Evaluation of BNT162b2 Covid-19 Vaccine in Children Younger than 5 Years of Age.

BACKGROUND: Safe and effective vaccines against coronavirus disease 2019 (Covid-19) are urgently needed in young children. METHODS: We conducted a phase 1 dose-finding study and are conducting an ongoing phase 2-3 safety, immunogenicity, and efficacy trial of the BNT162b2 vaccine in healthy children 6 months to 11 years of age. We present results for children 6 months to less than 2 years of age and those 2 to 4 years of age through the data-cutoff dates (April 29, 2022, for safety and immunogenicity and June 17, 2022, for efficacy). In the phase 2-3 trial, participants were randomly assigned (in a 2:1 ratio) to receive two 3-µg doses of BNT162b2 or placebo. On the basis of preliminary immunogenicity results, a third 3-µg dose (≥8 weeks after dose 2) was administered starting in January 2022, which coincided with the emergence of the B.1.1.529 (omicron) variant. Immune responses at 1 month after doses 2 and 3 in children 6 months to less than 2 years of age and those 2 to 4 years of age were immunologically bridged to responses after dose 2 in persons 16 to 25 years of age who received 30 µg of BNT162b2 in the pivotal trial. RESULTS: During the phase 1 dose-finding study, two doses of BNT162b2 were administered 21 days apart to 16 children 6 months to less than 2 years of age (3-µg dose) and 48 children 2 to 4 years of age (3-µg or 10-µg dose). The 3-µg dose level was selected for the phase 2-3 trial; 1178 children 6 months to less than 2 years of age and 1835 children 2 to 4 years of age received BNT162b2, and 598 and 915, respectively, received placebo. Immunobridging success criteria for the geometric mean ratio and seroresponse at 1 month after dose 3 were met in both age groups. BNT162b2 reactogenicity events were mostly mild to moderate, with no grade 4 events. Low, similar incidences of fever were reported after receipt of BNT162b2 (7% among children 6 months to <2 years of age and 5% among those 2 to 4 years of age) and placebo (6 to 7% among children 6 months to <2 years of age and 4 to 5% among those 2 to 4 years of age). The observed overall vaccine efficacy against symptomatic Covid-19 in children 6 months to 4 years of age was 73.2% (95% confidence interval, 43.8 to 87.6) from 7 days after dose 3 (on the basis of 34 cases). CONCLUSIONS: A three-dose primary series of 3-µg BNT162b2 was safe, immunogenic, and efficacious in children 6 months to 4 years of age. (Funded by BioNTech and Pfizer; ClinicalTrials.gov number, NCT04816643.).

Evaluation of the BNT162b2 Covid-19 Vaccine in Children 5 to 11 Years of Age.

BACKGROUND: Safe, effective vaccines against coronavirus disease 2019 (Covid-19) are urgently needed in children younger than 12 years of age. METHODS: A phase 1, dose-finding study and an ongoing phase 2-3 randomized trial are being conducted to investigate the safety, immunogenicity, and efficacy of two doses of the BNT162b2 vaccine administered 21 days apart in children 6 months to 11 years of age. We present results for 5-to-11-year-old children. In the phase 2-3 trial, participants were randomly assigned in a 2:1 ratio to receive two doses of either the BNT162b2 vaccine at the dose level identified during the open-label phase 1 study or placebo. Immune responses 1 month after the second dose of BNT162b2 were immunologically bridged to those in 16-to-25-year-olds from the pivotal trial of two 30-µg doses of BNT162b2. Vaccine efficacy against Covid-19 at 7 days or more after the second dose was assessed. RESULTS: During the phase 1 study, a total of 48 children 5 to 11 years of age received 10 µg, 20 µg, or 30 µg of the BNT162b2 vaccine (16 children at each dose level). On the basis of reactogenicity and immunogenicity, a dose level of 10 µg was selected for further study. In the phase 2-3 trial, a total of 2268 children were randomly assigned to receive the BNT162b2 vaccine (1517 children) or placebo (751 children). At data cutoff, the median follow-up was 2.3 months. In the 5-to-11-year-olds, as in other age groups, the BNT162b2 vaccine had a favorable safety profile. No vaccine-related serious adverse events were noted. One month after the second dose, the geometric mean ratio of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing titers in 5-to-11-year-olds to those in 16-to-25-year-olds was 1.04 (95% confidence interval [CI], 0.93 to 1.18), a ratio meeting the prespecified immunogenicity success criterion (lower bound of two-sided 95% CI, >0.67; geometric mean ratio point estimate, ≥0.8). Covid-19 with onset 7 days or more after the second dose was reported in three recipients of the BNT162b2 vaccine and in 16 placebo recipients (vaccine efficacy, 90.7%; 95% CI, 67.7 to 98.3). CONCLUSIONS: A Covid-19 vaccination regimen consisting of two 10-µg doses of BNT162b2 administered 21 days apart was found to be safe, immunogenic, and efficacious in children 5 to 11 years of age. (Funded by BioNTech and Pfizer; ClinicalTrials.gov number, NCT04816643.).

