Journal name: Journal of American Medical Association (JAMA)

Publishing date: May 13, 2022

Author: Vajeera Dorabawila et.al

The incidence and hospitalisations due to COVID-19 were lower in vaccinated adolescents and children compared to unvaccinated comparison groups. Vaccine effectiveness and efficacy have been found to decrease with the spread of the Omicron variant.

Why does this study matter?

The effectiveness of the COVID-19 vaccine among children and adolescents is still a topic of discussion. This study assesses the impact of vaccination on COVID-19 incidence and hospitalisation in these age groups after the emergence of the Omicron variant.

Study Design

Cases and hospitalisations were compared among fully vaccinated and unvaccinated youth in the age groups 5 to 11 and 12 to 17 using databases of 4 New York states. Cases were defined as those with positive nucleic acid amplification test or antigen test results.

For each age group cases and hospitalisations were considered for weekly cohorts of fully vaccinated and unvaccinated individuals of each age group from November 9, 2021, to January 30, 2022. Comparing vaccinated and unvaccinated rates, incidence rate ratios (IRR) were calculated within each age group.

Results and Conclusion

365502 children aged 5 to 11 years were fully vaccinated (mean [SD] age, 8.3 [2.0] years; 51% boys) and 997 554 were unvaccinated (mean [SD] age, 7.8 [2.0] years; 51% boys) as of January 30, 2022. 852 384 adolescents aged 12 to 17 years were fully vaccinated (mean [SD] age, 14.6 [1.6] years; 50% boys) and 208 145 were unvaccinated (mean [SD] age, 14.6 [1.7] years; 53% boys).

Among children aged 5 to 11 years, 140 680 cases of COVID-19 and 414 hospitalisations were observed. 154 555 cases and 671 hospitalisations were observed among adolescents aged 12 to 17 years.

Among adolescents, the unvaccinated vs vaccinated IRR against cases declined from 6.7 (95% CI, 6.2-7.2) the week of November 29 to 2.9 (95% CI, 2.8-3.0) the week of December 13 (Omicron 19% sequences) and further to 2.0 (95% CI, 1.9-2.2) by January 24 (Omicron >99% sequences).

Among children, the IRR was 3.1 (95% CI, 2.7-3.6) the week of December 13 and declined to 1.1 (95% CI, 1.1-1.2) by January 24. With an IRR of 1.9 (95% CI, 0.9-4.8) for children aged 5 to 11 years compared with 3.7 (95% CI, 2.1-6.5) for those aged 12 to 17 years, hospitalisations were higher in unvaccinated than fully vaccinated individuals by the week of January 24.

The chances of infection and hospitalisation were higher in unvaccinated than vaccinated children, although the risk declined with the spread of the omicron variant. The results of the study supplement the previously known reduced effectiveness of the vaccine for children and adolescents against newer SARS CoV-2 variants like Delta.

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