U.S. Study Shows COVID-19 Vaccines Offer Lasting Protection

Vaccination offers long-lasting protection from the worst outcomes of COVID-19, according to a new study by the University of North Carolina at Chapel Hill, ScienceDaily reported.

Photo Insert: The results of the study underscore the importance of booster shots.

The emergence of the delta and omicron variants has raised questions about whether breakthrough infections are caused by waning immunity or by the more transmissible variants.

Results of the study published in the New England Journal of Medicine suggest that declining immunity is responsible for breakthrough infections, but vaccines maintained protection from hospitalization and severe disease nine months after getting the first shot.

"The primary takeaway message from our study is that unvaccinated people should get vaccinated right away," said lead study author Dr. Danyu Lin, Dennis Gillings Distinguished Professor of Biostatistics at the UNC Gillings School of Global Public Health.

"The results of our study also underscore the importance of booster shots, especially for older adults." The study, which is a collaboration between the UNC-Chapel Hill and the North Carolina Department of Health and Human Services, examined data on COVID-19 vaccination history and health outcomes for 10.6 million North Carolina residents between December 2020 and September 2021. The study results were used by the Centers for Disease Control and Prevention to support the use of booster shots.

The study found that the effectiveness of the Pfizer and Moderna mRNA vaccines in reducing the risk of COVID-19 reached a peak of about 95% at two months after the first dose and then gradually declined. At seven months, the Pfizer vaccine dropped to 67% effectiveness, compared to the Moderna vaccine, which maintained 80% effectiveness.

Effectiveness for the Johnson & Johnson adenovirus vaccine was 75% at one month after injection and fell to 60% after five months. All three vaccines were effective at keeping people out of the hospital due to severe COVID-19.

Effectiveness of the Pfizer vaccine reached a peak of 96% at two months and remained around 90% at seven months; effectiveness of the Moderna vaccine reached a peak of 97% at two months and remained at 94% at seven months. Effectiveness of the Johnson & Johnson vaccine reached a peak of 86% at two months and was higher than 80% through six months.

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