Safety and Immunogenicity of an Andes Virus DNA Vaccine by Needle-Free Injection: A Randomized, Controlled Phase 1 Study.

BACKGROUND: Andes virus (ANDV), a rodent-borne hantavirus, causes hantavirus pulmonary syndrome (HPS). The safety and immunogenicity of a novel ANDV DNA vaccine was evaluated. METHODS: Phase 1, double-blind, dose-escalation trial randomly assigned 48 healthy adults to placebo or ANDV DNA vaccine delivered via needle-free jet injection. Cohorts 1 and 2 received 2 mg of DNA or placebo in a 3-dose (days 1, 29, 169) or 4-dose (days 1, 29, 57, 169) schedule, respectively. Cohorts 3 and 4 received 4 mg of DNA or placebo in the 3-dose and 4-dose schedule, respectively. Subjects were monitored for safety and neutralizing antibodies by pseudovirion neutralization assay (PsVNA50) and plaque reduction neutralization test (PRNT50). RESULTS: While 98% and 65% of subjects had at least 1 local or systemic solicited adverse event (AE), respectively, most AEs were mild or moderate; no related serious AEs were detected. Cohorts 2, 3, and 4 had higher seroconversion rates than cohort 1 and seropositivity of at least 80% by day 197, sustained through day 337. PsVNA50 geometric mean titers were highest for cohort 4 on and after day 197. CONCLUSIONS: This first-in-human candidate HPS vaccine trial demonstrated that an ANDV DNA vaccine was safe and induced a robust, durable immune response. Clinical Trials Registration. NCT03682107.

The Durability of Antibody Responses of Two Doses of High-Dose Relative to Two Doses of Standard-Dose Inactivated Influenza Vaccine in Pediatric Hematopoietic Cell Transplant Recipients: A Multi-Center Randomized Controlled Trial.

