Two doses of the Pfizer-BioNTech COVID-19 vaccine was protective against severe disease in children aged five to 11 during the recent Omicron variant surge, but quickly lost most of its ability to prevent infection in the age group, according to a study by New York State researchers.

The vaccine’s efficacy against infection among those children declined to 12 per cent at the end of January from 68 per cent in mid-December compared to kids who did not get vaccinated, according the study, which has not yet been peer reviewed.

For those aged 12 to 17, the vaccine’s protection against infection fell to 51 per