Pfizer and BioNTech have reported positive data from a Phase II/III clinical trial in which a two-dose regimen of their Covid-19 vaccine, Comirnaty, demonstrated strong neutralising antibody responses in children aged five to 11 years.

The messenger ribonucleic acid (mRNA) vaccine is approved by the US Food and Drug Administration (FDA) as a two-dose schedule to prevent Covid-19 in people aged 16 years or above.

In the initial stage, the Phase I/II/III trial enrolled up to 4,500 children aged six months to 11 years at more than 90 study centres in the US, Finland, Poland and Spain.

It assessed the safety, tolerability and immunogenicity of the two-dose series of the vaccine administered 21 days apart in three age groups, five to 11 years; two to five and six months to two years.

As per the data from the Phase I dose-escalation part of the trial, subjects aged five to 11 years were given a two-dose regimen of 10µg each while those below five years received 3µg doses in Phase II/III study.

The trial showed that the vaccine had a favourable safety profile in children aged five to 11 years. It was well-tolerated with side effects similar to subjects aged 16 to 25 years.

Furthermore, the antibody responses in subjects receiving 10µg doses were in line with those reported in an earlier study in individuals aged 16 to 25 years immunised with 30µg doses.

Trial data from children below five years are expected to be reported this year, Pfizer said.

Pfizer chairman and CEO Albert Bourla said: “We are eager to extend the protection afforded by the vaccine to this younger population, subject to regulatory authorisation, especially as we track the spread of the Delta variant and the substantial threat it poses to children.

“These trial results provide a strong foundation for seeking authorisation of our vaccine for children five to 11 years old and we plan to submit them to the FDA and other regulators with urgency.”

Pfizer and BioNTech intend to submit the results to the FDA, European Medicines Agency and various other regulatory agencies soon.

The development comes after the FDA’s advisory committee voted unanimously in favour of granting emergency use authorization (EUA) to a booster dose of Comirnaty in people aged 65 years and above.