Children and adolescents ages 5-17 who received a bivalent COVID-19 mRNA vaccine were less likely to become infected with SARS-CoV-2 compared with those who were unvaccinated or received only the monovalent COVID-19 vaccine, according to new data published February 6 in JAMA.
“All eligible children and adolescents should remain up to date with recommended COVID-19 vaccinations,” wrote the authors, led by Leora R. Feldstein, PhD, with the US Centers for Disease Control and Prevention (CDC) in Atlanta.
By the end of 2023, at least 911 youths ages 5-17 had died from COVID-related causes.
Researchers found that compared with participants who did not receive the COVID-19 vaccine or got monovalent-only doses 180 days or more before, the adjusted vaccine effectiveness of a bivalent COVID-19 vaccine dose against SARS-CoV-2 infection was 51.3% (95% confidence interval [CI], 23.6%-71.9%) 7-60 days after vaccination. Relative effectiveness was 62.4% (95% CI, 38.5%-81.1%) 61-150 days after vaccination. The researchers said the confidence intervals were wide because of the small sample size.
The information can help inform public health strategies, the authors noted, especially as new variants emerge.
Bivalent Dose Recommended in Fall of 2022
Bivalent mRNA COVID vaccines were recommended in the United States for children and adolescents ages 12 years or older on Sept. 1, 2022, and for children ages 5-11 on Oct. 12, 2022, when Omicron BA.4/5 types were the predominant circulating variant.
The study included 2,959 participants who completed periodic surveys (answering questions on demographics, household details, chronic medical conditions, and COVID-19 symptoms) and submitted weekly self-collected nasal swabs (whether or not they had symptoms). Those in the study submitted additional nasal swabs if they developed any symptoms.
Median adherence to weekly upper respiratory specimen swabbing was high throughout the study period at 93.8%.
Data from Sept. 4, 2022, to Jan. 31, 2023, were combined from three prospective US cohort studies at six sites. In addition to the surveys, researchers used information from state immunization information systems and electronic medical records.
Most of the Infected Were Unvaccinated or Had Monovalent Vax
Of the 426 participants (14.4% of the combined cohorts) infected with SARS-CoV-2, 383 (89.9%) were either unvaccinated or received monovalent vaccine doses only.
Calculations were adjusted for age, sex, race, ethnicity, health conditions, prior SARS-CoV-2 infections, geographic location, proportion of circulating variants by site, and local virus prevalence.
Participants living in Oregon, for example, had the highest uptake of bivalent COVID-19 vaccine (56.2%), whereas those in Texas had the lowest (2.4%). Participants reporting Hispanic ethnicity had lower bivalent uptake (17.1%) compared with non-Hispanic participants of all races (27.1%).
Of the 2,207 participants who did not receive a bivalent dose, 24.2% were unvaccinated and 1,672 (75.8%) received at least 1 monovalent dose.
The researchers said they saw no sign of waning effectiveness 61-150 days (the limit for this analysis) after receipt of the bivalent COVID-19 vaccine.
They wrote that continuation of the cohorts will allow study of waning patterns, which could help inform vaccine recommendations.
Among the limitations of the study are that testing methods and the COVID-19 symptoms surveyed varied among the three cohorts, so there may be some differences in defining infection or symptomatic COVID. In addition, the researchers were not able to account for the social vulnerability index and immunocompromised status, which could have affected vaccine uptake and risk of SARS-CoV-2 infection.
This study was supported by the National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, and by the National Institute of Allergy and Infectious Diseases. Coauthor Dr. Caban-Martinez reported grants from the Florida Firefighter Cancer Initiative and the Florida Department of Health. Coauthors Dr. Chu, Dr. Englund, Dr. Martin, and Dr. Monto reported receiving personal fees or grants from multiple pharmaceutical companies. Dr. Hegmann reported being the editor of the American College of Occupational and Environmental Medicine practice guidelines. Coauthor Dr. Gaglani reported serving as cochair of the infectious diseases and immunization committee and the respiratory syncytial virus task force lead for the Texas Pediatric Society and the Texas Chapter of the American Academy of Pediatrics. No other disclosures were reported.