Effectiveness of Bivalent mRNA COVID-19 Vaccines in Preventing SARS-CoV-2 Infection in Children and Adolescents Aged 5 to 17 Years

Abstract

ImportanceBivalent mRNA COVID-19 vaccines were recommended in the US for children and adolescents aged 12 years or older on September 1, 2022, and for children aged 5 to 11 years on October 12, 2022; however, data demonstrating the effectiveness of bivalent COVID-19 vaccines are limited.ObjectiveTo assess the effectiveness of bivalent COVID-19 vaccines against SARS-CoV-2 infection and symptomatic COVID-19 among children and adolescents.Design, Setting, and ParticipantsData for the period September 4, 2022, to January 31, 2023, were combined from 3 prospective US cohort studies (6 sites total) and used to estimate COVID-19 vaccine effectiveness among children and adolescents aged 5 to 17 years. A total of 2959 participants completed periodic surveys (demographics, household characteristics, chronic medical conditions, and COVID-19 symptoms) and submitted weekly self-collected nasal swabs (irrespective of symptoms); participants submitted additional nasal swabs at the onset of any symptoms.ExposureVaccination status was captured from the periodic surveys and supplemented with data from state immunization information systems and electronic medical records.Main Outcome and MeasuresRespiratory swabs were tested for the presence of the SARS-CoV-2 virus using reverse transcriptase–polymerase chain reaction. SARS-CoV-2 infection was defined as a positive test regardless of symptoms. Symptomatic COVID-19 was defined as a positive test and 2 or more COVID-19 symptoms within 7 days of specimen collection. Cox proportional hazards models were used to estimate hazard ratios for SARS-CoV-2 infection and symptomatic COVID-19 among participants who received a bivalent COVID-19 vaccine dose vs participants who received no vaccine or monovalent vaccine doses only. Models were adjusted for age, sex, race, ethnicity, underlying health conditions, prior SARS-CoV-2 infection status, geographic site, proportion of circulating variants by site, and local virus prevalence.ResultsOf the 2959 participants (47.8% were female; median age, 10.6 years [IQR, 8.0-13.2 years]; 64.6% were non-Hispanic White) included in this analysis, 25.4% received a bivalent COVID-19 vaccine dose. During the study period, 426 participants (14.4%) had laboratory-confirmed SARS-CoV-2 infection. Among these 426 participants, 184 (43.2%) had symptomatic COVID-19, 383 (89.9%) were not vaccinated or had received only monovalent COVID-19 vaccine doses (1.38 SARS-CoV-2 infections per 1000 person-days), and 43 (10.1%) had received a bivalent COVID-19 vaccine dose (0.84 SARS-CoV-2 infections per 1000 person-days). Bivalent vaccine effectiveness against SARS-CoV-2 infection was 54.0% (95% CI, 36.6%-69.1%) and vaccine effectiveness against symptomatic COVID-19 was 49.4% (95% CI, 22.2%-70.7%). The median observation time after vaccination was 276 days (IQR, 142-350 days) for participants who received only monovalent COVID-19 vaccine doses vs 50 days (IQR, 27-74 days) for those who received a bivalent COVID-19 vaccine dose.Conclusion and RelevanceThe bivalent COVID-19 vaccines protected children and adolescents against SARS-CoV-2 infection and symptomatic COVID-19. These data demonstrate the benefit of COVID-19 vaccine in children and adolescents. All eligible children and adolescents should remain up to date with recommended COVID-19 vaccinations.

Durability of Original Monovalent mRNA Vaccine Effectiveness Against COVID-19 Omicron–Associated Hospitalization in Children and Adolescents — United States, 2021–2023

“…In a separate U.S. study of children and adolescents aged 5–15 years, VE against symptomatic SARS-CoV-2 infections was reported to wane in the months after a second dose, with improved VE observed after receipt of a booster dose ( 4 ). Effectiveness of bivalent vaccine formulations against pediatric hospitalizations was not estimable in this investigation; however, two recent studies report that receipt of a bivalent vaccine was associated with higher VE against symptomatic pediatric infections ( 6 ) and COVID-19–related hospitalizations in immunocompetent adults ( 7 ).…”

The evolving epidemiology of SARS-CoV-2

“…Of the 426 infections discovered, 56.8% were asymptomatic, and symptomatic infections were mainly reported among those either not vaccinated, or who had only received the original monovalent vaccine. 22 Recent research 23 has also shown that viral load rises later, on average, during Omicron infections compared with earlier in the pandemic where the highest viral load in throat swabs was reported at the time of symptom onset, and the inferred infectiousness peaked on or before symptom onset. 24 The viral load in Omicron infections was found to most commonly peak on the third or fourth day after symptoms developed.…”