The new data were published on the website of the Food and Drug Administration, which has called an advisory panel of independent experts to meet Tuesday to decide whether to authorise the vaccine in this age group.
The analysis was based on around 2,250 trial participants with data accruing until October 8, and 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.
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.
There were no cases of myocarditis or pericarditis (heart inflammation or inflammation around the heart) but there are not enough study volunteers to be able to detect highly rare side effects, and male adolescents are thought to be a higher risk group.
This is the first time Pfiser has released an efficacy estimate for its Covid vaccine in younger children. Its earlier press statement only said the shot produced a robust immune response.
The vaccine was tested with a 10 microgram dose, while older age groups have received 30 micrograms.
The administration of President Joe Biden has said it stands ready to roll out shots for the country’s 28 million 5 to 11-year-olds as soon as the vaccine is authorised by science agencies.