrison provides service on advisory boards (Pfizer, Sanofi, GSK) and a DSMB (Merck); while LH does not receive any fees for this work he is reimbursed for occasional travel. Tamara Pilishvili reports a relationship with GSK that includes: employment. During data collection, analysis, and write-up, TP was employed by CDC. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.]., (Copyright © 2024. Published by Elsevier Ltd.)

Objectives: Pediatric COVID-19 vaccine hesitancy and uptake is not well understood. Among parents of a prospective cohort of children aged 6 months-17 years, we assessed COVID-19 vaccine knowledge, attitudes, and practices (KAP), and uptake over 15 months., Methods: The PROTECT study collected sociodemographic characteristics of children at enrollment and COVID-19 vaccination data and parental KAPs quarterly. Univariable and multivariable logistic regression models were used to test the effect of KAPs on vaccine uptake; McNemar's test for paired samples was used to evaluate KAP change over time., Results: A total of 2,837 children were enrolled, with more than half (61 %) vaccinated by October 2022. Positive parental beliefs about vaccine safety and effectiveness strongly predicted vaccine uptake among children aged 5-11 years (aOR 13.1, 95 % CI 8.5-20.4 and aOR 6.4, 95 % CI 4.3-9.6, respectively) and children aged 12+ years (aOR 7.0, 95 % CI 3.8-13.0 and aOR 8.9, 95 % CI 4.4-18.0). Compared to enrollment, at follow-up parents (of vaccinated and unvaccinated children) reported higher self-assessed vaccine knowledge, but more negative beliefs towards vaccine safety, effectiveness, and trust in government. Parents unlikely to vaccinate their children at enrollment reported more positive beliefs on vaccine knowledge, safety, and effectiveness at follow-up., Conclusion: The PROTECT cohort allows for an examination of factors driving vaccine uptake and how beliefs about COVID-19 and the COVID-19 vaccines change over time. Findings of the current analysis suggest that these beliefs change over time and policies aiming to increase vaccine uptake should focus on vaccine safety and effectiveness., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Kurt T. Hegmann, MD serves as the editor-in-chief of the American College of Occupational and Environmental Medicine Guidelines; and Manjusha Gaglani, MD serves on the Texas Pediatric Society and Texas Chapter of the American Academy of Pediatrics. The other authors have no conflicts of interest to disclose., (Copyright © 2024 Abt Global LLC. Published by Elsevier Ltd.. All rights reserved.)

