Basic concepts of contraindications for the COVID-19 vaccine. The effectiveness and safety of the COVID-19 vaccine against the human immune system have been verified in large-scale clinical trials. However, before taking the vaccine, you also need to know the contraindications of the COVID-19 vaccine. Contraindications are specific conditions in which vaccination would cause adverse reactions or worsen the recipient\’s health. There are many contraindications to the COVID-19 vaccine, which can lead to serious consequences once vaccinated. Therefore, it is important to understand before receiving the COVID-19 vaccine.