BACKGROUND: Our previous study established a 2-dose regimen of high-dose trivalent influenza vaccine (HD-TIV) to be immunogenically superior compared to a 2-dose regimen of standard-dose quadrivalent influenza vaccine (SD-QIV) in pediatric allogeneic hematopoietic cell transplant (HCT) recipients. However, the durability of immunogenicity and the role of time post-HCT at immunization as an effect modifier are unknown. METHODS: This phase II, multi-center, double-blinded, randomized controlled trial compared HD-TIV to SD-QIV in children 3-17 years old who were 3-35 months post-allogeneic HCT, with each formulation administered twice, 28-42 days apart. Hemagglutination inhibition (HAI) titers were measured at baseline, 28-42 days following each dose, and 138-222 days after the second dose. Using linear mixed effects models, we estimated adjusted geometric mean HAI titer ratios (aGMR: HD-TIV/SD-QIV) to influenza antigens. Early and late periods were defined as 3-5 and 6-35 months post-HCT, respectively. RESULTS: During 3 influenza seasons (2016-2019), 170 participants were randomized to receive HD-TIV (n = 85) or SD-QIV (n = 85). HAI titers maintained significant elevations above baseline for both vaccine formulations, although the relative immunogenic benefit of HD-TIV to SD-QIV waned during the study. A 2-dose series of HD-TIV administered late post-HCT was associated with higher GMTs compared to the early post-HCT period (late group: A/H1N1 aGMR = 2.16, 95% confidence interval [CI] = [1.14-4.08]; A/H3N2 aGMR = 3.20, 95% CI = [1.60-6.39]; B/Victoria aGMR = 1.91, 95% CI = [1.01-3.60]; early group: A/H1N1 aGMR = 1.03, 95% CI = [0.59-1.80]; A/H3N2 aGMR = 1.23, 95% CI = [0.68-2.25]; B/Victoria aGMR = 1.06, 95% CI = [0.56-2.03]). CONCLUSIONS: Two doses of HD-TIV were more immunogenic than SD-QIV, especially when administered ≥6 months post-HCT. Both groups maintained higher titers compared to baseline throughout the season. CLINICAL TRIALS REGISTRATION: NCT02860039.

Acute severe respiratory syndrome coronavirus-2 treatment overview for pediatrics.

PURPOSE OF REVIEW: The novel severe respiratory syndrome coronavirus-2 (SARS-CoV-2) virus has caused a world-wide pandemic with devastating effects. Fortunately, most children display only mild-to-moderate symptoms, but there are a subset that will have severe symptoms warranting treatment. This review evaluates the current evidence for antiviral and anti-inflammatory treatment of acute SARS-COV-2 infections, including coronavirus disease 2019 in pediatrics. RECENT FINDINGS: Treatment recommendations continue to evolve with emerging results from clinical trials. Initial therapies were tailored to repurposed medications, and have now transitioned toward more specific antiviral therapy. In addition to specific antiviral therapy, there is also support to modulate the immune system and reduce inflammatory damage seen in coronavirus disease 2019. Much of the data result from adult studies with subsequent extrapolation to pediatrics. SUMMARY: Recommended therapy will continue to adapt as results return from clinical trials. A continued commitment from the National Institutes of Health and research community to assist in determining optimal therapies for pediatric patients is essential. Until then, most recommendations will likely be informed from the results seen in adult populations.

A multicenter study to define the epidemiology and outcomes of Clostridioides difficile infection in pediatric hematopoietic cell and solid organ transplant recipients.

Hematopoietic cell transplant (HCT) and solid organ transplant (SOT) recipients are at increased risk for Clostridioides difficile infection (CDI). We conducted a multicenter retrospective study to describe the incidence of CDI in children transplanted between January 2010 and June 2013. Nested case-control substudies, matched 1:1 by transplant type, institution, patient age, and time of year (quartile) of transplant, identified CDI risk factors. Cohorts included 1496 HCT and 1090 SOT recipients. Among HCT recipients, 355 CDI episodes were diagnosed in 265 recipients (18.2%). Nested case-control study identified prior history of CDI (odds ratio [OR] 2.6, 95% confidence interval [CI] 1.5-4.7), proton pump inhibitors (PPIs; OR 2.1, 95% CI 1.3-3.4), and exposure to third- (OR 2.4, 95% CI 1.4-4.2) or fourth-generation (OR 2.1, 95% CI 1.2-3.7) cephalosporins as risk factors. Notably, fluoroquinolone exposure appeared protective (OR 0.6, 95% CI 0.3-0.9). Ninety-two episodes of CDI were diagnosed among 79 SOT recipients (7.3%), and exposure to PPIs (OR 2.4, 95% CI 1.1-5.4) and third-generation cephalosporin therapy (OR 3.9, 95% CI 1.4-10.5) were identified as risk factors. Strategies to decrease PPI use and changes in the class of prophylactic antibiotics may impact CDI incidence and warrant further study.

