Pfizer Inc and its German partner BioNTech on Monday sought the U.S. Food and Drug Administration's authorization for an omicron-tailored COVID-19 vaccine booster for children aged 5 through 11 years.

The application comes just days after Moderna also applied for FDA authorization of its own omicron-targeting shot in adolescents aged 12 to 17 years and children aged six to 11.

The applications represent a step towards getting children vaccinated by a so-called bivalent vaccine, which targets both the original strain of the virus and the circulating BA.4 and BA.5 subvariants of omicron.

The rollout of bivalent booster doses for older age groups has been off to a slow start in the United States compared to the rollout of the first boosters last year, with 4.4 million doses administered so far.

Earlier in the month, the U.S. Centers for Disease Control and Prevention said it expects COVID-19 vaccine boosters targeting circulating variants of the virus to be available for children aged 5-11 years by mid-October.