In 2021 many people in the Netherlands will be vaccinated against COVID-19. The mass vaccination and the new types of vaccines trigger questions about the safety of these vaccines. In this paper we discuss: (1) what reactions are expected from COVID-19 vaccines, (2) what precautions are needed when vaccinating people, and (3) how to act when allergic reactions occur. The COVID-19 vaccines include the first vaccines produced with the mRNA platform. The most frequent adverse reactions are comparable with other vaccines. Allergic reactions to COVID-19 vaccines are rare but can occur. These reactions may be related to excipients in the vaccines, like polyethylene glycol. In case of a possible allergic reaction, a doctor, in consultation with an allergist, can investigate whether vaccination is safe in the future and whether precautions are necessary. Allergic reactions to vaccine components must be recorded completely and unambiguously in the patient file.