COVID-19 Vaccines Offer Lasting Protection, Study Results Show

Vaccination offers long-lasting protection from the worst outcomes of COVID-19, according to the results of a new study.

Results of the study published in the New England Journal of Medicine suggest that declining immunity is responsible for breakthrough infections, but vaccines maintain protection from hospitalization and severe disease 9 months after getting the first shot.

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

“The primary takeaway message from our study is that unvaccinated people should get vaccinated right away,” Danyu Lin, PhD, Dennis Gillings Distinguished professor of biostatistics at the UNC Gillings School of Global Public Health, said in a statement. “The results of our study also underscore the importance of booster shots, especially for older adults.”.

The study, which is a collaboration between the North Carolina Department of Health and Human Service and the University of North Carolina at 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 CDC to support the use of booster shots.

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

The data included outcomes from cases caused by the Delta variant. However, the data were collected before the discovery of the omicron variant.

“Unlike previous studies, we estimated the vaccine effectiveness in reducing the current risks of COVID-19, hospitalization and death as a function of time elapsed since the first dose,” Lin said. “This information is critically important in determining the need for and the optimal timing of booster vaccination.”

The results showed that the effectiveness of the Pfizer and Moderna mRNA vaccines in reducing the risk of COVID-19 reached a peak of approximately 95% at 2 months after the first dose and then gradually declined.

At 7 months, the Pfizer vaccine dropped to approximately 67% effectiveness compared with the Moderna vaccine, which maintained approximately 80% effectiveness.

Among early recipients of the 2 mRNA vaccines, effectiveness dropped dramatically from mid-June to mid-July 2021, when the delta variant was surging.

Effectiveness for the Johnson and Johnson (J&J) vaccine was approximately 75% at 1 month after the injection and fell to approximately 60% after 5 months.

All 3 vaccines were effective at reducing hospitalizations related to severe COVID-19.

Effectiveness of the Pfizer vaccine reached a peak of approximately 96% at 2 months and remained at approximately 90% at 7 months, while the effectiveness of the Moderna vaccine reached a peak of approximately 97% at 2 months and remained at approximately 94% at 7 months.

Effectiveness of the J&J vaccine reached a peak of approximately 86% at 2 months and was higher than approximately 80% through 6 months.

All 3 vaccines were also more effective at preventing death than hospitalization.

“Because the majority of the vaccines in the United States were administered more than 7 months ago and only a small percentage of the population has received boosters, waning immunity is likely contributing to the breakthrough infections with the omicron variant,” Lin said.

Everyone aged 5 years and older is eligible for a COVID-19 vaccine.

Reference

Study shows COVID-19 vaccines offer lasting protection. EurekAlert. News release. January 12, 2022. Accessed January 14, 2022. https://www.eurekalert.org/news-releases/939989