Do measles vaccines work?

In an interview with Sean Hannity, HHS Secretary Robert Kennedy Jr. claims that the measles vaccine’s protection fades over time, doesn’t provide infants immunity from their mothers, and can cause severe side effects, suggesting that getting measles naturally might be safer and more effective.

This claim relies on thinking that getting measles naturally gives you stronger, lifelong protection, while the vaccine only gives weak immunity that fades away. But that’s not how immunity really works. When you get a vaccine, your body safely learns to recognize the virus without making you sick. Even if the protection from the vaccine weakens over time, your immune system still remembers the virus using special  memory cells. These memory cells usually remain in your body for your entire life, able to respond quickly and protect you from measles if you’re ever exposed.

This is why, in the current outbreak, the vast, vast majority of those infected with measles are unvaccinated (277 unvaccinated vs 2 vaccinated), despite most adults born after 1963 only receiving an MMR vaccine many years ago. Had protection actually waned, we’d see many more vaccinated people infected.

He also suggests that measles isn’t dangerous and that the case fatality rate is low. While acute fatality is around 1-3 in 1,000, death is not the only metric that makes measles dangerous. One in twenty will get pneumonia, and 1 in 5 unvaccinated people who get measles will be hospitalized.

The measles vaccine is both safe and effective, with millions of doses given annually.