A side effect is an undesired effect of a medicinal product or vaccine. Examples of side effects include a mild fever or a sore arm. In addition, the injection site may be a bit red or swollen. Small children can also become listless or tearful. These side effects are generally mild and go away on their own within a few days. Serious side effects are very rare.

Side effects are constantly being studied. That is why we are aware of most of the side effects related to vaccines. Read more on the page about research on side effects, or on the website of the Pharmacovigilance Centre Lareb. Are you unsure about whether you want to have your child vaccinated, because of the possible side effects? Check out the page on doubts about vaccination.