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Pfizer says early data signals COVID-19 vaccine is effective

Last Updated Nov 9, 2020 at 10:41 am PST

FILE - This May 4, 2020, file photo provided by the University of Maryland School of Medicine, shows the first patient enrolled in Pfizer's COVID-19 coronavirus vaccine clinical trial at the University of Maryland School of Medicine in Baltimore. On Monday, Nov. 9, 2020, Pfizer said an early peek at its vaccine data suggests the shots may be 90% effective at preventing COVID-19. (Courtesy of University of Maryland School of Medicine via AP, File)

Pfizer is out with word the vaccine it's developing prevented more than 90 per cent of infections

An infectious disease expert with Toronto General Hospital says he’s cautiously optimistic about the announcement

Dr. Isaac Bogoch says Canadians won’t be lining up for a vaccine anytime in the near future

As second-wave COVID restrictions tighten in British Columbia, and fears over future shutdowns rise, Pfizer says late-stage trials of its COVID-19 vaccine are showing promising results.

Data verified by an independent monitor suggests the drug, developed in partnership with German-based BioNTech, is 90 per cent effective in stopping transmission of COVID-19 among people who have not been previously infected.

Monday’s announcement doesn’t mean a vaccine is imminent: This interim analysis looks at 94 infections recorded so far in a study of nearly 44,000 people in the U.S. and five other countries.

Dr. Isaac Bogoch, an infectious disease expert with Toronto General Hospital says he’s cautiously optimistic.

“Obviously I’m extremely excited to hear something like this but I’m trying to temper my excitement because this is science by press release and we haven’t seen the data yet,” he says.

“But If this holds up, and these claims are reflected in the data they have, I’ll be extremely excited and the world should be excited, because that would be a major victory,” he adds.

Pfizer Inc. is expected to apply for emergency use through the U.S. Food and Drug Administration within the next week or so, once half of its research subjects have been observed for two months following their second doses.

Bogoch says he’s keen to see more safety data but also wants to learn how the vaccine, which was tested on nearly 44,000 people with diverse backgrounds and races, performs for people of colour.

Still a long wait

Authorities have stressed it’s unlikely any vaccine will arrive much before the end of the year, and limited initial supplies will be rationed. Bogoch says Canadians won’t be lining up for a vaccine anytime in the near future.

“But it tells us that vaccination is probably, I’ve got to be careful with my words, probably on the nearer horizon than on the farther horizon,” says Bogoch.

RELATED: Trudeau says he hopes to see COVID-19 vaccines roll out in Canada in early 2021

If Pfizer’s vaccine ultimately pans out, “it’s going to be a while before this has a major impact at the population level,” said Dr. Jesse Goodman of Georgetown University who is a former chief of the FDA’s vaccine division.

He too cautions that more data is needed to confirm the initial claims of the drug companies, with Pfizer saying it has observed no adverse side effects so far.

“We’re in a position potentially to be able to offer some hope,” Dr. Bill Gruber, Pfizer’s senior vice president of clinical development, told The Associated Press. “We’re very encouraged.”

No participant so far has become severely ill, Gruber said but he could not provide a breakdown of how many infections had occurred in older volunteers, who are at the highest risk from COVID-19.

Canada has bought the rights to 20 million doses of Pfizer’s vaccine, if it proves effective and Health Canada approves it for use here, and Trudeau said the government would purchase more if the initial round goes well.

“We hope to see vaccines landing in the early next year but between now and then it’s really really important that we double down on our efforts,” Trudeau said.

Markets boosted by news of vaccine potential

The interim results were “an interesting first signal,” but questions remain, said Marylyn Addo, head of the tropical medicine unit at UKE hospital in Hamburg, Germany.

Global markets, already buoyed by the victory of U.S. President-elect Joe Biden, exploded on the news from Pfizer. All major markets in Europe, where infections have soared, are up 5 per cent. In the U.S., Dow futures also rose 5 per cent and were up about 1,400 points just over two hours before the opening bell.

The shots made by Pfizer and its German partner BioNTech are among 10 possible vaccine candidates in late-stage testing around the world — four of them so far in huge studies in the U.S. Another U.S. company, Moderna Inc., also has said it hopes to be able to file an application with the FDA later this month.

Neither volunteers nor researchers are aware who received the real vaccine and who was given a placebo, but one week after their second dose, the study began to count participants who developed symptoms of COVID-19 in either group.

Because the study hasn’t ended, Gruber and Pfizer couldn’t say how many in each group became infected.

The FDA is asking Pfizer to continue observing participants until 164 or more infections occur, which will give the agency more data to better tell how well the vaccine is working.

The agency has made clear that any vaccine must be at least 50 per cent effective before moving forward.

Participants were tested only if they developed symptoms, making it unclear whether vaccinated people can be infected but asymptomatic.

The FDA has required that U.S. vaccine candidates be studied in at least 30,000 people. In addition to adequate numbers of older adults, those studies must also include other groups at high risk, including minorities and people with chronic health problems.

And it told companies they must track half their participants for side effects for at least two months, the time period when problems typically crop up. Pfizer expects to reach that milestone later this month, but said Monday no serious safety concerns have been reported.

Because the pandemic is still raging, manufacturers hope to seek permission from governments around the world for emergency use of their vaccines while additional testing continues — allowing them to get to market faster but raising concerns about the validity of the science behind the vaccines.

The FDA’s scientific advisers have expressed nervousness over allowing emergency use of a COVID-19 vaccine, saying it could damage confidence in the drug.

Those advisers said it’s critical these massive studies are allowed to run to completion.

-With files from the Canadian Press


AP writers Frank Jordans and Charles Sheehan contributed to this report.


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.