“It usually occurs soon after vaccination, and can be treated with epinephrine (as in an EpiPen),” explains Harvard Health.
According to the NHS, you should tell healthcare staff before you are vaccinated if you’ve ever had a serious allergic reaction.
“You should not have the COVID-19 vaccine if you have ever had a serious allergic reaction (including anaphylaxis),” warns the health body.
As it points out, staff giving the vaccine are trained to deal with allergic reactions and treat them immediately.