Why do some people get side effects after COVID-19 vaccines?
Temporary side effects, including headache, fatigue and fever, are signs that the immune system is reviving – a normal response to vaccines. And they are common.
“The day after receiving these vaccines, I would not plan anything that would be intense physical activity,” said Dr. Peter Marx, head of the US Food and Drug Administration, who is tired after his first dose.
Here’s what happens: The immune system has two main arms, and the first begins as soon as the body detects a foreign intruder. White blood cells swarm to the site, causing inflammation, which is responsible for chills, soreness, fatigue and other side effects.
This step of rapid response of your immune system tends to weaken with age, one of the reasons younger people report side effects more often than older people. Also, some vaccines simply cause more reactions than others.
However, everyone reacts differently. If you do not feel anything a day or two after the dose, this does not mean that the vaccine is not working.
Behind the scenes, the shots trigger the second part of your immune system, which will provide real protection against the virus by producing antibodies.
Another unpleasant side effect: As the immune system is activated, it sometimes causes temporary swelling of the lymph nodes, such as those under the armpit. Women are encouraged to schedule routine mammograms before vaccination against COVID-1
Not all side effects are routine. But after hundreds of millions of doses of vaccines have been administered worldwide – and intensive safety monitoring – few serious risks have been identified. A small percentage of people who received vaccines made from AstraZeneca and Johnson & Johnson reported an unusual type of blood clot. Some countries have kept these photos for older people, but regulators say the benefits of offering them still outweigh the risks.
People occasionally have serious allergic reactions. Therefore, you are required to stay for about 15 minutes after receiving any type of COVID-19 vaccine – to ensure that any reaction can be treated immediately.
Finally, authorities are trying to determine whether temporary heart inflammation, which can occur with many types of infections, can also be a rare side effect after mRNA vaccines made by Pfizer and Moderna. U.S. health officials are still unable to say if there is a connection, but say they are seeing a small number of reports, mostly from teenage men or young adults.
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