Pfizer announced yesterday 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 US still offer strong protection against severe COVID-19 disease and death — especially if people have gotten a booster dose.

However 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.

They also tested whether to keep today’s standard dosage — 30 micrograms — or to double the shots’ strength.

In a study of more than one thousand 200 middle-aged and older adults who’d already had three vaccine doses, Pfizer said both booster approaches spurred a substantial jump in Omicron-fighting antibodies.