The effectiveness of Pfizer’s COVID-19 vaccine against infection turned negative over time for children aged 5 to 11, according to a new study.
Researchers found that for kids in the age group, the effectiveness peaked at 60 percent to 70 percent several weeks after the first dose. It then dropped, nearing zero at week 18 for previously uninfected children and week 20 for previously infected children. After that, the effectiveness was pegged as turning negative, which means the vaccinated children were more likely to contract COVID-19 than unvaccinated children.
