Pfizer significantly less effective in kids 5-11

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.

Possible reason: 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.

Big picture: 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.