Pfizer and its German partner BioNTech announced on Thursday that their Omicron booster shots substantially increased antibody protection against the BA.5 subvariant of COVID-19 in preliminary tests.

"The early data suggest that our bivalent vaccine is anticipated to provide better protection against currently circulating variants than the original vaccine,"Pfizer CEO Albert Bourla said in a press statement.

The initial results come from blood samples taken from 40 people between the ages of 18 and 55 and 40 people over the age of 55. Pfizer says there was a substantial boost in antibody protection against the BA.5 subvariant in both groups.

Further data collected from a group of 40 individuals over the age of 55 who had received first generation boosters, but not the omicron-specific booster, indicated only a limited increase in antibodies against BA.5.

The new data is valuable because the Food and Drug Administration approved the Omicron boosters in September without human data on how effectively they would increase antibodies against the BA.5 subvariant of COVID-19.

The preliminary data on BA.5 antibodies from Pfizer's omicron booster comes after the Food and Drug Administration approved its use in children aged 5-11 on Wednesday.

Pfizer says that their Omicron booster is safe in a way that is comparable to prior COVID-19 vaccines.