And it may mean people could experience more severe side effects after their second dose of the vaccine.
Figures released from the Medicines and Healthcare products Regulatory Agency (MHRA) show there have been almost 45,000 official reports of side effects from the Pfizer/BioNTech and Oxford/AstraZeneca vaccines.
These are mainly reactions at the site of the jab, such as a sore arm and short-term flu-like feelings, including headache, chills, feeling tired or nauseous, fever, weakness and aching muscles.
The MHRA has also looked at 211 reports of serious allergic reactions – between one and two serious reactions for every 100,000 jabs.
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