BNT162b2 prevents children from getting very sick but does not make them super immune

In the period of COVID-19 pandemic predominated by the milder yet highly transmissible Omicron variant, BNT162b2 vaccination of young children can shield them against severe infection. However, the antiviral armour afforded by this vaccine weakens over time, as reported in a recent study.

“Vaccine effectiveness against infection declined rapidly for children aged 5–11 years, with low protection by 1 month following full-vaccination,” according to a team of investigators led by Dr Vajeera Dorabawila of the New York State Department of Health, Albany, New York, US.

“Among children aged 12–17 years, protection declined substantially, albeit more slowly than observed among younger children,” Dorabawila added.

Between 13 December 2021 and 30 January 2022, the estimated vaccine protection against COVID-19 infections dropped from 66 percent (95 percent confidence interval [CI], 64–67) to 51 percent (95 percent CI, 48–54) for those aged 12–17 years (adolescent group) and from 68 percent (95 percent CI, 63–72) to 12 percent (95 percent CI, 6–16) for those aged 5–11 years (younger age group). [medRxiv 2022;doi:10.1101/2022.02.25.22271454]

Of note, vaccine protection for 11-year-olds was significantly lower than that observed for 12-year-olds despite the overlapping physiology of children at these ages, Dorabawila noted. During the week of 24–30 January, the vaccine effectiveness was estimated to be 11 percent (95 percent CI, -3 to 23) and 67 percent (95 percent CI, 62–71), respectively.

The finding of the lower vaccine protection among children aged 11 vs 12 years suggests the importance of the role of vaccine dose, according to Dorabawila. Those in the adolescent group are given two 30-μg doses, whereas those in the younger age group receive two 10-μg doses.

When it comes to vaccine effectiveness against hospitalization, vaccine protection declined from 85 percent (95 percent CI, 63–95) during 13–19 December to 73 percent (95 percent CI, 53–87) during 24–30 January in the adolescent group, and from 100 percent (95 percent CI, –189 to 100) to 48 percent (95 percent CI, –12 to 75) in the younger age group.

Meanwhile, vaccine protection against COVID-19 infection within 2 weeks of full vaccination (from 13 December 2021 to 2 January 2022) in the adolescent group was 76 percent (95 percent CI, 71–81) but dropped to 56 percent (95 percent CI, 43–63) by 28–34 days. In the younger age group, vaccine protection decreased from 65 percent (95 percent CI, 62–68) to 12 percent (95 percent CI, 8–16) during the same time period.

“Our data support vaccine protection against severe disease among children 5–11 years but suggest rapid loss of protection against infection in the Omicron variant era,” Dorabawila said.

“Should such findings be replicated in other settings, review of the dosing schedule for children 5–11 years appears prudent. At this time, efforts to increase primary vaccination coverage in this age group, which remains <25 percent nationally, should continue,” she pointed out.

Dorabawila also stressed the importance of layered protections, including mask wearing, for children to prevent infection and transmission, given the rapid loss of defence following vaccination.

The investigators used data from three New York State databases. By the week of 24–30 January 2022, 852,384 (62.4 percent) children aged 12–17 years and 365,502 (23.4 percent) children aged 5–11 years had been fully vaccinated.

Published on medRxiv, the study by Dorabawila and colleagues is a preprint and has yet to be peer-reviewed.