Protection From COVID-19 Vaccination and Prior SARS-CoV-2 Infection Among Children Aged 6 Months–4 Years, United States, September 2022–April 2023

To understand how coronavirus disease 2019 vaccines impact infection risk in children <5 years, we assessed risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection from September 2022 to April 2023 in 3 cohort studies. There was no difference in risk by vaccination status. While vaccines reduce severe disease, they may not reduce SARS-CoV-2 infections in naïve young children.