How Vaccine Side Effects Compare to COVID Symptoms

Side effects of the COVID-19 vaccines are well-known. They can cause fatigue, sore arms, and even fever. Rarely, more serious complications can occur, such as inflammation of the heart. Is it safer to get a vaccine than to try COVID?

This question was answered in a new study published in the New England Journal of Medicine. It compared the mild to severe symptoms experienced by people after receiving the Pfizer vaccine to those associated with COVID infections. (Mild reactions such as fever or soreness at injection sites were not included. Here's what they found

COVID was associated with a significantly higher risk of arrhythmia (irregular heartbeat), myocardial attack (heart attack), deep vein thrombosis, blood clots at the legs, pulmonary embolism and myocarditis.

The risk of lymphadenopathy (swelling of the lymph nodes) was significantly higher for those who received the vaccine.

The study was done as an Israeli medical records analysis. It compared 884.828 vaccinated individuals with equal numbers of unvaccinated controls and 173,106 people suffering from COVID and the same number of controls. Each person was matched with a control of the exact same age, gender, home and health.

This analysis was only applicable to the Pfizer vaccine. Moderna is very similar to Pfizers, so it's likely that the results would be the same if the same study was done with that vaccine. However, without the numbers, we don't know for certain.

These data are even more impressive because of the significant protective effect vaccines have on adverse events like acute kidney injury, intracranial bleeding, and anemia. This is likely due to the fact that infection was prevented, says Grace Lee, a Stanford professor of medicine who wrote an editorial commentary.


She also noted that it is best to compare the risk of getting COVID. If it were a rare condition, you would be more likely to have a serious adverse reaction from the vaccine than to being infected. This could alter the risk/benefit calculation. COVID, as the Delta variant shows, is not a common disease.

She wrote: Given the current global pandemic, however the risk of being exposed to SARS-CoV-2 [the viral that causes COVID] seems to be insurmountable.