Pfizer is looking for US authorization for a third dose of its Covid-19 vaccine, saying Thursday that another shot within 12 months could dramatically bolster immunity and maybe help prevent the latest contagious coronavirus mutant.

Research from multiple countries shows the Pfizer shot and other widely used COVID-19 vaccines offer strong protection against the highly contagious delta variant, which is spreading rapidly around the world and now accounts for most new US infections.

Two doses of most vaccines are essential to develop high levels of virus-fighting antibodies against all versions of the coronavirus, not just the delta variant — and most of the world still is desperate to get those initial protective doses as the pandemic continues to rage.

But antibodies naturally wane over time, so studies also are underway to tell if and when boosters might be needed.

On Thursday, Pfizer’s Dr. Mikael Dolsten told The Associated Press that early data from the company’s booster study suggests people’s antibody levels jump five- to 10-fold after a third dose, compared to their second dose months earlier.

In August, Pfizer plans to ask the Food and Drug Administration for emergency authorization of a third dose, he said.