The efficacy of messenger RNA vaccines Pfizer and Modern decreases after four months to prevent symptomatic SARS-CoV-2 virus infection, study suggests.
While these antigens have previously shown 95 and 94.1 efficacy rates percent, respectively, in initial clinical trials, this decreases slightly to 84 percent after the second dose.
In the study, published in the New England Journal of Medicine, a COVID outbreak occurred in healthcare workers fully vaccinated with mRNA antigens from the University of California San Diego Health.
From March 1 to July 31, 2021, a total of 227 health workers from that place tested positive for the SARS-CoV-2 virus, of which 130 were fully vaccinated. Among the infections, positive cases were found: Delta variant.
Symptoms were present in 109 of the 130 fully vaccinated workers and in 80 of the 90 non-inoculated workers. No deaths were reported in either group and only one unvaccinated person was hospitalized for symptoms related to the virus.
The effectiveness of the vaccine was calculated for each month from March to July. Antigen was found to exceed 90 percent from March to June, but fell to 65.5 percent in July.
“Our data suggest that the effectiveness of the vaccine against any symptomatic disease is considerably lower against the variant Delta and it can decrease over time after vaccination, ”the researchers noted.
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