Evaluation of a change in cytomegalovirus prevention strategy following pediatric solid organ transplantation.

BACKGROUND: An optimal cytomegalovirus (CMV) prevention strategy following solid organ transplantation (SOT) remains uncertain. This study reports on the rates of CMV events following a change in a local prevention guideline involving increased surveillance, earlier transition to oral valganciclovir, and decreased CMV-immunoglobulin use. METHODS: A retrospective cohort study utilizing historical controls evaluated the rates of CMV invasive disease pre- and post-intervention among pediatric heart, liver, and kidney recipients. Outcomes were recorded for the 4 years pre- and post-intervention, 9/2009-10/2017. Logistic regression was used to estimate the risk of a CMV event. RESULTS: There was no difference in the rates of CMV invasive disease between the two study groups (P = 1). An increase in the detection of CMV events occurred (P = .04), predominantly asymptomatic CMV infection. This increase was independently associated with increased surveillance testing among high-risk heart and liver recipients, aOR 1.08 (1.06-1.12). Surprisingly, 28.9% of CMV events occurred during antiviral prophylaxis. CONCLUSIONS: Modification of the local CMV prevention guideline did not result in an increase in CMV invasive disease. CMV events occurred while on prophylaxis, highlighting a potential difference from adult solid organ transplant (SOT) and emphasizing the potential need for monitoring on prophylaxis in the pediatric population.

Variability of Pneumocystis jirovecii prophylaxis use among pediatric solid organ transplant providers.

Pneumocystis jirovecii pneumonia (PJP) prophylaxis after pediatric solid organ transplant (SOT) is routinely recommended, but practice varies. Online survey was sent in 2018 to 707 members of the International Pediatric Transplant Association. A total of 105 responded, representing 47 institutions in 18 countries consisting of transplant physicians (66%), transplant surgeons (19%), nurse practitioners (6%), infectious disease physicians (5%), or pharmacists (4%). PJP prophylaxis was reported by 88%, while 12% did not routinely give prophylaxis. The majority not using PJP prophylaxis performed renal transplants (67%) citing low incidence of PJP (62%). Trimethoprim/sulfamethoxazole was first-line agent (95%). PJP prophylaxis for 4-6 months was the most frequent duration following kidney (48%, 27/56), liver (42%, 13/31), and heart (40%, 10/25) transplant. Abdominal multivisceral providers equally gave 10-12 months (47%) or lifelong (47%); most lung transplant providers gave lifelong prophylaxis (85%). Across all organs, 21% provided lifetime prophylaxis. After completion of prophylaxis, 32% do not restart for any reason; majority of the rest would restart for treatment of acute graft rejection. 83% reported no PJP cases in the prior 12 months; 14% reporting 1-5 infections. Only 3% reported a case of PJP infection on prophylaxis; none in SOT. PJP prophylaxis is routinely provided to pediatric SOT patients though practice and duration vary by center and organ type. Durations of 4-6 months were most common for renal, liver, and heart transplant recipients, while 10-12 months or lifelong prophylaxis were commonly reported for abdominal multivisceral recipients and most lung transplant recipients are given lifelong prophylaxis.

Cytomegalovirus and Epstein-Barr virus infections among pediatric kidney transplant recipients at a center using universal Valganciclovir Prophylaxis.