Pneumococcal conjugate vaccines (PCVs) prevent nasopharyngeal colonization with vaccine serotypes of Streptococcus pneumoniae, leading to reduced transmission of pneumococci and stronger population-level impact of PCVs. In 2017 we conducted a cross-sectional pneumococcal carriage study in Indonesia among children aged <5 years before 13-valent PCV (PCV13) introduction. Nasopharyngeal swabs were collected during visits to community integrated health service posts at one peri-urban and one rural study site. Specimens were analyzed by culture, and isolates were serotyped using sequential multiplex polymerase chain and Quellung reaction. Antibiotic susceptibility was performed by broth microdilution method. We enrolled 1,007 children in Gunungkidul District, Yogyakarta (peri-urban) and 815 in Southwest Sumba, East Nusa Tenggara (rural). Pneumococcal carriage prevalence was 30.9% in Gunungkidul and 87.6% in Southwest Sumba (combined: 56.3%). PCV13 serotypes (VT) carriage was 15.0% in Gunungkidul and 52.6% in Southwest Sumba (combined: 31.8%). Among pneumococcal isolates identified, the most common VT were 6B (16.4%), 19F (15.8%), and 3 (4.6%) in Gunungkidul (N = 323) and 6B (17.6%), 19F (11.0%), and 23F (9.3%) in Southwest Sumba (N = 784). Factors associated with pneumococcal carriage were age (1-2 years adjusted odds ratio (aOR) 1.9, 95% CI 1.4-2.5; 3-4 years aOR 1.5, 95% CI 1.1-2.1; reference <1 year), other children <5 years old in the household (aOR 1.5, 95% CI 1.1-2.0), and presence of ≥1 respiratory illness symptom (aOR 1.8, 95% CI 1.4-2.2). Overall, 61.5% of the pneumococcal isolates were non-susceptible to ≥1 antibiotic class and 13.2% were multi-drug non-susceptible (MDNS) (non-susceptible to ≥3 classes of antibiotics). Among 602 VT isolates, 73.9% were non-susceptible and 19.9% were MDNS. These findings are critical to establish a pre-PCV13 carriage prevalence and demonstrate the complexity in evaluating the impact of PCV13 introduction in Indonesia given the wide variability in the carriage prevalence as shown by the two study sites., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Background: SARS-CoV-2 Omicron variants have the potential to impact vaccine effectiveness and duration of vaccine-derived immunity. We analyzed U.S. multi-jurisdictional COVID-19 vaccine breakthrough surveillance data to examine potential waning of protection against SARS-CoV-2 infection for the Pfizer-BioNTech (BNT162b) primary vaccination series by age., Methods: Weekly numbers of SARS-CoV-2 infections during January 16, 2022-May 28, 2022 were analyzed by age group from 22 U.S. jurisdictions that routinely linked COVID-19 case surveillance and immunization data. A life table approach incorporating line-listed and aggregated COVID-19 case datasets with vaccine administration and U.S. Census data was used to estimate hazard rates of SARS-CoV-2 infections, hazard rate ratios (HRR) and percent reductions in hazard rate comparing unvaccinated people to people vaccinated with a Pfizer-BioNTech primary series only, by age group and time since vaccination., Results: The percent reduction in hazard rates for persons 2 weeks after vaccination with a Pfizer-BioNTech primary series compared with unvaccinated persons was lowest among children aged 5-11 years at 35.5% (95% CI: 33.3%, 37.6%) compared to the older age groups, which ranged from 68.7%-89.6%. By 19 weeks after vaccination, all age groups showed decreases in the percent reduction in the hazard rates compared with unvaccinated people; with the largest declines observed among those aged 5-11 and 12-17 years and more modest declines observed among those 18 years and older., Conclusions: The decline in vaccine protection against SARS-CoV-2 infection observed in this study is consistent with other studies and demonstrates that national case surveillance data were useful for assessing early signals in age-specific waning of vaccine protection during the initial period of SARS-CoV-2 Omicron variant predominance. The potential for waning immunity during the Omicron period emphasizes the importance of continued monitoring and consideration of optimal timing and provision of booster doses in the future., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Background: Protection against symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (coronavirus disease 2019 [COVID-19]) can limit transmission and the risk of post-COVID conditions, and is particularly important among healthcare personnel. However, lower vaccine effectiveness (VE) has been reported since predominance of the Omicron SARS-CoV-2 variant., Methods: We evaluated the VE of a monovalent messenger RNA (mRNA) booster dose against COVID-19 from October 2021 to June 2022 among US healthcare personnel. After matching case-participants with COVID-19 to control-participants by 2-week period and site, we used conditional logistic regression to estimate the VE of a booster dose compared with completing only 2 mRNA doses >150 days previously, adjusted for multiple covariates., Results: Among 3279 case-participants and 3998 control-participants who had completed 2 mRNA doses, we estimated that the VE of a booster dose against COVID-19 declined from 86% (95% confidence interval, 81%-90%) during Delta predominance to 65% (58%-70%) during Omicron predominance. During Omicron predominance, VE declined from 73% (95% confidence interval, 67%-79%) 14-60 days after the booster dose, to 32% (4%-52%) ≥120 days after a booster dose. We found that VE was similar by age group, presence of underlying health conditions, and pregnancy status on the test date, as well as among immunocompromised participants., Conclusions: A booster dose conferred substantial protection against COVID-19 among healthcare personnel. However, VE was lower during Omicron predominance, and waning effectiveness was observed 4 months after booster dose receipt during this period. Our findings support recommendations to stay up to date on recommended doses of COVID-19 vaccines for all those eligible., Competing Interests: Potential conflicts of interest. M. B. owned stock in Moderna from November 2022 to April 2023, as part of portfolio managed by Parametric Investments Portfolio. All other authors report no potential conflicts., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2023.)

Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Katherine A. Poehling reports institutional support from Safe Sleep for All Newborns, Love Out Loud Early Childhood Fellow, Intimate Partner Violence Collaborative Project, Because You Matter: Conversations You Want about COVID-19, text messaging follow-up for patients who missed well-child visits, and Reimagining Health and Wellness by Mothers for Our Babies, Families, and Communities. No other potential conflicts of interest were disclosed.

