One in four people experience mild, short lived systemic side effects after receiving the Covishield COVID-19 vaccine with fatigue, headache and tenderness being the most common symptoms, says a study published in the Lancet Infectious Disease journal.
Researchers from King’s College London in the UK also found that the most systemic side effects, meaning side effects excluding where the injection took place, peaked within 24 hours following vaccination and usually lasted one to two days. The analysis of data from ZOE COVID Symptom Study app found much fewer side effects in the general population with both the Pfizer and AstraZeneca vaccines than reported in trials.
The study also reports a significant decrease of infection rates from 12 to 21 days after the first dose of the Pfizer (58% reduction) and AstraZeneca (39% reduction) vaccines compared to a control group. The drop in infection at least 21 days after the first dose for Pfizer is 69% and for AstraZeneca 60%, says the study. Systemic effects included headache, fatigue, chills and shiver, diarrhoea, fever, arthralgia, myalgia and nausea. Local side effects included pain at the site of injection, swelling, tenderness, redness, itch, warmth and swollen armpit glands.
Professor Tim Spector, lead scientist on the ZOE COVID Symptom Study app and Professor at King’s College London, 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 50’s who are most at risk of the infection.
The study also found that side effects were more common among people under 55 years of age and among women. Participants who had confirmed case of prior COVID-19 were three times more likely to have side effects that affect the whole body after receiving doses of the Pfizer vaccine than those without known infection. And those with a confirmed case of prior COVID-19 number were almost twice more likely to have side effects that affect the whole body after the first dose of the AstraZeneca vaccine.
The researchers noted that in Phase III clinical trials of the Pfizer vaccine, the most common side effects were pain at the injection site (71-83%), fatigue (34-47%) and headache (25-42%). However, the real world analysis found less than 30% of users complained of injection site pain and less than 10% of fatigue and headache after the first dose.