The number and nature of suspected adverse reactions to both types of COVID vaccines in use in the UK are not unusual in comparison to other types of routinely used vaccines.
In addition, the overall safety experience with both vaccines is so far as expected from the clinical trials, the UK medicines regulator has said in a safety update.
As with all vaccines and medicines, the safety of COVID-19 vaccines is being continuously monitored via the MHRA’s Yellow Card scheme.
As of 21 February 2021, an estimated 9.4 million first doses of the Pfizer/BioNTech vaccine and 8.4 million doses of the Oxford University/AstraZeneca vaccine had been administered, and around 0.6 million second doses, mostly the Pfizer/BioNTech vaccine, had been administered.
For both vaccines the overall reporting rate is around three to five Yellow Cards per 1,000 doses administered.
For both vaccines, the overwhelming majority of reports relate to injection-site reactions (sore arm for example) and generalised symptoms such as ‘flu-like’ illness, headache, chills, fatigue (tiredness), nausea (feeling sick), fever, dizziness, weakness, aching muscles, and rapid heartbeat.
Generally, these happen shortly after the vaccination and are not associated with more serious or lasting illness.
These types of reactions reflect the normal immune response triggered by the body to the vaccines. They are typically seen with most types of vaccine and tend to resolve within a day or two. The nature of reported suspected side effects is broadly similar across age groups, although, as was seen in clinical trials and as is usually seen with other vaccines, they may be reported more frequently in younger adults.
The Pfizer/BioNTech vaccine was evaluated in clinical trials involving more than 44,000 participants. The most frequent adverse reactions in trials were pain at the injection site, fatigue, headache, myalgia (muscle pains), chills, arthralgia (joint pains), and fever; these were each reported in more than 1 in 10 people.
Adverse reactions were reported less frequently in older adults (over 55 years) than in younger people.
The Oxford University/AstraZeneca vaccine was evaluated in clinical trials involving more than 23,000 participants. The most frequently reported adverse reactions in these trials were injection-site tenderness, injection-site pain, headache, fatigue, myalgia, malaise, pyrexia (fever), chills, arthralgia, and nausea; these were each reported in more than 1 in 10 people. The majority of adverse reactions were mild to moderate in severity and usually resolved within a few days of vaccination. Adverse reactions reported after the second dose were milder and reported less frequently than after the first dose. Adverse reactions were generally milder and reported less frequently in older adults (65 years and older) than in younger people.
The MHRA has issued preliminary guidance on severe allergic reactions after the Pfizer/BioNTech vaccine due to early reports of anaphylaxis. Current advice is that people with a previous history of severe allergic reactions to any ingredients of the vaccine should not receive it. People who receive the vaccine should be monitored for at least 15 minutes afterwards.
Widespread use of the vaccine now suggests that severe allergic reactions to the Pfizer/BioNTech vaccine are very rare. Anaphylaxis can also be a very rare side effect associated with most other vaccines.
Following very substantial exposure across the UK population, no other new safety concerns have been identified from reports received so far.