The effectiveness of the Pfizer-BioNTech COVID-19 reduced rapidly in children aged 5-11 years at one month after complete vaccination, but it did offer some protection against severe disease. The effectiveness also decreased in the 12-17-year age group; however, the decline was slower. These findings from a study were posted on the preprint server medRxiv.

Researchers analysed the effectiveness of the Pfizer-BioNTech Covid vaccine against infection and hospitalizations in children in New York state between December 2021 and January 2022 after the emergence of the Omicron variant. Two age groups were defined for the study: 5-11 years and 12-17 years. New lab-confirmed cases and hospitalizations were selected as the primary outcome measure.

From around mid-December through January, the vaccine effectiveness against cases decreased from 66% to 51% among the 852,384 fully-vaccinated children aged 12-17 years and from 68% to 12% among 365,502 children aged 5-11 years. In the last week of January, the vaccine effectiveness against cases further declined to 11% among children aged 11 years. The vaccine effectiveness in children aged 12-17 years was 67% at this time. According to the authors, this could be due to the lower vaccine dose. The vaccine effectiveness against hospitalization also decreased from 85% to 73% among children aged 12-17 years, and from 100% to 48% for those in the 5-11 age group.

The study reiterates the need to continue with protective behaviors (wearing masks, regular handwashing, physical distancing, avoiding crowded and poorly ventilated spaces).

Reference

1. Vajeera Dorabawila, et al. Effectiveness of the BNT162b2 vaccine among children 5-11 and 12-17 years in New York after the emergence of the Omicron Variant. medRxiv, posted February 28, 2022.