Matt Rourke / AP
Pfizer announced on Saturday that adjusting its COVID-19 vaccine to better target the omicron variant is safe and effective – just days before regulators discuss whether to offer Americans updated booster shots this fall.
The vaccines currently used in the United States still offer strong protection against serious COVID-19 disease and death – especially if people have been given a booster dose. However, these vaccines target the original coronavirus strain, and their effectiveness against any infection dropped markedly when the super-infectious omicron mutant emerged.
Now with omicron’s even more contagious relatives spreading, the Food and Drug Administration is considering ordering a prescription change for the vaccines made by both Pfizer and rival Moderna in the hope that modified boosters can better protect against another COVID-19 rise that is expected this autumn and winter.
Pfizer and partner BioNTech studied two different ways to update their images – aimed at omicron only, or a combination amplifier that adds omicron protection to the original vaccine. They also tested whether they should keep the current standard dose – 30 micrograms – or double the firing strength.
In a study of more than 1,200 middle-aged and older adults who had already had three vaccine doses, Pfizer said both booster approaches spurred a significant jump in omicron-fighting antibodies.
“Based on this data, we believe we have two very strong omicron-matched candidates,” Pfizer CEO Albert Bourla said in a statement.
Pfizer’s omicron-only booster triggered the strongest immune response to that variant.
However, many experts say that combination shots may be the best approach because they will retain the proven benefits of the original COVID-19 vaccine while providing new protection against omicron. And Pfizer said a month after people received the combination shot, they had a 9 to 11-fold increase in omicron-fighting antibodies. It is more than 1.5 times better than another dose of the original vaccine.
And more importantly, preliminary laboratory studies show that the adjusted shoots also produce antibodies that are able to fight omicron’s genetically distinct relatives called BA.4 and BA.5, although these levels were not nearly as high.
Moderna recently announced similar results from tests of the combination syringe, what researchers call a “bivalent” vaccine.
The studies were not designed to track how well-updated boosters prevented COVID-19 cases. It is also not clear how long an extra protection will last.
But the FDA’s scientific advisers will publicly debate the data on Tuesday, as they fight over whether to recommend a change in vaccine prescriptions – ahead of similar decisions from other countries.