The FDA is prone to contemplate allergic reactions to the Pfizer vaccine within the UK earlier than approving use within the US

The two allergic reactions reported by UK health workers vaccinated against Covid-19 are likely under review by the Food and Drug Administration as it decides on the approval of the Pfizer vaccine in the US – although the incident shouldn’t be surprising, they said medical experts on Wednesday.

The UK drug and health products regulator updated its guidelines on Wednesday to advise people with a history of “significant” allergic reactions not to use the vaccine developed by Pfizer and BioNTech. The updated guidelines came after two members of the UK’s National Health Service had allergic reactions to the shot, although they are both recovering well, according to the NHS national medical director.

“We know from extensive clinical studies that this was not a feature. However, if we need to step up our advice after having this experience in vulnerable populations that have been selected as a priority, we will get that advice right there and then.” June Raine, head of MHRA, told a UK government selection committee on Wednesday.

While the Food and Drug Administration will likely review events in the UK before Pfizer’s vaccine is approved in the US, it is not uncommon for people with severe allergic reactions to vaccines not to be included in clinical trials, said Moncef Slaoui, a scientist Advisor to Operation Warp Speed ​​of the White House said during a news conference Wednesday.

The FDA will hold a meeting of its Vaccines and Related Biological Products Advisory Committee (VRBPAC) on Thursday to review Pfizer’s Covid-19 vaccine for approval for emergency use in the United States. If the meeting goes well and the committee votes on approving the vaccine, the FDA could announce its approval “in a matter of days,” Alex Azar, secretary of health and human services, told ABC News This Week on Sunday.

“I suspect this is new news and I would assume – but of course the FDA will make those decisions – that this will be part of the consideration tomorrow,” Slaoui said. The FDA declined to say whether the committee would consider the events in the UK, but a spokeswoman referred to the agenda for Thursday’s meeting, which includes time for a vaccine safety review.

Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, echoed Slaoui’s remarks in an interview with CNBC on Wednesday, saying that people with underlying chronic conditions or people with severe allergic reactions are often excluded from vaccine trials.

If the FDA does not discuss the allergic reactions during Thursday’s meeting, it is possible that they will be discussed in the coming days during a meeting with the Center for Disease Control and Prevention Advisory Committee on Immunization Practices, he said. According to the CDC, the committee is developing recommendations for the use of vaccines to fight disease in the United States.

However, the allergic reactions shouldn’t affect the approval of the vaccine, he added. It’s the type of problem that the committee “routinely deals with because many vaccines are linked to allergic reactions in a small percentage of the population,” Schaffner said.

“They could actually try to exclude certain people for a period of time, or recommend that every vaccination site has equipment so they can efficiently handle allergic reactions,” he said. “You can recommend that people be observed for a short period of time after they have been vaccinated.”

Schaffner said the UK’s decision to temporarily prevent people with a history of severe allergic reactions from receiving Pfizer’s vaccine was “a perfectly reasonable thing” as they continue to investigate the incidents. He said it shows that “the system is working very efficiently because we are doing exactly the same thing here in the US”.

Dr. Syra Madad, senior director of the system-wide program for specific pathogens at New York City Health + Hospitals, said Wednesday that allergic reactions in the UK “are certainly not particularly surprising” but warrant further investigation.

However, Madad added that the UK should have investigated the cases further before issuing a “blanket statement” advising against vaccination for people with severe allergies.

“Lots of these things will happen when these massive campaigns start,” Madad told MSNBC. “I think that’s to be expected.”

– CNBC’s Holly Ellyatt and Berkeley Lovelace Jr. contributed to this report.