Background: Data on antibody kinetics are limited among individuals previously infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). From a cohort of healthcare personnel and other frontline workers in 6 US states, we assessed antibody waning after messenger RNA (mRNA) dose 2 and response to dose 3 according to SARS-CoV-2 infection history., Methods: Participants submitted sera every 3 months, after SARS-CoV-2 infection, and after each mRNA vaccine dose. Sera were tested for antibodies and reported as area under the serial dilution curve (AUC). Changes in AUC values over time were compared using a linear mixed model., Results: Analysis included 388 participants who received dose 3 by November 2021. There were 3 comparison groups: vaccine only with no known prior SARS-CoV-2 infection (n = 224); infection prior to dose 1 (n = 123); and infection after dose 2 and before dose 3 (n = 41). The interval from dose 2 and dose 3 was approximately 8 months. After dose 3, antibody levels rose 2.5-fold (95% confidence interval [CI] = 2.2-3.0) in group 2 and 2.9-fold (95% CI = 2.6-3.3) in group 1. Those infected within 90 days before dose 3 (and median 233 days [interquartile range, 213-246] after dose 2) did not increase significantly after dose 3., Conclusions: A third dose of mRNA vaccine typically elicited a robust humoral immune response among those with primary vaccination regardless of SARS-CoV-2 infection >3 months prior to boosting. Those with infection <3 months prior to boosting did not have a significant increase in antibody concentrations in response to a booster., Competing Interests: Potential conflicts of interest. A. L. N. reports research funding from Pfizer and Vir Biotechnology for unrelated studies. A. J. C.-M. reports Federal Emergency Management Agency grants (EMW-2019-FP-00526, EMW-2019-FP-00517, and EMW-2017-FP-00860) and State of Florida Appropriation 2369A and 2369A. M. G. reports grants or contracts unrelated to this work from the CDC–Abt Associates, CDC, CDC–VUMC, CDC–Westat and a role as co-chair of the Infectious Diseases and Immunization Committee, Texas Pediatric Society, Texas Chapter of the American Academy of Pediatrics. A. A. L. reports grants or contracts from Mercy C.A.R.E.S., National Heart Lung and Blood Institute, and the US Environmental Protection Agency and a leadership or fiduciary role with the Arizona Asthma Coalition. R. S. and J. L. U. report patents planned, issued, or pending (serological assays for SARS-CoV-2). All other authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Small sample sizes have limited prior studies' ability to capture severe COVID-19 outcomes, especially among Ad26.COV2.S vaccine recipients. This study of 18.9 million adults aged ≥18 years assessed relative vaccine effectiveness (rVE) in three recipient cohorts: (1) primary Ad26.COV2.S vaccine and Ad26.COV2.S booster (2 Ad26.COV2.S), (2) primary Ad26.COV2.S vaccine and mRNA booster (Ad26.COV2.S+mRNA), (3) two doses of primary mRNA vaccine and mRNA booster (3 mRNA)., Methods: We analyzed two de-identified datasets linked using privacy-preserving record linkage (PPRL): insurance claims and retail pharmacy COVID-19 vaccination data. We assessed the presence of COVID-19 diagnosis during January 1-March 31, 2022 in: (1) any claim, (2) outpatient claim, (3) emergency department (ED) claim, (4) inpatient claim, and (5) inpatient claim with intensive care unit (ICU) admission. rVE for each outcome comparing three recipient cohorts (reference: two Ad26.COV2.S doses) was estimated from adjusted Cox proportional hazards models., Results: Compared with two Ad26.COV2.S doses, Ad26.COV2.S+mRNA and three mRNA doses were more effective against all COVID-19 outcomes, including 57% (95% CI: 52-62) and 62% (95% CI: 58-65) rVE against an ED visit; 44% (95% CI: 34-52) and 54% (95% CI: 48-59) rVE against hospitalization; and 48% (95% CI: 22-66) and 66% (95% CI: 53-75) rVE against ICU admission, respectively., Conclusions: This study demonstrated that Ad26.COV2.S + mRNA doses were as good as three doses of mRNA, and better than two doses of Ad26.COV2.S. Vaccination continues to be an important preventive measure for reducing the public health impact of COVID-19., Competing Interests: Potential conflicts of interest . The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2023.)

