Vaccination against COVID-19 is the single most effective way to reduce severe illness and death from infection. Two COVID-19 vaccines are currently in use in Australia – AstraZeneca and Comirnaty (Pfizer). Like all medicines, the vaccines can have side effects (also known as adverse events). The overwhelming majority of these are mild and resolve within a few days. The Therapeutic Goods Administration (TGA) closely monitors suspected side effects. Importantly, adverse events reported to the TGA are often not caused by the vaccine itself. Learn more about causality.