Why do I have muscle and headaches after vaccination?

It is true that fever and fatigue, for example, are a sign that the body is protecting itself. However, the symptoms usually come from a certain part of the immune system called the “innate immune system”.

It is the first to be activated after a vaccination and alerts the body to the potential danger of a foreign invader, says Peggy Riese, a vaccination specialist at the Helmholtz Infection Research Center in Braunschweig, Germany.

Immunology is a complex field. Simply put, there are two forms of immunity in humans, innate immunity and adaptive (acquired) immunity. When an infectious agent enters the human body, it is first and foremost innate immunity that is triggered within minutes or hours.

After vaccination, the vaccine is one such intervention for this part of the immune system. As such, he perceives not only the viral antigen that causes the protective effect, explains Ms. Riese, but also active ingredient enhancers or excipients such as stabilizers. This part of the immune system reacts immediately, but in a more general way.

Why some people are more prone to reactions to vaccination while others are not, is still not fully understood, according to the German specialist.

On the other hand, the specific protection against the pathogen Sars-CoV-2 is produced only over time by the cells of the “acquired” or “adaptive” immune system. In such an infection, the body learns how to form perfectly matched antibodies in the future and how to kill the cells of the body infected with specific T cells, such as killer cells.

Both types of immune system are involved in a very complex exchange between them, which has not yet been fully explored. In fact, the innate immune system vaccine response may provide the impetus for the acquired system to become active – but this impulse is often absent or barely noticeable.

“Even if you do not have side effects or only very mild effects such as mild injection site pain or headache, you are more likely to be protected as well as people who have stronger reactions to the vaccine injection such as fever, discomfort and pain. of the joints, ”says researcher Peggy Riese.

Symptoms after vaccination are not “an indication of the strength of vaccine protection,” confirms Christine Falk, president of the German Association of Immunology. People can be completely free of symptoms and still develop strong defenses. Conversely, in authorized studies of Covid 19 vaccines, people who received only one placebo also experienced symptoms.