COVID-19 vaccines cause the immune system to make antibodies to fight the COVID-19 virus.
The Food and Drug Administration (FDA) has given emergency use authorization to two types of COVID-19 vaccines. Coronaviruses have a spikelike structure on their surface called an S protein. Messenger RNA (mRNA) vaccines give your cells instructions to build a harmless piece of an S protein. Viral vector vaccines place genetic material from the COVID-19 virus into a modified version of a different virus. When this different virus enters your cells, it delivers genetic material from the COVID-19 virus that gives your cells instructions to make copies of the S protein. Both vaccines then cause the immune system to make antibodies to fight the COVID-19 virus.
More about how the COVID-19 vaccines work