The Pfizer Vaccine May Not Provide The Same Protection For All Children

A US study looked at the effectiveness of the Pfizer jab for kids during the Omicron surge.
Dobrila Vignjevic via Getty Images

The Pfizer vaccine may be less effective at stopping Covid infection in children aged five to 11 than in children aged 12 to 17, a new US study suggests.

New York State researchers found that among five- to 11-year-olds who had received the Pfizer jab, protection fell by 56% during the winter Omicron surge (from 68% to 12%), while in children aged 12 to 17, it only fell by 15%.

The findings come after it was announced that Covid vaccines are due to be given to children aged five to 11 in England from some point in April.

In the US, younger children receive a lower 10-microgram dose of the vaccine than 12- to 17-year-olds, who receive the same 30-microgram dose as adults and are eligible for a third booster shot.

This new study suggest scientists may need to explore different vaccine dosing for children, though some medical experts have questioned whether the study data was robust enough to be sure the vaccine’s protection had declined.

“The goal of the vaccine is to protect against severe illness – to keep children out of the hospital,” Dr. Paul Offit, a paediatric infectious disease expert at Children’s Hospital of Philadelphia said, who added that it wasn’t a surprise protection waned against mild illness from the Omicron variant, as it is “somewhat immune evasive for protection against mild illness”.

The UK medical regulator, the Medicines and Healthcare Products Regulatory Agency (MHRA), approved the use of Pfizer vaccines for children five to 11 last year but it wasn’t until February 2022 that health secretary Sajid Javid said that the vaccine programme would be rolled out to include children in that age group, with a date in April still expected to be announced.

“Children without underlying health conditions are at low risk of serious illness from Covid-19 and the priority remains for the NHS to offer vaccines and boosters to adults and vulnerable young people, as well as to catch-up with other childhood immunisation programmes,” Javid said.

Experts are still learning about Covid-19. The information in this story is what was known or available at the time of publication, but guidance could change as scientists discover more about the virus. To keep up to date with health advice and cases in your area, visit and