Pfizer opens study of COVID-19 shots updated to match Omicron variant
Pfizer has begun a study comparing its original COVID-19 vaccine with doses specially tweaked to match the hugely contagious Omicron variant.
Pfizer and its partner BioNTech announced the study on Tuesday.
COVID-19 vaccine-makers have been updating their shots to better match Omicron in case global health authorities decide the change is needed.
Omicron is more likely than previous variants to cause infection even in people who've been vaccinated, but it's not yet clear that a change to the vaccine recipe will be ordered. Among the issues regulators are weighing: Some of the first places to face an Omicron surge already are seeing the mutant wane -- and there's no way to know if the next variant that arises will resemble Omicron or be totally different.
The original vaccines still offer good protection against severe illness and death. Studies in the U.S. and elsewhere have made clear that adding a booster dose strengthens that protection and improves the chances of avoiding a milder infection.
"We recognize the need to be prepared in the event this protection wanes over time and to potentially help address omicron and new variants in the future," Kathrin Jansen, Pfizer's vaccine research chief, said in a statement.
The new U.S. study is enrolling up to 1,420 healthy adults, ages 18 to 55, to test the updated Omicron-based shots for use as a booster or for primary vaccinations. Researchers will examine the tweaked vaccine's safety and how it revs up the immune system in comparison to the original shots.
Full study results will take many months as volunteers receive multiple vaccine doses -- and as researchers measure how long virus-fighting antibodies remain at high levels after an omicron-adapted dose versus the regular booster.
Pfizer's CEO told CNBC earlier this month that the company could have some Omicron-matched doses ready as early as March. But doing what the company calls "at-risk" manufacturing doesn't mean those doses will be rolled out to the public. Pfizer and other vaccine makers also have brewed and tested experimental doses to match previous variants, changes that ultimately weren't needed but offered valuable practice at tweaking the recipe.
For the new study, one group of about 600 volunteers who received two doses of the current Pfizer vaccine three to six months ago will receive either one or two Omicron-based shots as boosters. Another 600 who've already gotten three regular doses of the Pfizer vaccine will be given a fourth dose of either the regular vaccine or the Omicron-matched version.
The study also will enroll some unvaccinated volunteers who will receive three doses of the Omicron-based vaccine.
Pfizer plans to produce 4 billion vaccine doses in 2022, and said Tuesday the amount isn't expected to change if an Omicron-adapted version is needed.
------
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content
COVID-19 COVERAGE
CTVNews.ca Top Stories
Brokenhearted husband dies after wife slain in Texas rampage
Fourth-grade teacher Irma Garcia was killed in her Texas classroom on Tuesday, massacred along with her co-teacher and 19 students. Two days later, a family member says her brokenhearted husband died.

Gunman's final 90 minutes fuel questions about police delays
The gunman who massacred 19 children and two teachers at a Texas elementary school was inside for more than an hour before he was killed in a shootout, law enforcement authorities said Thursday amid mounting public anger and scrutiny over their response to the rampage.
Man fatally shot by police near Toronto elementary school after reportedly walking streets with rifle
One man is dead after being shot by police near a Toronto elementary school on Thursday afternoon. The incident sent hundreds of students into lockdown.
BREAKING NEWS | Oilers knock off Flames in OT to advance to Western Conference final
The Edmonton Oilers defeated their Alberta rival Calgary Flames 5-4 in overtime in Game 5 of their second-round NHL playoff series Thursday night to advance to the Western Conference final.
'Horrifying experience': 10-year-old boy recounts hiding during deadly Texas school shooting
A 10-year-old boy in a classroom just down the hallway from the room where a gunman killed 19 children and two teachers in Uvalde, Texas on Tuesday said the experience of hiding during the shooting was 'terrifying.'
Trudeau signals new gun-control changes coming; here's what the Liberals have promised
In the wake of a horrific mass shooting at an elementary school in Texas, Prime Minister Justin Trudeau has signalled that the Canadian government will be moving ahead on new gun-control measures 'in the coming weeks.' In previous Parliaments, the Liberals have made changes to Canada's gun laws, but in the 2021 federal election, Trudeau promised to go further.
Russian plane grounded indefinitely at Toronto Pearson racking up huge parking bill
A massive Russian plane that was grounded at Toronto Pearson International Airport back in February is racking up a substantial parking bill.
Monkeypox cases up to 26; first case detected in Ontario: PHAC
There are now 26 confirmed cases of monkeypox in Canada, according to an update from the Public Health Agency of Canada, and the virus has been detected in a new province, with one case in Ontario.
Canada's job vacancies are at a record high
The number of job vacancies across Canada reached an all-time high in March, ending a five-month decline, Statistics Canada said Thursday.