Pfizer says Covid vaccine 90% effective in younger children

The new data was published on the website of the Food and Drug Administration, which has called an advisory panel of independent experts to meet Tuesday to vote on whether to green light the shot.

The analysis was based on around 2,250 trial participants, randomized to receive either the vaccine or a placebo, with data accruing until October 8. Most positive cases occurred when the Delta variant was dominant in the US and globally.

"VE (Vaccine Efficacy) against laboratory-confirmed symptomatic Covid-19 occurring at least 7 days after Dose 2 in evaluable participants without evidence of prior SARS-CoV-2 infection was 90.7%," the document said.

The vaccine was tested with a 10 microgram dose, while older age groups have received 30 micrograms. The doses were administered three weeks apart.

There were no cases of severe Covid and no cases of multisystem inflammatory syndrome in children (MIS-C), a rare but serious post viral condition.

Overall, 158 children aged 5 to 11 have died from Covid in the United States since the start of the pandemic, according to official data.

Pfizer argued that "although the mortality rate for Covid-19 in children is substantially lower than that in adults, Covid-19 was among the top 10 leading causes of death for children 5 to 14 years of age between January and May 2021 in the US."

Safety data was examined among a total of 3,000 vaccinated participants, with a low incidence of severe events.

There were no cases of myocarditis or pericarditis -- inflammation or inflammation around the heart -- but there were not enough study volunteers to be able to detect highly rare side effects. 

In any case, male adolescents and young men are thought to be a higher risk group for these conditions.

This is the first time Pfizer has released an efficacy estimate for its Covid vaccine in younger children, along with a detailed dataset.