Vaccines are tested to prove they are safe and effective. Safe means it won’t make you sick. Effective means that it really protects you from the disease. Tests often run into issues. On September 8, one trial was paused because a participant developed a serious illness. If doctors find the illness is unrelated, tests will continue. This is why tests are so important and can’t be rushed.

US FDA: Vaccines

US FDA: Ensuring the Safety of Vaccines in the United States

Reuters: AstraZeneca suspends leading COVID-19 vaccine trials after a participant’s illness

STAT: AstraZeneca Covid-19 vaccine study put on hold due to suspected adverse reaction in participant in the U.K.