New pneumococcal conjugate vaccines (PCVs), 15- and 20-valent (PCV15 and PCV20), have been licensed for use among U.S. adults based on safety and immunogenicity data compared with the previously recommended 13-valent PCV (PCV13) and 23-valent pneumococcal polysaccharide vaccines (PPSV23). We conducted a systematic review of the literature on PCV13 and PPSV23 efficacy (randomized controlled trials [RCTs]) or effectiveness (observational studies) against vaccine type (PCV13 type or PPSV23 type, respectively), invasive pneumococcal disease (IPD), and pneumococcal pneumonia (PP) in adults. We utilized the search strategy from a previous systematic review of the literature published during the period from January 2016 to April 2019, and updated the search through March 2022. The certainty of evidence was assessed using the Cochrane risk-of-bias 2.0 tool and the Newcastle-Ottawa scale. When feasible, meta-analyses were conducted. Of the 5085 titles identified, 19 studies were included. One RCT reported PCV13 efficacy of 75% (PCV13-type IPD) and 45% (PCV13-type PP). Three studies each reported PCV13 effectiveness against PCV13-type IPD (range 47% to 68%) and against PCV13-type PP (range 38% to 68%). The pooled PPSV23 effectiveness was 45% (95% CI: 37%, 51%) against PPSV23-type IPD (nine studies) and 18% (95% CI: -4%, 35%) against PPSV23-type PP (five studies). Despite the heterogeneity across studies, our findings suggest that PCV13 and PPSV23 protect against VT-IPD and VT-PP in adults.

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) BA.2/BA.2.12.1 and BA.4/BA.5 subvariants have mutations associated with increased capacity to evade immunity when compared with prior variants. We evaluated mRNA monovalent booster dose effectiveness among persons ≥5 years old during BA.2/BA.2.12.1 and BA.4/BA.5 predominance., Methods: A test-negative, case-control analysis included data from 12 148 pharmacy SARS-CoV-2 testing sites nationwide for persons aged ≥5 years with ≥1 coronavirus disease-2019 (COVID-19)-like symptoms and a SARS-CoV-2 nucleic acid amplification test from April 2 to August 31, 2022. Relative vaccine effectiveness (rVE) was estimated comparing 3 doses of COVID-19 mRNA monovalent vaccine to 2 doses; for tests among persons ≥50 years, rVE estimates also compared 4 doses to 3 doses (≥4 months since third dose)., Results: A total of 760 986 test-positive cases and 817 876 test-negative controls were included. Among individuals ≥12 years, rVE of 3 versus 2 doses ranged by age group from 45% to 74% at 1-month post vaccination and waned to 0% by 5-7 months post vaccination during the BA.4/BA.5 period.Adults aged ≥50 years (fourth dose eligible) who received 4 doses were less likely to have symptomatic SARS-CoV-2 infection compared with those with 3 doses; this rVE remained >0% through at least 3 months since last dose. For those aged ≥65 years, rVE of 4 versus 3 doses 1-month post vaccination was higher during BA.2/BA.2.12.1 (rVE = 49%; 95% confidence interval [CI], 43%-53%) than BA.4/BA.5 (rVE = 40%; 95% CI, 36%-44%). In 50- to 64-year-olds, rVE estimates were similar., Conclusions: Monovalent mRNA booster doses provided additional protection against symptomatic SARS-CoV-2 infection during BA.2/BA.2.12.1 and BA.4/BA.5 subvariant circulation, but protection waned over time., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2023.)

Background: Descriptions of changes in invasive bacterial disease (IBD) epidemiology during the coronavirus disease 2019 (COVID-19) pandemic in the United States are limited., Methods: We investigated changes in the incidence of IBD due to Streptococcus pneumoniae, Haemophilus influenzae, group A Streptococcus (GAS), and group B Streptococcus (GBS). We defined the COVID-19 pandemic period as 1 March to 31 December 2020. We compared observed IBD incidences during the pandemic to expected incidences, consistent with January 2014 to February 2020 trends. We conducted secondary analysis of a health care database to assess changes in testing by blood and cerebrospinal fluid (CSF) culture during the pandemic., Results: Compared with expected incidences, the observed incidences of IBD due to S. pneumoniae, H. influenzae, GAS, and GBS were 58%, 60%, 28%, and 12% lower during the pandemic period of 2020, respectively. Declines from expected incidences corresponded closely with implementation of COVID-19-associated nonpharmaceutical interventions (NPIs). Significant declines were observed across all age and race groups, and surveillance sites for S. pneumoniae and H. influenzae. Blood and CSF culture testing rates during the pandemic were comparable to previous years., Conclusions: NPIs likely contributed to the decline in IBD incidence in the United States in 2020; observed declines were unlikely to be driven by reductions in testing., Competing Interests: Presented in part: 12th International Symposium on Pneumococci and Pneumococcal Diseases, Toronto, Canada, 19-23 June., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2023.)

In a cohort of essential workers in the United States previously infected with SARS-CoV-2, risk factors for reinfection included being unvaccinated, infrequent mask use, time since first infection, and being non-Hispanic Black. Protecting workers from reinfection requires a multipronged approach including up-to-date vaccination, mask use as recommended, and reduction in underlying health disparities.

