A new study published in the New England Journal of Medicine (NEJM) shows not only that the effectiveness of the Pfizer Covid vaccine becomes negative (meaning the vaccinated are more likely to be infected than the unvaccinated) within five months but that the vaccine destroys any protection a person has from natural immunity.

The study is a large observational study that looks at 887,193 children aged 5 to 11 years in North Carolina, of whom 273,157 (30.8%) received at least one dose of Pfizer vaccine between November 1st 2021 and June 3rd 2022. The study includes 193,346 SARS-CoV-2 infections reported between March 11th 2020 and June 3rd 2022.

The researchers used a form of statistical modelling with adjustments for confounding factors (such as underlying conditions) to calculate estimates of vaccine effectiveness over time and against the different Covid variants.