Real-World Data Shows Pfizer And AstraZeneca Side Effects Are Less Than Initially Expected

According to a recent study published in the Lancet Infectious Diseases journal, fewer people reported side effects after their Pfizer or AstraZeneca vaccines in the real world when compared to the amount of individuals who experienced side effects in clinical trial settings. 

The study revealed one in four people who got their vaccination from either company reported mild systemic side effects. Systemic reactions are defined as reactions that affect the whole body, so things like injection-site pain don’t count. 

Embed from Getty Images

The findings were also based on data from the ZOE COVID Symptom Study app, which more than 620,000 people in the United Kingdom have used to share their vaccine side effects. According to the data: “far fewer people reported fatigue than in clinical trials. Roughly 14% of app users said they experienced fatigue after their second Pfizer shot, while 63% reported feeling fatigued after either dose during the company’s clinical trials. Among AstraZeneca recipients, about 21% documented fatigue via the app, compared with 53% in trials.”

“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,” Tim Spector, the study’s lead author and an epidemiologist at King’s College London, said in a statement

The ZOE app revealed that headaches were the most commonly reported side effect for the Pfizer vaccine specifically. About 13% of Pfizer recipients said they experienced a headache after their second dose; 55% of clinical trial patients reported having a headache after their second Pfizer dose. 

Embed from Getty Images

For AstraZeneca, about 23% of recipients in the real world reported headache via the app, while 53% of clinical trial participants experienced headaches. Although it’s not a systemic side effect, injection-site pain has also been less common in real world settings. 

84% of all Pfizer clinical trial participants experienced some level of pain where they received their vaccination. Real world data suggests that about 57% of Pfizer recipients experienced soreness after their first dose while 51% reported soreness after the second injection. The AstraZeneca vaccine showed similar results as well. 

It’s important to note that since a lot of the data is based on self-reporting through a smartphone app, there’s obviously room for error as participants may have forgotten to log their side effects, or opted to not log all of them. 

According to Yahoo News: “In J&J’s clinical trials, less than 50% of people reported arm pain, and around 38% reported headaches and fatigue. Nearly 92% of people in the Moderna clinical trials, meanwhile, reported pain at the injection site after the second dose, while nearly 69% reported fatigue, and 63% reported a headache.”

0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *