Pfizer says tweaked COVID-19 shots boost omicron protection

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.

Pfizer and its partner BioNTech studied two different ways of updating their shots -- targeting just omicron, or a combination booster that adds omicron protection to the original vaccine.