Britain’s medicine regulator on Wednesday warned anyone with a history of anaphylaxis to a medicine or food to not get the coronavirus vaccine jointly developed by pharmaceutical company Pfizer and biotechnology firm BioNTech. Anaphylaxis is an overreaction of the body’s immune system, which the United Kingdom’s National Health Service describes as severe and sometimes life-threatening, according to Reuters.

In a statement, government-run Medicines and Healthcare Products Regulatory Agency, or MHRA, said that it updated its guidance to coronavirus vaccination centres after two reports of anaphylaxis and one of a possible allergic reaction was reported.

“Any person with a history of anaphylaxis to a vaccine, medicine or food should not receive the Pfizer/BioNTech vaccine,” MHRA chief Chief Executive June Raine. “A second dose should not be given to anyone who has experienced anaphylaxis following administration of the first dose of this vaccine.”

Raine said that most people do not suffer from anaphylaxis and they should consult an healthcare professional if they have severe allergies before getting the second jab of the two-shot vaccine.

“You can be completely confident that this vaccine has met the MHRA’s robust standards of safety, quality and effectiveness,” the MHRA chief said. “We have in place a robust and proactive safety monitoring strategy for Covid-19 vaccines which allows for rapid, real-time safety monitoring at population level. The fact that these incidents were picked up and reviewed shows that to be the case.”

The statement said that the affected individuals received prompt treatment and were recovering well. The regulatory body also advised Covid-19 vaccination centres that those getting inoculated should be monitored for 15 minutes. “Like all medicines and vaccines, this vaccine can cause side effects,” the statement said. “Most of these are mild and short-term, and not everyone gets them.”

Two staff members of the NHS had suffered reactions after taking the vaccine, reported AFP. NHS England Medical Director Stephen Powis said both people had a history of allergic reactions but were recovering well.

The UK has received about 8 lakh vaccine doses in the first batch of an order of 40 million (4 crore). About 40 lakh doses are expected by the end of December. The United Kingdom had on December 2 approved Pfizer-BioNTech’s coronavirus vaccine.

In November, Pfizer had announced a 95% efficacy in the phase three trials of the vaccine. The UK has so far reported 17,71,545 coronavirus cases and the toll stood at 62,663, according to the John Hopkins University data.

Pfizer says some vaccine documents accessed in hacking

Meanwhile, Pfizer and BioNTech on Wednesday said that documents related to development of their Covid-19 vaccine had been “unlawfully accessed” in a cyberattack on European Medicines Agency. In a statement, the companies said their servers were not breached.

However, the companies said they were unaware if any study participants have been identified by the incident. “At this time, we await further information about EMA’s [European Medicines Agency] investigation and will respond appropriately and in accordance with EU [European Union] law,” the statement said.

In a brief statement, the drug regulating agency said that it has launched an investigation into the hacking incident.

Another pharmaceutical company Moderna said it has not received any information from the European regulator about the data breach, reported Bloomberg. “We are engaged with them and monitoring the situation,” Moderna spokesperson said. “Moderna remains highly vigilant to potential cybersecurity threats.”

The hackers pretended to be from one of the world’s largest cold-chain providers, offering refrigeration services necessary for certain vaccines.