Your Risk of COVID Is 10 Times Higher This Long After Vaccination, Study Says

Research has found that vaccines may lose some protective power over time.

At first, it seemed like vaccinations alone might be enough to end the COVID pandemic altogether. Over time, however, it's become clear that the virus won't go down without a fight. With high case rates across the country and minimal mitigation measures in place, everyone is at risk. While vaccinated people remain highly protected, there have still been thousands of breakthrough infections over the last few months. Research has found that the effectiveness of one or two vaccine doses might not be enough to combat certain factors, like the spread of the highly contagious Delta variant. But there could be another answer as to why the vaccines aren't quite as effective at preventing symptomatic infection as they were in clinical trials: time.

RELATED: If You're Vaccinated, This Is How Likely You Are to Get COVID, New Data Shows.

A new study from the Mayo Clinic looked at the long-term effectiveness of Pfizer's vaccine against over time. The researchers analyzed more than 97,000 patients who were fully vaccinated sometime in 2021, and tested at the Mayo Clinic for suspected symptomatic infection after vaccination. There were nearly 1,000 people with breakthrough cases included in the final analysis, which was preprinted Sept. 7 on medRxiv.

The Mayo Clinic researchers found that the risk of symptomatic infection increases with the amount of time that has passed after an individual's second shot. According to the study, the odds of developing a case with symptoms was seven times higher 120 days after full vaccination than immediately after your final dose. But by 150 days, or nearly five months, the risk of symptomatic infection was 10 times higher.

This doesn't mean the vaccines stop working, though. "Taken together, these data show that the risk of symptomatic infection several months after [Pfizer] vaccination is higher than at the date of full vaccination, but the risk of infection remains significantly lower than at a baseline or unvaccinated state, supporting public health recommendations for universal vaccination," the study authors concluded.

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According to the researchers, this study provides an "early signal for waning protection against symptomatic infection" from Pfizer's vaccine, which emphasizes the need for further investigation in how to prolong vaccine-induced immunity with reinstated restrictions or additional booster doses.

And it's not the first study to signal that Pfizer's vaccine protection might diminish over time. A U.K. study from August found that this vaccine's protection decreased to 74 percent five to six months after the second dose from 88 percent just a month after. Another study by Oxford researchers found that Pfizer's effectiveness may fall as soon as three months after full vaccination.

A Pfizer booster is already in the works. White House COVID adviser Anthony Fauci, MD, recently said that it was likely a Pfizer booster for the general public will be ready by Sept. 20. This is when the Biden administration has recommended that the U.S. start rolling out an additional shot for individuals who received their second dose eight months before, pending approval from public health officials.

"Looks like Pfizer has their data in, likely would meet the deadline," Fauci told CBS during Face the Nation on Sept. 5.

RELATED: The 5 Most Common Signs You Caught Delta If You're Vaccinated, Study Says.

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