The protection that fully vaccinated Americans have against COVID-19 infection severely drops over time, a new study suggests.
A team led by the Public Health Institute in Oakland, California, found that the overall effectiveness of the three Covid vaccines available in the U.S fell from 87 percent in March to 48 percent by September.
Johnson & Johnson vaccine recipients are especially at risk with just 13 percent efficacy against contracting the virus.
However researchers found that the shots are still highly protective against death from Covid.
The combined effectiveness of the COVID-19 vaccines has dropped below 50% as of September. The J&J vaccine is the least effective, only reducing risk of infection by 13%. Pfizer's shot reduces risk of infection by 43% and the Moderna by 58%
While the vaccines are not as effective at preventing infection from Covid anymore, they still reduce a person's risk of death from the virus. Researchers found that it can reduce likelihood of death for a person under 65from 2.6% to 1.6% (left). The shots reduce risk of death for people over 65 from over 20% to 9% (right)
Researchers, who published their findings on Thursday in the journal Science, gathered data from the Veterans Health Administration from February to October 2021.
In total, nearly 800,000 veterans' data was included in the massive study.
The team analyzed vaccine records among people who tested positive for the virus, and determined, on average, how effective each individual jab was at preventing infection.
In February, when the vaccines were still relatively new, they all had an effectiveness of more than 85 percent at preventing infection.
J&J's vaccine saw its protection wane the most, dropping from 86 percent in March to below 50 percent by September, and down to only 13 percent last month.
The Pfizer-BioNTech jab - which is far and away the most commonly used in the U.S. - saw its effectiveness drop from 87 percent in March to 43 percent in September.
September was the first month during which the effectiveness of Pfizer's vaccine dropped below 50 percent.
Moderna's shot held up the best, and is the only one of the three to still be more than 50 percent effective.
The shot's effectiveness
