Pfizer's COVID-19 vaccine 73% effective in children under 5, updated data shows

Pfizer released new data Tuesday showing its vaccine continues to reduce the risk of COVID-19 in children ages six months to 4 years-old.

Unlike Moderna's two-shot vaccine, Pfizer's vaccine is given as three initial doses for in this age group — considered a "primary" series.

Three doses were 73.2% effective against mild and symptomatic illness from omicron and its subvariants, according to updated data in a Tuesday press release.

Vaccine efficacy is even higher when protecting against severe illness, but the study was not large enough to calculate an exact percentage.

Among children ages 6 through 23 months, the vaccine was 75.8% effective at preventing COVID-19, a median of 1.9 months after the third dose. For children ages 2 through 4 years of age, the vaccine was 71.8% effective at preventing COVID-19, a median of 2.4 months after the third dose.

Sequencing of positive tests found that cases were primarily caused by omicron subvariants, BA.2. Omicron subvariants, BA.4, and BA.5, were just beginning to emerge during the trial, and thus, efficacy results against these strains were inconclusive.

As with doses for adults, officials from Pfizer said they are working with the Food and Drug Administration (FDA) to prepare an emergency use authorization for an Omicron BA.4/BA.5-adapted bivalent vaccine in children 6 months through 11 years of age.

Three doses of the vaccine continues to "be well-tolerated in this age group," the company said, and the "majority of adverse events observed in this age group have been mild or moderate, with a safety profile similar to placebo."

"Building on the strong safety and immunogenicity data that led to FDA authorization of our COVID-19 vaccine for children 6 months through 4 years, we are pleased to share confirmatory evidence that a full course of vaccination helps protect against symptomatic disease, particularly during a time when the Omicron BA.2 strain was predominant," Albert Bourla, Pfizer's chairman and chief executive officer, said in a statement.

Despite a continued push to get young children vaccinated, the vast majority of children under 5 remain completely unvaccinated.

About 941,000 children, under the age of five, have now received their first shot of a COVID-19 vaccine, new federal data shows. The overall total represents less than 5% or approximately 4.8% of the 19.5 million U.S. children in that age group.

When broken down by age group, data shows that the majority of children under 5 who have received at least one shot are between the ages of 2 and 4. About 682,000 kids, ages 2 to 4, have received their first dose, compared to just 259,000 children under the age of 2.

Overall, although about 29.6 million kids 17 years and younger have received at least one vaccine, approximately 43.4 million eligible children remain completely unvaccinated, according to federal data.