Media outlets are reporting that two individuals who received the Pfizer-BioNTech COVID-19 mRNA vaccine developed severe anaphylactic reactions following the injection.

England's National Health Service (NHS) warned Wednesday that people "with a history of a significant allergic reaction to a vaccine, medicine or food" should not be given the COVID-19 vaccine developed by U.S. pharmaceutical giant Pfizer and Germany's BioNTech. UK's Medical and Health products Regulatory Agency, as reported by The Wall Street Journal, reminded health-care workers that vaccinations should only be carried out in facilities where resuscitation measures are available.

These warnings came after two National Health Service employees who were part of the first tranche to receive the vaccine on Tuesday suffered adverse reactions.

NHS England said in a statement that both of the medical workers who experienced anaphylactoid reactions to the Pfizer vaccine had a "strong past history of allergic reactions."