Target trial emulation of vaccine effectiveness in 5- to 17-years-olds with prior SARS-CoV-2 infection

In this RECOVER study, researchers looked at how well COVID-19 vaccines protected children and adolescents who’d already had COVID-19 from getting it again. Researchers reviewed the electronic health records (EHRs) of nearly 600,000 children ages 5–11 and adolescents ages 12–17. These young people received health care at 37 children’s hospitals located across the US. Researchers compared young people who received at least one COVID-19 vaccine with those who had not. Researchers found that vaccine protection changed as new versions (variants) of SARS-CoV-2, the virus that causes COVID-19, appeared. Early in the Omicron variant period, vaccines lowered the chance of getting COVID-19 again by about 62% in children and 65% in adolescents. In the mid-Omicron variant period, the vaccines lowered the chance of getting COVID-19 again by 57% in children but did not work as well for adolescents. During the later Omicron variant period, the vaccines did not stop children or adolescents from getting COVID-19 again. These findings are important because they show that vaccines offered protection against getting COVID-19 again at first, but that protection became weaker as SARS-CoV-2 changed over time.