Moderna Inc. has released a new study that shows people who got its vaccine last year are twice as likely to have a breakthrough infection than those who got the vaccine more recently.
88 people who got the vaccine between January and March of 2021 had a breakthrough infection, compared to 162 people who got the vaccine between July and December 2020.
Severe infections were also twice as numerous among those who were vaccinated earlier, with 13 severe infections in the earlier group and only six when they were vaccinated this year.
Breakthrough cases are those that occur more than 14 days after receiving a second dose of the shot.
The findings show that immunity to infection, including severe infection, seems to decline over time, which may show the need for booster shots at some point.
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