Pfizer Says Tweaked COVID-19 Shots Boost Omicron Protection

Pfizer's Omicron-only booster sparked the strongest immune response against that variant.

Pfizer announced Saturday that tweaking its COVID-19 vaccine to better target the Omicron variant is safe and works — just days before regulators debate whether to offer Americans updated booster shots this fall.

The vaccines currently used in the U.S. still offer strong protection against severe COVID-19 disease and death -- especially if people have gotten a booster dose. But those vaccines target the original coronavirus strain and their effectiveness against any infection dropped markedly when the super-contagious Omicron mutant emerged.

Now with Omicron's even more transmissible relatives spreading widely, the Food and Drug Administration is considering ordering a recipe change for the vaccines made by both Pfizer and rival Moderna in hopes that modified boosters could better protect against another COVID-19 surge expected this fall and winter.