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Why do some people experience side effects after COVID-19 vaccines?


Why do some people experience side effects after COVID-19 vaccines?

Temporary side effects, including headache, fatigue and fever, are signs that the immune system is waking up – a normal response to vaccines. And they are common.

“The day after getting these vaccines, I wasn’t planning anything that would be strenuous physical activity,” said Dr Peter Marks, head of vaccines for the US Food and Drug Administration, who felt tired after his first. dose.

Here’s what happens: The immune system has two main arms, and the first kicks in as soon as the body detects a foreign intruder. White blood cells invade the site, causing inflammation which is responsible for chills, pain, fatigue, and other side effects.

This rapid response stage of your immune system tends to weaken as you age, one of the reasons young people report side effects more often than older adults. In addition, some vaccines simply cause more reactions than others.

However, everyone reacts differently. If you haven’t felt anything a day or two after either dose, that doesn’t mean the vaccine isn’t working.

Behind the scenes, the shots also set in motion the second part of your immune system, which will provide true protection against the virus by producing antibodies.

Another annoying side effect is that when the immune system is activated, it also sometimes causes temporary swelling of the lymph nodes, such as those under the arm. Women are encouraged to schedule routine mammograms before COVID-19 vaccination to prevent a swollen node from being mistaken for cancer.

Not all side effects are routine. But after hundreds of millions of doses of the vaccine administered around the world – and intense safety monitoring – few serious risks have been identified. A small percentage of people who have received vaccines made by AstraZeneca and Johnson & Johnson have reported an unusual type of blood clot. Some countries have reserved these injections for the elderly, but regulatory authorities say the benefits of offering them always outweigh the risks.

People also sometimes have severe allergic reactions. This is why you are asked to stay around 15 minutes after receiving any type of COVID-19 vaccine – to make sure any reaction can be treated quickly.

Finally, authorities are trying to determine whether the temporary heart inflammation that can occur with many types of infections could also be a rare side effect after mRNA vaccines, such as Pfizer and Moderna. U.S. health officials cannot yet say if there is a link, but say they are monitoring a small number of reports, mostly adolescents or young adults.

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The AP answers your questions about the coronavirus in this series. Submit them to: FactCheck@AP.org. Read more here:

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