The protection provided by two doses of a messenger RNA vaccine drops to less than 40% just a few months after the second dose1,2. But a third, ‘booster’ dose seems to help. One report found about 60–70% protection from infection at two weeks after a third shot1, and protection from severe illness seems strong.

https://www.nature.com/articles/d41586-022-00214-3?utm_source=pocket-newtab