A medical assistant prepares a dose of a COVID-19 vaccine to be given to a patient. Photo credit: Public Domain image courtesy of Lisa Ferdinando, Department of Defense
One in four patients will experience mild, short-lived systemic side effects after receiving the Pfizer or AstraZeneca vaccine, with headache, fatigue and tenderness being the most common symptoms. Most side effects peaked within the first 24 hours after vaccination and usually lasted 1-2 days.
The study, published today in Lancet Infectious Diseases, is the first large-scale study to compare the two vaccines and examine the prevalence of mild side effects from the UK vaccination program.
Analysis of the data from the ZOE COVID Symptom Study app by researchers at King's College London was reassuring that both the general population experienced far fewer side effects than studies reported with the Pfizer and AstraZeneca vaccines.
The study also reports a significant decrease in infection rates from 12 to 21 days after the first dose of the Pfizer vaccines (58% reduction) and AstraZeneca (39% reduction) compared to a control group. The decrease in infection at least 21 days after the first dose for Pfizer is 69% and for AstraZeneca 60%.
This large-scale analysis examined the differences in reported side effects between the two vaccines currently marketed in the UK. Systemic effects – that is, side effects without the site of injection – included headache, fatigue, chills and chills, diarrhea, fever, arthralgia, myalgia, and nausea. Local side effects – that is, side effects where the injection was in the arm – included pain at the injection site, swelling, tenderness, redness, itching, warmth, and swollen armpits.
Data comes from 627,383 users of the ZOE COVID Symptom Study App who reported systemic and local effects within eight days of receiving a dose or two of the Pfizer vaccine or a dose of the AstraZeneca vaccine between December 8 and March 10 reported.
Summary of results:
- 25.4% of those vaccinated reported having one or more systemic side effects (excluding the area where the injection was made), while 66.2% reported one or more local side effects (at the injection site).
- 13.5% of participants reported side effects after their first dose of Pfizer, 22.0% after their second dose of Pfizer, and 33.7% after their first dose of AstraZeneca.
- The most commonly reported systemic adverse reaction was headache. 7.8% of people reported having headaches after the first Pfizer dose and 13.2% after the second Pfizer dose. 22.8% of people who received the first dose of the AstraZeneca vaccine reported a headache.
- The second most common systemic adverse reaction reported was fatigue. 8.4% and 14.4% of participants reported drowsiness after the first and second doses of the Pfizer vaccine, and 21.1% reported drowsiness after the first dose of the AstraZeneca vaccine.
- The most common local side effect was sensitivity: 57.2% and 50.9% after the first and second doses of the Pfizer vaccine and 49.3% after the first dose of the AstraZeneca vaccine
Importantly, this study shows that side effects were more common in people under the age of 55 and in women.
Participants with a confirmed case of COVID-19 were three times more likely to affect the entire body after receiving Pfizer vaccine doses than participants with no known infection, and almost twice as likely after the first dose of the Pfizer vaccine, AstraZeneca -Vaccine. Local effects were also more common in people with previously known COVID-19 infection.
In Phase III clinical trials with the Pfizer vaccine, the most common adverse reactions were injection site pain (71-83%), fatigue (34-47%) and headache (25-42%), but real analysis found fewer than 30% of users who reported pain at the injection site and less than 10% reported tiredness and headache after the first dose. Similarly, in Phase III studies for the AstraZeneca vaccine, systemic side effects were detected in 88% of the younger participants (18-55 years old) after the first dose, but this study found a significantly lower rate of 46.2% after the first dose.
While side effect rates from clinical trials were much lower than expected, post-vaccine infection rates were calming after two to three weeks and were in line with results from previous studies and the most recent data from the Israeli vaccination program.
Professor Tim Spector OBE, Senior Scientist on the ZOE COVID Symptom Study App and Professor of Genetic Epidemiology at King & # 39; s College London, said: "The data should reassure many people that the effects of the vaccine in the real world are after the effects of the vaccine Vaccines are usually mild and short-lived, especially in those over 50, who are at greatest risk of infection. According to the ZOE app, the rate of new diseases in the UK is at a new low due to a combination of social interventions and vaccinations, and so are we must continue this successful strategy to cover the remaining population ".
"The results also show up to 70% protection after 3 weeks of a single dose. This is fantastic news for the country as more people now have their second bursts."
Dr. Cristina Menni, lead study author from King & # 39; s College London, said: "Our results support the safety of both vaccines with fewer side effects in the general population than indicated in the experimental studies by Pfizer and AstraZeneca and should help address safety concerns in people, who are ready to be vaccinated. "
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Only one in four people have mild systemic side effects from COVID-19 vaccines (2021, April 27).
accessed on April 27, 2021
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