Two staffers with Britain’s National Health Service manifested symptoms of “anaphylactoid reaction” after receiving the vaccinations at a hospital Tuesday.
NHS officials said both workers have a history of serious allergies and carry epinephrine injectors — often called EpiPens — for the emergency treatment of acute reactions, which can include rashes, low blood pressure, constricted airways and dizziness or fainting.
“Both are recovering well,” said NHS Medical Director Stephen Powis.
As is common with new vaccines, Britain’s Medicines and Healthcare Products Regulatory Agency (MHRA) has “advised on a precautionary basis that people with a significant history of allergic reactions do not receive this vaccination, after two people with a history of significant allergic reactions responded adversely yesterday,” Powis said.
Health officials in Britain quickly sought to calm nerves by noting that the nurses and pharmacists who give vaccines are prepared to deal with allergic reactions and that such reactions are rare.
Typically, even for flu shots, people with a history of allergic reactions are urged to consult with their doctors before getting any vaccine.
Still, there was concerns that the “vaccine hesitant” and those opposed to vaccines in general could focus on the negative news, undermining efforts to combat the pandemic.
The two-shot Pfizer vaccine appears to be on the cusp of regulatory clearance in the United States, after a 53-page review published Tuesday by the Food and Drug Administration confirmed that the vaccine meets the standard for emergency-use authorization. The federal government has ordered 100 million doses, which can start being delivered as soon as regulators give the go-ahead.
A spokeswoman for Pfizer said the pharmaceutical giant, which developed the vaccine with the German firm BioNTech, were advised by British regulators of two “yellow card reports” associated with allergic reactions to the vaccine. Yellow cards are issued in Britain when drugs or vaccines cause side effects, which must be reported.
“As a precautionary measure, the MHRA has issued temporary guidance to the NHS while it conducts an investigation in order to fully understand each case and its causes. Pfizer and BioNTech are supporting the MHRA in the investigation,” the drug company said.
“In the pivotal Phase 3 clinical trial, this vaccine was generally well tolerated with no serious safety concerns reported by the independent Data Monitoring Committee,” it said. “The trial has enrolled over 44,000 participants to date, over 42,000 of whom have received a second vaccination.”
On the first day of the rollout in Britain, “several thousand” people received injections at 50 hospitals in England, with shots offered in Wales, Scotland and Northern Ireland, as well. Britain hopes to inoculate as many as 2 million people by the end of the year.
The NHS is prioritizing those age 80 and older, alongside workers in nursing homes, for the first shots. If doses are left over at the end of the day, front-line medical workers at hospitals are being invited to receive a dose, too.
In remarks to journalists distributed via Britain’s Science Media Center, Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, said: “Allergic reaction occurs with quite a number of vaccines, and perhaps even more frequently with drugs. So it is not unexpected.”
Evans said the Pfizer data showed that about 0.6 percent of people had some form of allergic reaction to the vaccine in the clinical trials (although 0.5 percent also had a reaction to the placebo).
So there was a genuine excess of allergic reaction, but it was small and the true rate is not known, he said, adding that there is a lot of uncertainty around that estimate.
The FDA found slightly more adverse events “potentially representing allergic reactions” in its review of the Pfizer data. There were 137 “hypersensitivity-related” reactions to the vaccine, compared with 111 such events in the placebo group.
In a briefing with reporters Wednesday, Moncef Slaoui, science adviser for the White House’s Operation Warp Speed task force, said he assumes the FDA will consider possible allergic side effects in its review of the Pfizer vaccine. “Subjects with known severe allergic reactions should not take the vaccine until we understand exactly what happened here,” Slaoui said.
Evans said “what would be wise,” as British regulators advised Wednesday, “would be for anyone who has known severe allergic reaction, such that they need to carry an EpiPen, to delay having a vaccination until the reason for the allergic reaction has been clarified.”
Adam Finn, a professor of pediatrics at the University of Bristol, added via the Science Media Center: “Severe allergic reactions to vaccines are unusual but staff administering vaccines are always trained and equipped to deal with them in the event they occur.
“The report of occurrence of two reactions. . . will heighten awareness of this possibility among immunising teams and sensible precautions to avoid exposure of those who have had previous severe allergic reactions are being proposed while more experience of using this new vaccine accumulates.”
Cunningham reported from Istanbul. Carolyn Johnson and Isaac Stanley-Becker in Washington contributed to this report.