This is the group of people who absolutely shouldn’t take the COVID-19 vaccine

Following the first day of coronavirus vaccination rollout in the UK, health officials overseas are now advising people with a “significant history of allergic reactions” to avoid the Pfizer-BioNTech coronavirus shot after two people who were vaccinated suffered adverse reactions.

The UK became the first country to roll out the clinically approved vaccine on Tuesday when 90-year-old Margaret Keenan received the first shot, but two health care workers experienced symptoms on Wednesday, which has the National Health Service England (NHS) asking people with a history of allergic reactions to delay taking the vaccination.

“As is common with new vaccines, the MHRA have 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,” Stephen Powis, medical director for the NHS in England, said in a statement. “Both are recovering well.”

CNN reported that thousands of people received the vaccination on Tuesday, according to NHS England. In the meantime, the MHRA is telling health care professionals to not administer the vaccine to anyone with a signification allergic reaction to a “vaccine, medicine or food — such as previous history of anaphylactoid reaction, or those who have been advised to carry an adrenaline autoinjector,” according to CNN.

While the precaution tends to be common with new vaccines, it is newsworthy since the UK became the first country to approve and administer the vaccine by Pfizer-BioNTech. The Pfizer vaccine was approved the UK health officials on Dec. 2 before being rolled out on Dec. 8, only six days after it was passed.

The vaccine is being offered to those considered highest risk of catching COVID-19, which includes older adults in care homes and frontline health workers, according to health officials. On Tuesday, health care workers and people over 80 were the first to receive the vaccination.

The COVID-19 vaccine requires two doses to be provided for the best protection. The second appointment comes in 21 or 28 days and people should avoid getting pregnant for two months after vaccination, according to NHS. Experts stress that the second dose will give people the best protection against the virus.

Common side effects include experiencing pain or tenderness in the arm where the injection occurred, feeling tired, headache, general aches, or mild flu-like symptoms.

The Food and Drug Administration will make a decision about vaccine candidates to receive emergency-use authorization in the United States on Thursday. Pfizer-BioNTech’s vaccine is expected to be the first to be approved, followed by Moderna’s vaccine, which is expected to be decided on Dec. 17.

If Pfizer’s vaccine is approved by the FDA, vaccinations could start within days in the US.

Canada approved the same Pfizer-BioNTech vaccine on Wednesday.

More than 15 million cases of the coronavirus have been confirmed in the US since March, resulting in at least 286,000 deaths country-wide.