BACKGROUND: CMV is associated with adverse effects in renal transplant recipients. The objective of this study was to characterize the incidence and timing of CMV and EBV infections in relation to valGCV prophylaxis in a pediatric renal transplant cohort. METHODS: Retrospective cohort of pediatric renal transplant patients given universal valGCV prophylaxis and universal viral surveillance was evaluated. Demographics, prophylaxis, acute rejection, and CMV and EBV infections were abstracted. RESULTS: A total of 92 pediatric renal allograft recipients, 2008-2013, were included. One or more viral infections developed in 77/92 (83.7%) of the patients. EBV was the most common in 62/92 (67%) patients, irrespective of valGCV (82% of episodes occurring on valGCV). CMV DNAemia occurred in 30/92 (33%) patients, 14 episodes (47%) occurring on valGCV. Incidence of breakthrough CMV on prophylaxis was 15% and was associated with persistent DNAemia (OR 7.8, CI:1.6-32.9, P < 0.02). CMV tissue-invasive disease was not seen. CMV syndrome occurred in 10% of the cohort, only in CMV D+ patients, and only one symptomatic breakthrough infection required treatment. Out of 92, 21 (23%) had simultaneous co-infections with 2-3 viruses. CONCLUSIONS: Viral infections in pediatric renal transplant recipients receiving universal valGCV prophylaxis were common. EBV infections were not reduced by valGCV prophylaxis, and nearly half of CMV infections occurred on valGCV. Symptomatic CMV infection while on prophylaxis was rare. valGCV prophylaxis may prevent symptomatic CMV infection but not EBV infection, and frequent CMV surveillance in pediatric renal transplant recipients on prophylaxis may not be necessary.

Durability of the hepatitis B vaccination in pediatric renal transplant recipients.

Since hepatitis B virus (HBV) vaccine implementation, HBV infection has significantly decreased. However, adult renal transplant recipients show a higher rate of seroreversion compared to the general population, leading to HBV infection risk. Data are limited in pediatric renal transplant recipients. Retrospective data were collected to determine the seroprotection and durability of HBV vaccination in pediatric renal transplant patients from 2004 to 2014. One hundred subjects were categorized based on pre- and post-transplant hepatitis B surface antibody (HBsAb). Pretransplant, 85 recipients (85%) had a positive HBsAb compared to 15 (15%) with negative HBsAb. In univariable analyses, other than age (P < .05) no significant differences existed pretransplant by demographics, pretransplantation dialysis, or number of vaccinations. Of the 85 pretransplantation responders, 53 (62%) remained HBsAb positive post-transplantation, 28 (32%) seroreverted, and 4 developed indeterminate titers. All seroreversions occurred within 5 years post-transplant. Receipt of a living donor organ had higher risk of reversion (P = .005). No significant differences were found in demographics, pretransplantation dialysis, vaccination number, or acute rejection. Despite vaccination, 15% of pediatric renal transplant candidates were seronegative, and an additional 32% lost seroprotection within 5 years post-transplantation leaving nearly half of transplant recipients at risk for HBV infection.

Epidemiology and outcomes of pretransplant methicillin-resistant Staphylococcus Aureus screening in pediatric solid organ transplant candidates.

MRSA infection following SOT is an important cause of morbidity and mortality, but epidemiology and risk factors for colonization prior to pediatric SOT remain unclear. A retrospective cohort of SOT patients ≤21 years of age from 2009 to 2014 was evaluated. Demographics, MRSA screens, timing of transplantation, and MRSA infection were abstracted. From 2013 to 2014, 130 SOT candidates were screened or had known prior MRSA infection. Seventeen patients (13%) were MRSA colonized. Liver transplant candidates were least likely to be colonized (OR 0.22, CI:0.06-0.81, P = .02); greatest risk of colonization was in lung (OR 18.7, CI:1.9-182.3, P = .03), abdominal multivisceral (OR 7.5, CI:1.5-38.6, P = .02), and cardiac patients with history of cardiothoracic surgery (OR 8.0, CI:1.7-36.0, P = .007). In univariable analysis, African American patients were more likely to be colonized (OR 7.1, CI:2.49-19.41, P = .0005). There were 3 early MRSA infections in screened patients, incidence of 3.9%; only one in a colonized patient. Thirteen percent of screened pediatric SOT candidates were MRSA colonized, with greatest risk in lung, multivisceral and cardiac patients with prior cardiothoracic surgery. Early MRSA infection occurred in 3.9% of transplanted patients. Cardiothoracic and multivisceral organ transplant candidates may benefit the most from targeted MRSA screening.

Fall 2023 ACIP Update on Meningococcal, RSV, COVID-19, and Other Pediatric Vaccines.

