By LAURAN NEERGAARD Medical Writer AP
Pfizer said on Wednesday that a booster of its COVID-19 vaccine could offer significant protection against the new omicron variant even if the initial two doses appear significantly less effective.
Pfizer and its partner BioNTech have said that although two doses may not be strong enough to prevent infection, lab tests have shown that one booster increases the levels of antibodies in people able to fight off 25 times. omicron. For people who have yet to receive a booster, the companies said two doses should still prevent serious illness or death.
Health officials in the United States and other countries have urged those eligible to receive a third dose even before these results.
“Go get your third boost as soon as possible,” Dr. Mikael Dolsten, Pfizer chief scientific officer, told The Associated Press. “It’s heartwarming and a very positive message that we now have a plan that will induce immunity that can protect against infections, symptomatic illnesses and serious illnesses from now on throughout the winter season.”
President Joe Biden said the discovery of the Pfizer booster is “very encouraging” although he cautioned, “the lab report says. There are more studies underway.
Pfizer and BioNTech tested blood samples taken a month after a booster and found that people had levels of omicron neutralizing antibodies similar to amounts proven to protect against previous variants after two doses. For lab testing, the researchers grew samples of so-called “pseudoviruses” that contain the disturbing new mutations.
Scientists do not yet know how much of a threat the omicron variant is. Currently, the extra-contagious delta variant is responsible for most cases of COVID-19 in the United States and other countries.
But the omicron variant, discovered late last month, carries an unusually high number of mutations and scientists are rushing to find out how easily it spreads, whether it causes more severe or milder disease than other types of coronavirus. – and to what extent it could escape the protection of previous vaccinations.
Pfizer’s findings, announced in a press release, are preliminary and have not yet been scientifically reviewed. But they’re the first from a vaccine maker to examine whether the booster doses health officials are urging people to get can actually make a key difference.
Moderna and Johnson & Johnson are also testing their vaccine performance, but health officials will be watching closely for actual evidence of the spread of omicron in highly vaccinated populations.
If it becomes dominant and causes serious illness, then regulators will have to decide whether the vaccines need to be changed to better match omicron – changes to the recipe that manufacturers are already starting, just in case.
Scientists have speculated that the high jump in antibodies that accompanies a third dose of current COVID-19 vaccines may be enough to counter any decrease in effectiveness.
Despite the large number of mutations that omicron carries, “it’s still not a full-exhaust variant, it’s a partial-exhaust variant,” Ugur Sahin, CEO of BioNTech, told a press conference. .
Antibody levels predict how well a vaccine can prevent coronavirus infection, but they’re just one layer of the immune system’s defenses. Pfizer said two doses of the vaccine should always protect against serious illness because mutations in omicron don’t appear to hamper another defense – T cells that fight the virus after infection.
A small lab study in South Africa also concluded that people may be more susceptible to breakthrough omicron infections after just two doses of Pfizer. Scientists at the Africa Health Research Institute in Durban found a large drop in the strength of antibodies to omicron compared to other variants, although they did not test the boosters. Pfizer boosters are not yet available in South Africa, but health workers are offered additional doses of the single-injection J&J vaccine.
Preliminary South African results suggest that people vaccinated after a previous episode of COVID-19 retained more protection – reflecting that the initial injections are known to trigger a huge jump in antibodies after a previous infection.
Even though there are more breakthrough infections after two doses, most experts believe the vaccines will still work against the omicron variant because of the other immune defenses they trigger, said Willem Hanekom, co-author of the South African study.
“The more antibodies you can have on board, the better you’ll do, at least in these lab experiments,” Hanekom said. “So the booster shots could be very important. “
An American expert agreed that the preliminary results of the recall are encouraging, although more information is needed.
But if omicron ends up causing serious illness and becomes common around the world, “it may be much better treated with vaccines adjusted to specifically protect against this variant,” said Dr Jesse Goodman of Georgetown University, former head of vaccines for the Food and Drug Administration. .
Vaccine makers are already tweaking their vaccine recipes to create a specific dose for omicron in case it’s needed. Pfizer has predicted that its candidate could be ready for review by regulators in March.
Associated Press reporters Andrew Meldrum and Frank Jordans contributed to this report.