We know that vaccines against Covid-19 can cause side effects that are sometimes significant, but generally mild. So theNational Agency for the Safety of Medicines and Health Products (ANSM) estimates that, since the start of the vaccination campaign against the SARS-CoV-2 coronavirus, 75% of the side effects reported were “not serious“.
Side effects after the Covid-19 vaccine: where do they come from? “There are two types of post-vaccination side effects: local side effects and the general side effects“, explains Pr. Michel Cogné, professor of immunology.
THE local side effectswe know them well: the arm that received the injection is painful, it may feel heavy and/or hot to the touch, it may be red…”These symptoms testify to local inflammation: following the injection, there is an influx of cells (white blood cells, leukocytes, macrophages, etc.) which come to fight against what the body interprets as an infection.develops Prof. Michel Cogné. This is a normal, and even desired, immune reaction.“
THE general side effects (fever, headaches, fatigue…) are less frequent,”and the mechanism that leads to their occurrence is still poorly understood.“says the specialist.
To know. “The absence or discretion of side effects is the most common situation (we never talk about trains arriving on time!)notes Prof. Michel Cogné. Truly bothersome side effects of vaccination only affect about 1 in 1000 patients, and local effects are commonplace.“
No link between the intensity of side effects and the quality of antibodies
I had no side effects after my vaccination, am I protected? “Yes !“says Pr. Michel Cogné from the outset. “Several studies have been conducted on the issue, and they are clear: there is no link between the intensity of post-vaccination side effects and the quality of the antibodies against the SARS-CoV-2 coronavirus produced.“
So, a Japanese study published at the end of July 2021 (conducted on a group of 225 healthy volunteers, who received 2 doses of messenger RNA vaccine in February 2021) states: “the immune response elicited by the vaccine cannot be significantly associated with the magnitude of side effects experienced by vaccinees“.
Why do some people have side effects after vaccination? “This is a parameter specific to each person: some people will tend to respond “noisily” to infections while others will have almost no symptoms. It does not change the quality of the immune response“says Pr. Cogné.
“The same phenomenon is observed with mosquito bites: while some people will have no symptoms, not even itching, others will see their skin swell, become red and hot, etc. This is part of the “personality” of each organization.“
To know. “It is not yet known which people are most likely to experience side effects after vaccination against Covid-19remarks the specialist. The only thing we can say is that people who had side effects (significant or not) at the first dose have an increased risk of having them at the second dose.“
Thanks to Pr. Michel Cogné, professor of immunology at the University Hospital of Rennes.
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