Protection against symptomatic COVID-19 begins to decline one month after initial vaccination, while immunity to severe COVID-19 remains high for about six months, according to a new study.

For the study, researchers analyzed data from 7 million unvaccinated and vaccinated people. The latter received doses of the COVID-19 vaccine from Pfizer-BioNTech, Moderna or Johnson & Johnson. Conducting a systematic review and meta-analysis, the researchers examined 18 peer-reviewed studies published from December 2019 to November 2021, before the advent of Omicron option which dominates the most recent increase in the U.S. pandemic.

According to the Centers for Disease Control and Prevention, more than 577 million doses of COVID-19 vaccine have been administered nationwide. Vaccinated people may wonder how long the vaccine provides protection against the coronavirus.

Research has shown that vaccines provide significant protection against COVID-19, but their effectiveness has declined over time. After complete vaccination, immunity to COVID-19 infection decreased from 83% after the first month to 22% after five or more months.

The study includes data on adults and children 12 years of age and older. The results show that recipients of the Moderna vaccine had the highest levels of protection.

Fully vaccinated people are defined as those who have received two doses of Moderna or Pfizer vaccines, as well as people who have received one dose of Johnson & Johnson vaccine. The researchers had no data for more than six months, and the study did not include data on booster vaccines.

“It is reassuring to see that individuals vaccinated against COVID-19 maintain strong protection against hospitalization and death over time, even as efficacy against infection declines,” said senior author Catherine Pauls, an assistant professor in the Penn State Department of Medicine. “More data specific to protection against the Omicron variant is needed.”

Researchers say vaccines remain 90% effective against heavy COVID up to six months. However, protection against severe COVID-19 is lower (74%) for people who have received the Johnson & Johnson vaccine. According to the study, immunity to COVID-19 decreases faster in humans 65 or moreregardless of which vaccine they received.

“It is important to note that the rate of reduction in the effectiveness of the COVID-19 vaccine is not the same. Adult populations had a higher rate of declining efficiency, “said Paddy Sentongo, an assistant professor in the Department of Public Health and lead author of the study. BMC Infectious Diseases.

“Future research should focus on showing how vaccine protection continues in various comorbidities and immune suppression status.

Researchers note that overall efficacy may depend on several factors, including vaccine type, patient age, emerging options, and geographic areas. According to the CDC, subsequent doses of the vaccine are recommended over time to help boost immunity and mitigate the threat of COVID-19. The evidence shows this booster dose may provide a short-term increase in protection against COVID-19 infection and symptomatic disease.

“COVID-19 vaccines are crucial to ending the pandemic, and even if their effectiveness against infection decreases, they provide key and important protection against severe COVID-19 disease, which can lead to hospitalization,” Ssentongo said. “Future studies will need to examine the evolution of efficacy against Omicron and hospitalizations associated with newer options.

The authors note that a high degree of variation in factors such as study design, follow-up duration, geographic location, vaccine types, and virus variants may have influenced the results.

Researchers do not declare a conflict of interest or specific funding for this study.

Source: Penn State

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