People who are fully vaccinated with the Pfizer BioNTech two-dose vaccine should still practice mitigation efforts if they do not want to get infected with COVID-19, according to two recent studies.
Soon after the second dose, the Pfizer vaccine is around 94 to 95 percent effective against infection. Both studies, published in the New England Journal of Medicine, found that the vaccine is less effective over time, though it consistently protects against severe infection, hospitalization and death.
One six-month study was conducted by Israeli researchers from last December through this July involving 4,868 vaccinated health care workers who were tested monthly for the presence of certain antibodies. Researchers found that protection from the vaccine “substantially decreased, especially among men, among persons 65 years of age or older, and among persons with immunosuppression,” during the six-month period.
Immunity lasted longer in people who were vaccinated after natural COVID-19 infection, according US News & World Report.
Researchers in Qatar found that “protection against infection builds rapidly after the first dose, peaks in the first month after the second dose, and then gradually wanes in subsequent months,” according to the other study of Pfizer’s vaccine.
Study authors said that this waning efficacy could be tied to vaccinated people dropping mitigations that add extra protection against COVID-19 infection.
“Vaccinated persons presumably have a higher rate of social contact than unvaccinated persons and may also have lower adherence to safety measures,” they wrote. “This behavior could reduce real-world effectiveness of the vaccine as compared with its biologic effectiveness, possibly explaining the waning of protection.”
Overall, U.S. News & World Report said the Pfizer vaccine’s effectiveness wears off after two months, while it maintains protection against severe infection.
Last month, the U.S. Food & Drug Administration approved Pfizer’s booster shot – to be administered six months after the second dose of the vaccine – for vulnerable populations, including people over 65 years old and people with high-risk conditions.
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