On June 18, 2022, the Advisory Committee on Immunization Practices (ACIP) issued interim recommendations for use of the 2-dose monovalent Moderna COVID-19 vaccine as a primary series for children aged 6 months-5 years* and the 3-dose monovalent Pfizer-BioNTech COVID-19 vaccine as a primary series for children aged 6 months-4 years, † based on safety, immunobridging, and limited efficacy data from clinical trials (1-3). Monovalent mRNA vaccine effectiveness (VE) against symptomatic SARS-CoV-2 infection was evaluated using the Increasing Community Access to Testing (ICATT) program, which provides SARS-CoV-2 testing to persons aged ≥3 years at pharmacy and community-based testing sites nationwide § (4,5). Among children aged 3-5 years with one or more COVID-19-like illness symptoms ¶ for whom a nucleic acid amplification test (NAAT) was performed during August 1, 2022-February 5, 2023, VE of 2 monovalent Moderna doses (complete primary series) against symptomatic infection was 60% (95% CI = 49% to 68%) 2 weeks-2 months after receipt of the second dose and 36% (95% CI = 15% to 52%) 3-4 months after receipt of the second dose. Among symptomatic children aged 3-4 years with NAATs performed during September 19, 2022-February 5, 2023, VE of 3 monovalent Pfizer-BioNTech doses (complete primary series) against symptomatic infection was 31% (95% CI = 7% to 49%) 2 weeks-4 months after receipt of the third dose; statistical power was not sufficient to estimate VE stratified by time since receipt of the third dose. Complete monovalent Moderna and Pfizer-BioNTech primary series vaccination provides protection for children aged 3-5 and 3-4 years, respectively, against symptomatic infection for at least the first 4 months after vaccination. CDC expanded recommendations for use of updated bivalent vaccines to children aged ≥6 months on December 9, 2022 (6), which might provide increased protection against currently circulating SARS-CoV-2 variants (7,8). Children should stay up to date with recommended COVID-19 vaccines, including completing the primary series; those who are eligible should receive a bivalent vaccine dose., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

On September 1, 2022, CDC recommended an updated (bivalent) COVID-19 vaccine booster to help restore waning protection conferred by previous vaccination and broaden protection against emerging variants for persons aged ≥12 years (subsequently extended to persons aged ≥6 months).* To assess the impact of original (monovalent) COVID-19 vaccines and bivalent boosters, case and mortality rate ratios (RRs) were estimated comparing unvaccinated and vaccinated persons aged ≥12 years by overall receipt of and by time since booster vaccination (monovalent or bivalent) during Delta variant and Omicron sublineage (BA.1, BA.2, early BA.4/BA.5, and late BA.4/BA.5) predominance. † During the late BA.4/BA.5 period, unvaccinated persons had higher COVID-19 mortality and infection rates than persons receiving bivalent doses (mortality RR = 14.1 and infection RR = 2.8) and to a lesser extent persons vaccinated with only monovalent doses (mortality RR = 5.4 and infection RR = 2.5). Among older adults, mortality rates among unvaccinated persons were significantly higher than among those who had received a bivalent booster (65-79 years; RR = 23.7 and ≥80 years; 10.3) or a monovalent booster (65-79 years; 8.3 and ≥80 years; 4.2). In a second analysis stratified by time since booster vaccination, there was a progressive decline from the Delta period (RR = 50.7) to the early BA.4/BA.5 period (7.4) in relative COVID-19 mortality rates among unvaccinated persons compared with persons receiving who had received a monovalent booster within 2 weeks-2 months. During the early BA.4/BA.5 period, declines in relative mortality rates were observed at 6-8 (RR = 4.6), 9-11 (4.5), and ≥12 (2.5) months after receiving a monovalent booster. In contrast, bivalent boosters received during the preceding 2 weeks-2 months improved protection against death (RR = 15.2) during the late BA.4/BA.5 period. In both analyses, when compared with unvaccinated persons, persons who had received bivalent boosters were provided additional protection against death over monovalent doses or monovalent boosters. Restored protection was highest in older adults. All persons should stay up to date with COVID-19 vaccination, including receipt of a bivalent booster by eligible persons, to reduce the risk for severe COVID-19., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Kathryn A. Turner reports an uncompensated position as the secretary/treasurer of the Board of the Council of State and Territorial Epidemiologists. No other potential conflicts of interest were disclosed.