In a statement on Friday, Health Canada and the Public Health Agency of Canada stated that health regulators “have not received an application from Pfizer to approve the COVID-19 booster injection.”

The two companies did not share data showing this risk, but said they would make it public soon. Pfizer said it is scheduled to meet with US federal health officials on Monday to discuss the matter.

In an interview with Reuters, some leading vaccine experts questioned Pfizer’s reasoning and said that more data is needed to justify boosting vaccines, especially as many countries are striving to manage the initial vaccine dose required to protect their citizens. .

Dr. Larry Corey, a virologist at the Fred Hutchinson Cancer Center in Seattle, said: “It’s disappointing that they made such a complicated decision and took such a one-sided approach.” He is overseeing US government support. COVID-19 vaccine trial.

Delta variants are on the rise

The rise of delta variants, first discovered in India, is now the main form of new coronavirus infection in many countries, which has raised concerns about whether the currently available vaccines provide adequate protection. Several experts said that if vaccinated people are hospitalized or the number of deaths increases significantly, booster injections are necessary.

“This is the booster route,” said Dr. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia and a vaccine consultant at the U.S. Food and Drug Administration.

He said that so far, this is not the case in the United States. In the United States, the vast majority of serious diseases occur in people who have not been vaccinated.

Soon after Pfizer announced the news late on Thursday, US health officials tried to assure the public that anyone who had already received two doses of the drugmaker’s vaccine would be protected from serious illness and death, even with delta variants. is also like this.

The US Food and Drug Administration and the Centers for Disease Control and Prevention said in a statement: “Americans who have been fully vaccinated do not need booster injections at this time.”

A Pfizer spokesperson declined to comment on the criticism.

Pfizer cites Israeli data

Pfizer CEO Albert Bourla and other officials have said for months that they expect regular booster injections for COVID-19, and this prospect may help the company’s profitability in the next few years.

In explaining its decision to seek emergency authorization, Pfizer cited the survey results released by the Israeli Ministry of Health last week, which showed that the vaccine is only 64 effective in preventing transmission and mild disease in the face of delta variants. %. The ministry stated that it is still 93% effective in preventing hospitalizations and deaths.

Mikael Dolsten, Pfizer’s chief science officer, told Reuters that Israeli data showed that the protection of individuals vaccinated in January or February was weakened.

Scott Gottlieb, a member of the Pfizer board of directors, told CNBC that vaccinated people include those who are older and have experienced asymptomatic or mild COVID.

“Frankly, you don’t want them to get any infections because of the uncertainty of elderly infections and the risk of elderly infections,” he said. “That’s why I believe…For those elderly who have just been vaccinated into the fall and winter, boosters may be an option.”

However, the Israeli Ministry of Health has not released any data showing a specific correlation between the vaccinated person’s infection and the date of vaccination. On Sunday, the government said it would provide boosters to adults with weakened immune systems and a higher risk of severe COVID.

“I don’t know of valid clinical evidence from Israel that the risk of breakthrough infections is higher, let alone serious illnesses, which are related to six months or more after vaccination-no methodologically sound analysis shows causality. The relationship goes beyond early descriptive cues,” said Ran Balicer of health care provider HMO Clalit and the chairman of the Israeli government’s COVID-19 expert advisory group.

“I’m not saying it’s impossible, but I haven’t seen such evidence so far,” he said.

U.S. supports modern research

Corey said that it is not yet clear what caused the decline in efficacy. “Is it really because of the drop in antibody levels, or other reasons?”

The US government is supporting Moderna’s two studies on similar vaccines, which may provide more insights into how vaccines combat delta variants. These results are expected to be announced in late autumn.

Dr. William Schaffner, a vaccine expert at the Vanderbilt University Medical Center in Nashville, said that Pfizer’s own preliminary data showed that the third dose of the vaccine would produce a new peak in antibody levels, just in case, which encouraged him. .

“But now the argument supporting the booster, I don’t think it is convincing,” he said.