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Pfizer-BioNTech Vaccine Protection Wanes Quickly in 5 to 11 Year Olds

New research points to vaccine effectiveness against infection dropping from 68% to 12% in this pediatric population within a month.

In a new study, the Pfizer-BioNTech BNT162b2 COVID-19 vaccine was shown to have greatly diminished efficacy and protection against infection within 28-34 days after full vaccination.

“From December 13, 2021 to January 30, 2022, among 852,384 fully-vaccinated children 12-17 years and 365,502 children 5-11 years, [vaccine effectiveness] VE against cases declined from 66% (95% CI: 64%, 67%) to 51% (95% CI: 48%, 54%) for those 12-17 years and from 68% (95% CI: 63%, 72%) to 12% (95% CI: 6%, 16%) for those 5-11 years,” the investigators wrote in their preprint on Medrxiv.

This research was done during the rise of the Omicron variant in the US as the dominant strain, and the investigators noted that significance.

“In the Omicron era, the effectiveness against cases of BNT162b2 declined rapidly for children, particularly those 5-11 years. However, vaccination of children 5-11 years was protective against severe disease and is recommended,” the investigators wrote.

The Food and Drug Administration approved an Emergency Use Authorization (EUA) for the Pfizer-BioNTech vaccine for use in children 5-11 years of age and indicated it for a 2-dose series using 10 µg for each dose, to be administered 3 weeks apart. This EUA happened at the end of October, which was before the rise of Omicron.

Dosing

One potential consideration is the amount of antigen in the current vaccine, according to one vaccine expert. In an interview with NBC News, Peter Hotez, MD, PhD, dean for the National School of Tropical Medicine, Baylor College of Medicine, and co-director of the Center for Vaccine Development at Texas Children’s Hospital said the large drop in the VE may be due in part to the smaller vaccine dosage given to kids 5 to 11.

Hotez said the amount of antigen might not be quite beneficial enough and that there might be a need for a third dose of the vaccine. "It’s looking more likely that at the current lower dose of the Pfizer-BioNTech vaccine for the 5- to 11-year-olds, a third dose may be required," Hotez said.

For their part, Pfizer-BioNTech have been studying their vaccine and its effectiveness against Omicron. At the end of January, they reported 2 lab studies demonstrated that 3 doses of their vaccine elicited antibodies that neutralized the variant.