1. Two doses of the Pfizer-BioNTech vaccine resulted in moderate protection against SARS-CoV-2 infection in children aged 5 to 11.
2. The Pfizer-BioNTech vaccine also provided moderate protection against symptomatic coronavirus disease 2019 (COVID-19) in children aged 5 to 11.
Evidence Rating Level: 1 (Excellent)
Study Rundown: The development of vaccinations to protect against COVID-19 has resulted in fewer and less severe infections. Though, the vaccine efficacy has been predominantly studied in adults. Children aged 5 to 11 are also susceptible to SARS-CoV-2 infection, though they are more likely to present with asymptomatic infection or milder symptoms as compared to older adults. However, the spread of the delta variant has increased the incidence of pediatric COVID-19-related hospitalizations in the United States. Moreover, the omicron variant, which has been the most recent dominant variant, has also been shown to infect children. The infectivity and severity of infection of the omicron variant and associated vaccine effectiveness against it have not been well evaluated in children. Thus, there is a gap in knowledge as to understanding whether the Pfizer-BioNTech vaccine confers protection against the omicron variant in children. Overall, this study found that the Pfizer-BioNTech vaccine showed moderate protection against COVID-19 infection and symptoms among children aged 5 to 11, during a period in which omicron was the prevalent variant. This study was limited by only being able to measure short-term effectiveness and the possibility of residual confounding variables, such as behavioral factors of wearing masks, were not assessed. Nevertheless, the study’s findings are significant as they demonstrate that the Pfizer-BioNTech confers moderate protection against COVID-19 in children ages 5 to 11.
In-Depth [retrospective cohort]: The present observational cohort study was conducted with data from Israel’s largest healthcare service provider. Patients between 5 to 11 years of age, had at least 12 months of continuous membership with the healthcare service provider, and had no previous PCR, serology, or antigen test that was positive for SARS-CoV-2 were eligible for the study. Patients who were homebound for medical reasons or had interaction with the healthcare system (physician appointment, hospitalization, lab testing) in the three days preceding the recruitment date were excluded from the study. The primary outcome measured was vaccine effectiveness against SARS-CoV-2 infection, confirmed by PCR test, or symptomatic COVID-19, defined as PCR-confirmed infection with any COVID-19 symptoms. Outcomes in the primary analysis were assessed via Kaplan-Meier estimates and per-protocol effect of vaccination. Based on the primary analysis, the estimated vaccine effectiveness against documented infection was 17% (95% Confidence Interval [CI], 7% to 25%) at 14 to 27 days after the first dose. The estimated vaccine effectiveness against documented infection was 51% (95% CI, 39% to 61%) at 7 to 21 days after the second dose. When compared to unvaccinated controls, the absolute risk difference between study groups on days 7 to 21 after the second dose was 1,905 events per 100,000 persons (95% CI, 1,294 to 2,440) for documented infection and 599 events per 100,000 persons (95% CI, 296 to 897) for symptomatic COVID-19. The estimated vaccine effectiveness against symptomatic COVID-19 was 48% (95% CI, 29% to 63%) at 7 to 21 days after the second dose. Overall, this study demonstrates that the Pfizer-BioNTech vaccine provides moderate short-term protection against symptomatic COVID-19 and COVID-19 infection in children aged 5 to 11.
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