Post-vaccination fever may be the result of the immune system responding to an administered antigen. For most of us, fever is associated primarily with the symptom of a disease and if it occurs, it can cause us anxiety. However, fever is also one of the most common reactions to immunization. When does post-vaccination fever appear and can it be dangerous?

Feveris a rise in body temperature above normal (usually assumed to be 36.6 ° C) and usually results from a complex response by our immune system. It is worth emphasizing that fever is not a disease, but a physiological response of the body to the presence of substances that induce the production of biochemical molecules - cytokines. These molecules, in turn, affect the activity of the hypothalamus neurons and the central thermoregulation center, causing an increase in body temperature.

Fever as a physiological response

The exact role of fever as a physiological response remains an unresolved question. There are several hypotheses about this.

One of them explains that during a fever the body becomes a less friendly environment for pathogenic microorganisms, which limits their ability to multiply.

Another postulates that increased temperature leads to the activation of various biochemical pathways that coordinate the immune response.

Fever should be differentiated from hyperthermia , a condition that usually results from insufficient heat elimination as a result of excessive heat production (e.g. intense exercise) or exposure to heat (e.g. sun) ).

During hyperthermia, the body temperature may rise very high (40-42 ° C) and the body overheats. For this reason, it is an extremely dangerous condition as it can lead to brain damage if left untreated.

Rush - breakdown

Fever can be divided according to the amount of temperature:

  • 37-38 ° C - low fever
  • 38-38.5 ° C - low fever
  • 38.5-39 ° C - moderate fever
  • 39-40 ° C - high fever
  • above 40 ° C - hyperpyrexia

Fever - causes

The formation of fever is initiated by the so-called pyrogens. We divide pyrogens into endogenouse.g. pro-inflammatory or exogenous cytokines, which include a number of factors:

  • viruses,
  • bacteria,
  • parasites,
  • allergic reactions,
  • certain chronic diseases, e.g. rheumatoid arthritis or ulcerative colitis,
  • malignant neoplasms,
  • drugs, e.g. immunosuppressants or antibiotics
  • stress and high emotions.

In addition,fever is a commonly reported symptom after vaccination .

Post-vaccination fever - when can it occur?

In most casespost-vaccination fever occurs within 24 hours and resolves within 2-3 days , usually below 38 ° C.

With some vaccines , such as measles, mumps and rubellapost-vaccination fever may take up to 1-2 weeks.

Post-vaccination fever - what does it mean and is it dangerous?

The vaccine is designed to prepare our immune system to protect against pathogens that cause human disease. Although vaccines are not harmful to our he alth, they can (and should) activate the immune system to induce permanent immunity, but without the development of disease.

The vaccine is designed to mimic a natural infection with a given pathogen, and therefore some people may develop a slight fever after vaccination.

Additionally, some vaccines require more than one dose to be effective. Then a post-vaccination fever may be more likely with your next doses.

It must be borne in mind that sometimes an infection with e.g. cold viruses can occur immediately after vaccination. Then the fever may be due to an infection and not from the vaccination itself. Therefore, if a fever after vaccination lasts longer than 3 days, you should consult your primary care physician and look for its cause.

Post vaccination fever - what to do?

Our first reflex when a fever appears after vaccination is to use antipyretic drugs such as ibuprofen or paracetamol. However, will this not affect the effectiveness of the vaccination used?

It turns outThe World He alth Organization (WHO) does not recommend taking painkillers such as acetaminophen, for example before receiving the COVID-19 vaccine, to prevent side effects.

These recommendations are based on the fact that painkillers have the potential to develop immunity to vaccines. However, after the vaccination itself, e.g. when a fever occurs, according to WHO, such drugs can be taken.

Despite this, many experts emphasize that even after vaccination, if it is possible, of course, we should refrain from taking antipyretic drugs. What we can do and will not affect the effectiveness of vaccination is adequate hydration during a fever and rest . It is also worth avoiding very intense physical exertion and stress.

  • NOP - unwanted vaccine reaction. What is an NOP and where to report it?
  • Vaccinations and vaccines: types, action, post-vaccination reaction

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