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How long will COVID-19 vaccine immunity last?

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April 26, 2021—COVID-19 vaccines are among the best tools we have to end the pandemic. They teach the immune system to fight the virus. And we know these vaccines work very well.

What we don't know yet is just how long their protection will last.

It takes time to be sure

The vaccines are still new. And it's too early to tell how long immunity will last, the Centers for Disease Control and Prevention (CDC) reports. But scientists are actively studying people who were vaccinated in order to answer that question.

Here's what we know so far when it comes to the Pfizer and Moderna vaccines:

  • A recent study of the Pfizer vaccine found that it was 91.3% effective at preventing COVID-19 up to six months after the second dose. And at six months, it was still 100% effective at preventing severe COVID-19, as defined by CDC.
  • Interim results from Moderna's phase 3 clinical trial suggest that recipients of that vaccine also maintained a high level of protection up to six months after the second dose.

Keep in mind: These studies do not mean that COVID-19 vaccine protection fades after six months. It could last much longer than that. The vaccines just haven't been around long enough for us to know that yet.

We will learn more as scientists continue to follow people who were vaccinated. People who took part in the original vaccine clinical trials will be followed for up to two years. So time will tell.

We may need a booster shot

At some point, we may need booster shots to stay protected from COVID-19. Booster shots might also make the vaccines work better against any variants of the virus.

Vaccine makers are working to prepare for that possibility now.

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