Pfizer vaccine significantly less effective in kids 5-11: study

by Peter Sullivan - 02/28/22 1:37 PM ET

The Pfizer coronavirus vaccine is significantly less effective in children aged 5 to 11 than it is in older kids, a new study found, raising questions about the correct dose to give to the young.

The study from researchers at the New York State Department of Health found that vaccine effectiveness against COVID-19 infection among children 5 to 11 declined from 68 percent to just 12 percent over the period of Dec. 13 to Jan. 30.

Effectiveness was higher for those aged 12 to 17, declining from 66 percent to 51 percent over the same period.

Children under 12 receive a dose that is one-third the size given to those 12 and up, which could explain the drop in effectiveness.

The study notes that effectiveness for children aged 5 to 11 was better against severe disease and that vaccination is still recommended.

The vaccine’s effectiveness against hospitalization among children 5 to 11 declined from 100 percent to 48 percent, compared with 85 percent to 73 percent for older children.

The results highlight the challenges that vaccines for children have faced. Pfizer earlier this month delayed the timeline for its vaccine for children under 5, saying more time was needed to test a third dose.

The dose being tested in children under 5 is even smaller.

“These results highlight the potential need to study alternative vaccine dosing for children and the continued importance layered protections, including mask wearing, to prevent infection and transmission,” the study stated.

Still, the analysis said vaccination should continue in children under 12, an area where rates have been lagging.

“At this time, efforts to increase primary vaccination coverage in this age group, which remains [less than] 25% nationally, should continue,” it said.

The findings also could complicate the debate about masking in schools, as many areas are removing their school mask mandates.

Asked about the results, a Pfizer spokesperson said the company is “confident in the protection and safety of our COVID-19 vaccine” and has a “robust booster research program for adolescents.”