COVID-19 vaccine effectiveness in children under 5 in the USA: a test-negative case-control study
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Background and Objectives
SARS-CoV-2 (COVID-19) continues to mutate, circulate, and adversely impact health and quality of life. While COVID-19 vaccines remain safe and effective, uptake remains low, especially among children, the youngest of whom were not vaccine-eligible until after Omicron and are underrepresented in published research. This study estimated vaccine effectiveness (VE) among under-5-year-olds.
Methods
We used Virginia Department of Health surveillance data from June 2022 through October 2022 to conduct a test negative case-control study. We estimated VE derived from odds ratios (ORs) of reported infections using logistic regression among children aged 6-months to 5-years.
Results
Using the earliest positive (cases) or negative (controls) post-vaccine-eligible test results, the VE associated with two doses of a COVID-19 vaccine was 78% (95% CI=45%, 93%; p=0.004) in unadjusted analyses and 70% (95% CI=25%, 91%, p=0.023) when adjusting for age, sex, prior testing behavior, and prior reported infections. The adjusted VE was 74% (95% CI=28%, 94%; p=0.025) among those with no prior positives reported and 45% (95% CI=-302%, 97%; p=0.569) among those with a prior positive reported.
Conclusions
These results show that even though the vaccine was not closely matched to the dominant variants circulating during the time period analyzed, it was effective at reducing the risk of reported infections. This study adds to the body of knowledge on pediatric COVID-19 VE in an underrepresented age-group and in a rural region, illustrates the utility of surveillance data for evaluation, and can inform vaccine decisions to improve vaccine uptake for young children.
What’s Known on This Subject
SARS-CoV-2 (COVID-19) continues to mutate, circulate, and adversely impact health and quality of life. While research continues to show that COVID-19 vaccines remain safe and effective, uptake remains low, especially among young children who were not vaccine-eligible until after Omicron.
What This Study Adds
Children under-5 are underrepresented in published COVID-19 vaccine effectiveness research. This test negative case-control study estimates VE in this age-group following vaccine approval after the 2022 Omicron wave, using surveillance data from the Virginian Department of Health in Southwest Virginia.
