COVID Vaccine Less Effective in Younger Kids

Effectiveness of the Pfizer COVID-19 vaccine (Comirnaty) against infection and hospitalization dropped among kids ages 5 to 11 a little over a month after vaccination, according to real-world data from New York during the Omicron wave.

From Dec. 13, 2021 to Jan. 30, 2022, vaccine effectiveness against infection within 2 weeks of full vaccination dropped from 65% (95% CI 62-68) to 12% (95% CI 8-16) by 28 to 34 days, reported Vajeera Dorabawila, PhD, of the New York State Department of Health, and colleagues.

Moreover, vaccine effectiveness against hospitalization dropped from 100%, albeit with a wide confidence interval (95% CI -189 to 100), to 48% (95% CI -12 to 75), they noted in a study published on the preprint server medRxiv.

Notably, vaccine effectiveness against hospitalization held up much better among kids ages 12 to 17, only dropping from 85% (95% CI 63-95) to 73% (95% CI 53-87). Effectiveness against infection in this age group fell from 76% (95% CI 71-81) to 56% (95% CI 43-63).

All effectiveness estimates among children ages 5 to 11 dropped below those for kids ages 12 to 17 by January 24, the authors noted, with a vaccine effectiveness against infection of 11% (95% CI -3 to 23) for age 11, and 67% (95% CI 62-71) for age 12.