Dec 25, 2020 - Health

Scientists suspect compound in allergic reactions to Pfizer vaccine

Picture of a patient receiving the Pfizer-BioNTech coronavirus vaccine
Photo: Mario Tama/Getty Images

Scientists believe the compound polyethylene glycol — known as PEG — is to blame for the reported allergic reactions to the Pfizer-BioNTech coronavirus vaccine, the Wall Street Journal reports.

Driving the news: The Centers for Disease Control and Prevention identified six allergic reactions to the vaccine out of the 272,001 doses given through Dec. 19.

  • No allergic reactions have been reported for the Moderna vaccine, which also contains PEG. The Food and Drug Administration said it will be following the vaccine's rollout "very closely," according to WSJ.
  • The U.K. reported two severe reactions to the vaccine on Dec. 8.

What they're saying: "What we’re learning now is that those allergic reactions could be somewhat more common than the highly uncommon that we thought they were because people do get exposed to polyethylene glycol in various pharmaceutical preparations," said Peter Marks, director of the Food and Drug Administration’s Center for Biologics Evaluation and Research, per WSJ.

Worth noting: "PEG has never been used before in an approved vaccine, but it is found in many drugs that have occasionally triggered anaphylaxis," the journal Science writes.

  • However, scientists say PEG-induced allergic reactions are uncommon and also suspect that people could have reacted to a different compound in the Pfizer-BioNTech vaccine.

The bottom line: Scientists still argue that vaccination must continue despite the suspected reactions to PEG, although more data is needed.

  • "We need to get vaccinated," Elizabeth Phillips, a drug hypersensitivity researcher at Vanderbilt University Medical Center, told Science. “We need to try and curtail this pandemic."
Go deeper