One in four people experiences mild, short-lived systemic side-effects after receiving either the Pfizer or AstraZeneca coronavirus vaccine, new research suggests.
Headache, fatigue and tenderness are the most common symptoms, with most effects peaking within 24 hours after vaccination, usually lasting one to two days, according to the study.
The paper, published in the Lancet Infectious Diseases, compared both jabs and investigated the prevalence of mild side-effects of the UK’s vaccination programme.
The analysis by researchers from King’s College London of data from the Zoe Covid Symptom Study app found fewer side-effects in the general population with both the Pfizer and AstraZeneca vaccines than reported in trials.
Tim Spector, professor of genetic epidemiology at King’s College London and lead scientist on the app, said: “The data should reassure many people that, in the real world, after-effects of the vaccine are usually mild and short-lived, especially in the over-50s, who are most at risk of the infection.
"The results also show up to 70 per cent protection after three weeks following a single dose, which is fantastic news for the country, especially as more people have now had their second jabs.”
Decrease of infection rates
The study also reports a decrease of infection rates from 12 to 21 days after the first dose of the Pfizer (58 per cent reduction) and AstraZeneca (39 per cent reduction) vaccines compared with a control group.
According to the research, the drop in infection at least 21 days after the first dose for Pfizer is 69 per cent and 60 per cent for AstraZeneca.
The analysis looked at the differences of reported side-effects from the first two vaccines that were available.
Systemic effects – meaning side-effects excluding the injection site – included headache, fatigue, chills and shiver, diarrhoea, fever, arthralgia (joint pain), myalgia (muscle pain), and nausea.
Local side-effects – where the injection took place in the arm – included pain, swelling, tenderness, redness, itch, warmth and swollen armpit glands.
The data comes from 627,383 users of the Zoe Covid Symptom Study app who self-reported systemic and local effects within eight days of receiving one or two doses of the Pfizer vaccine or one dose of the AstraZeneca vaccine between December 8th and March 10th.
Overall, the study found that 25.4 per cent of vaccinated people indicated suffering from one or more systemic side-effects, whereas 66.2 per cent reported one or more local side-effects.
Around 13. per cent of participants reported side-effects after their first Pfizer dose, 22 per cent after the second Pfizer dose and 33.7 per cnet after the first AstraZeneca dose.