The Advisory Committee on Immunization Practices (ACIP), a group of medical and public health experts that provides advice to the Centers for Disease Control and Prevention, normally meets 3 times per year to develop US vaccine recommendations. The ACIP met October 25 to 26, 2023, to discuss meningococcal vaccines, mpox vaccines, respiratory syncytial virus (RSV) vaccines, influenza vaccines, coronavirus disease 2019 (COVID-19) vaccines, and the combined pediatric and adult immunization schedules for 2024. The ACIP also held special meetings on September 12 and September 22 to discuss COVID-19 2023-2024 vaccine recommendations and RSV immunization in pregnant women. This update summarizes the proceedings of these meetings that are most relevant to the pediatric population. Major updates for pediatric clinicians include recommendations for XBB monovalent COVID-19 immunization for the 2023-2024 respiratory season, the recently licensed pentavalent meningococcal conjugate vaccine and mpox vaccination in high-risk young adults, and discussion regarding the parallel strategies of protection against RSV disease in infants via maternal immunization during pregnancy or direct prophylaxis of infants with nirsevimab.

Disseminated Disease After Candidemia in Children and Young Adults: Epidemiology, Diagnostic Evaluation and Risk Factors.

BACKGROUND: Treatment of candidemia may be complicated by hematogenous dissemination. Limited data exist to guide decision-making regarding the evaluation for disseminated disease. We sought to describe the epidemiology of invasive disease after candidemia, report the diagnostic evaluations performed and identify risk factors for disseminated disease. METHODS: We performed a retrospective single-center study of candidemia from January 1, 2012 to December 31, 2022. Disseminated candidiasis was defined as radiologic findings consistent with end-organ disease, abnormal ophthalmologic exam or growth of Candida spp. from a sterile site after an episode of candidemia. A multilevel regression model was used to identify risk factors for dissemination. RESULTS: The cohort included 124 patients with 144 episodes of candidemia. Twelve patients died before an evaluation for dissemination occurred. Only 107/132 patients underwent evaluation for dissemination. Tests obtained included abdominal imaging (93/132), echocardiography (91/132), neuroimaging (45/132) and chest imaging (38/132). A retinal examination was performed in 90/132 patients. Overall, 27/107 patients (25%) had disseminated disease. Frequently identified sites of dissemination were lungs and abdominal organs. Regression modeling identified prematurity [adjusted odds ratio (aOR): 11.88; 95% confidence interval (CI): 1.72-81.90] and mitochondrial and genetic disease (aOR: 5.66; 95% CI: 1.06-30.17) as risk factors for disseminated candidiasis. Each additional day of candidemia increased the odds of dissemination (aOR: 1.36; 95% CI: 1.12-1.66). DISCUSSION: In a heterogeneous cohort of patients, disseminated candidiasis was common. Evaluation for disseminated disease was variable. Those with persistent candidemia had significantly increased risk of dissemination and should undergo a standardized evaluation for disseminated disease.

February 2024 ACIP Meeting Update: Meningococcal, RSV, COVID-19, and Other Vaccines.

The Advisory Committee on Immunization Practices, a group of medical and public health experts that provides advice to the Centers for Disease Control and Prevention, normally meets 3 times per year to develop US vaccine recommendations. The Advisory Committee on Immunization Practices met February 28 to 29, 2024, to discuss coronavirus disease 2019 vaccines, chikungunya vaccines, diphtheria-tetanus vaccine, influenza vaccines, polio vaccines, respiratory syncytial virus vaccines, meningococcal vaccines, pneumococcal vaccines, and Vaxelis (Diphtheria, Tetanus, Pertussis, Inactivated Poliovirus, Haemophilus influenzae b Conjugate, and Hepatitis B Vaccine). This update summarizes the proceedings of these meetings, with an emphasis on topics that are most relevant to the pediatric population. Major updates for pediatric clinicians include information about changes on influenza vaccine composition, meningococcal vaccination considerations, updated guidance for children with a contraindication to pertussis-containing vaccines, and recommendations of the world's first chikungunya vaccine for certain populations.

