Pfizer Says Modified COVID Vaccines Increase Omicron’s Protection

pfizer announced Saturday that modifying its COVID-19 vaccine to better target the omicron variant is safe and working — just days before regulators debate whether to offer Americans updated booster shots this fall.

The vaccines currently in use in the US still provide strong protection against severe COVID-19 illness and death – especially if people have been given a booster dose. But those vaccines target the original coronavirus strain, and their effectiveness against any infection dropped significantly when the super-infectious omicron mutant showed up.

With omicron’s even more transmissible relatives proliferating, the Food and Drug Administration is considering ordering a prescription change to the vaccines made by both Pfizer and rival Moderna in the hopes that modified boosters could better protect against a new one. COVID-19 wave expected this fall and winter.

Pfizer and its partner BioNTech have explored two different ways to update their injections: targeting omicron alone or a combination booster that adds omicron protection to the original vaccine. They also tested whether to keep the current standard dosage — 30 micrograms — or double the strength of the injections.

In a study of more than 1,200 middle-aged and older adults who had already had three doses of vaccine, Pfizer said both booster approaches caused a substantial jump in omicron-fighting antibodies.

“Based on this data, we believe we have two very strong ommicron-adapted candidates,” Pfizer CEO Albert Bourla said in a statement.

Pfizer’s ommicron-only booster elicited the strongest immune response against that variant.

But many experts say combination injections may be the best approach, as they would retain the proven benefits of the original COVID-19 vaccine while adding new protection against ommicrons. And Pfizer said that a month after people got the combo shot, they had a 9 to 11-fold increase in omicron-fighting antibodies. That is more than 1.5 times better than another dose of the original vaccine.

More importantly, preliminary lab studies show that the modified shots also produce antibodies capable of fighting the genetically distinct relatives of omicron called BA.4 and BA.5, although those levels weren’t nearly as high.

Moderna recently announced similar results from tests of its combination injection, which scientists call a “bivalent” vaccine.

The studies were not designed to track how well-updated boosters have prevented COVID-19 cases. Nor is it clear how long any additional protection would last.

But the FDA’s scientific advisers will publicly debate the data on Tuesday as they grapple with whether or not to recommend a change to vaccine prescriptions — ahead of similar decisions by other countries.

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