How long is vaccine effective for COVID-19?

New research finds that the mRNA vaccines from Moderna and Pfizer can lose effectiveness over time. However, the initial protection will vary from person to person. Recent research finds that protection from currently available mRNA vaccines declines a few months after vaccination.

Pfizer protection generally drops after 5 months but still more than 90 percent effective against it for around 4 months, after which it dropped to just 53 percent effectiveness at about 5 months after vaccination.

In one study reported by the Centers for Disease Control and Prevention (CDC), data from the state of New York showed vaccine effectiveness dropping from 91.8 to 75% against infection.

No one knows for sure whether one vaccine will last longer than another. Instead, one question to ask might be whether Pfizer and Moderna’s mRNA vaccines, which had an especially robust response, also have potential to be the longest lasting.

A study published in The New England Journal of Medicine found the Moderna vaccine to be 96.3% effective in preventing symptomatic illness in health care workers compared to 88.8% for Pfizer. Another study, from the CDC, found Moderna’s effectiveness against hospitalization held steady over a four-month period, while Pfizer’s fell from 91% to 77%. But scientists say more data is needed to fully understand the differences between the two vaccines.

 

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