Some Vaccines Last a Lifetime. Here’s Why Covid-19 Shots Don’t.

Why don’t Covid-19 vaccinations last longer? Measles shots are good for life, chickenpox immunizations protect for 10 to 20 years, and tetanus jabs last a decade or more. But U.S. officials are weighing whether to authorize Covid-19 boosters for vaccinated adults as soon as six months after the initial inoculation. The goal of a vaccine is to provide the protection afforded by natural infection, but without the risk of serious illness or death. “A really good vaccine makes it so someone does not get infected even if they are exposed to the virus,” said Rustom Antia, a biology professor at Emory University who studies immune responses. “But not all vaccines are ideal.”