Immunophenotypic predictors of influenza vaccine immunogenicity in pediatric hematopoietic cell transplant recipients.

ABSTRACT: Pediatric hematopoietic cell transplant (HCT) recipients exhibit poor serologic responses to influenza vaccination early after transplant. To facilitate the optimization of influenza vaccination timing, we sought to identify B- and T-cell subpopulations associated with influenza vaccine immunogenicity in this population. We used mass cytometry to phenotype peripheral blood mononuclear cells collected from pediatric HCT recipients enrolled in a multicenter influenza vaccine trial comparing high- and standard-dose formulations over 3 influenza seasons (2016-2019). We fit linear regression models to estimate relationships between immune cell subpopulation numbers before vaccination and prevaccination to postvaccination geometric mean fold rises in antigen-specific (A/H3N2, A/H1N1, and B/Victoria) serum hemagglutination inhibition antibody titers (28-42 days, and ∼6 months after 2 doses). For cell subpopulations identified as predictive of a response to all 3 antigens, we conducted a sensitivity analysis including time after transplant as an additional covariate. Among 156 HCT recipients, we identified 33 distinct immune cell subpopulations; 7 significantly predicted responses to all 3 antigens 28 to 42 days after a 2-dose vaccine series, irrespective of vaccine dose. We also found evidence that baseline absolute numbers of naïve B cells, naïve CD4+ T cells, and circulating T follicular helper cells predicted peak and sustained vaccine-induced titers irrespective of dose or timing of posttransplant vaccine administration. In conclusion, several B- and T-cell subpopulations predicted influenza vaccine immunogenicity in pediatric HCT recipients. This study provides insights into the immune determinants of vaccine responses and may help guide the development of tailored vaccination strategies for this vulnerable population.

Bivalent Omicron BA.4/BA.5 BNT162b2 Vaccine in 6-Month- to <12-Year-Olds.

BACKGROUND: With the future epidemiology and evolution of SARS-CoV-2 uncertain, use of safe and effective COVID-19 vaccines in pediatric populations remains important. METHODS: We report data from two open-label substudies of an ongoing phase 1/2/3 master study (NCT05543616) investigating safety and immunogenicity of a variant-adapted bivalent COVID-19 vaccine encoding ancestral and Omicron BA.4/BA.5 spike proteins (bivalent BNT162b2). The open-label groups presented here evaluate dose 4 with bivalent BNT162b2 in 6-month-<12-year-olds who previously received three original (monovalent) BNT162b2 doses. In 6-month-<5-year-olds, primary immunogenicity objectives were to demonstrate superiority (neutralizing titer) and noninferiority (seroresponse rate) to Omicron BA.4/BA.5 and noninferiority (neutralizing titer and seroresponse rate) to SARS-CoV-2 ancestral strains in participants who received bivalent BNT162b2 dose 4 compared with a matched group who received three doses of original BNT162b2 in the pivotal pediatric study (NCT04816643). In 5-<12-year-olds, primary immunogenicity comparisons were descriptive. Reactogenicity and safety following vaccination were evaluated. RESULTS: In 6-month-<5-year-olds, dose 4 with bivalent BNT162b2 met predefined immunogenicity superiority and noninferiority criteria against Omicron BA.4/BA.5 and ancestral strains when compared with dose 3 of original BNT162b2. In 5-<12-year-olds, bivalent BNT162b2 induced robust Omicron BA.4/BA.5 and ancestral strain neutralizing titers comparable to dose 3 of original BNT162b2. The safety profile for dose 4 of bivalent BNT162b2 given as dose 4 was consistent with that of original BNT162b2 in 6 month-<12-year-olds. Reactogenicity events were generally mild-to-moderate. No adverse events led to discontinuation. CONCLUSIONS: These safety and immunogenicity data support a favorable benefit-risk profile for a variant-adapted BNT162b2 in children <12 years old.