The United Kingdom's Medicines and Healthcare products Regulatory Agency (M.H.R.A.) updated its guidance on Wednesday to advise those who have ever previously experienced adverse allergic reactions to vaccines to not to use the Pfizer (NYSE: PFE)-BioNTech (NASDAQ: BNTX) shot.
The new guidance comes after two members of Britain's National Health Service experienced severe allergic reactions that required medical attention. The two individuals have since recovered.
"Any person with a history of anaphylaxis to a vaccine, medicine or food should not receive the Pfizer BioNTech vaccine. A second dose should not be given to anyone who have experienced anaphylaxis following administration of the first dose of this vaccine," Dr. June Raine, chief executive of the M.H.R.A., issued in a statement.
"Anaphylaxis is known, although very rare, side effect with any vaccine. Most people will not get anaphylaxis and the benefit in protecting people against COVID-19 outweighs the risks," Raine added.
This U.K.'s new guidance comes ahead of the U.S. Food and Drug Administration's (F.D.A.) meeting of its Vaccines and Related Biological Products Advisory Committee on Thursday to review the Pfizer-BioNTech for emergency use authorization.
While the F.D.A. is likely review the adverse side effects seen in the U.K. before authorizing the vaccine, the severe adverse side effect is most likely not going to affect the committee's decision. The agency could authorize the vaccine within the next few days.
The U.S. federal government has prepared 2.9 million coronavirus vaccine doses to be distributed throughout the country immediately after the F.D.A. clears the Pfizer-BioNTech shot for emergency public use. Officials stated that an additional 2.9 million vaccines will be available in the weeks following to provide the required second dose.
The Pfizer-BioNTech vaccine uses new messenger RNA (mRNA) technology, which takes a piece of genetic code that contains instructions for the body to develop proteins that trigger an immune system response. Other common vaccines, like the flu shot for comparison, use weakened or inactivated forms of a virus to trigger similar antibody responses in an individual. Both vaccine technologies work towards the common goal of preventing infections and protecting a population from further widespread disease.