Gillings School of Global Public Health research suggests boosters may provide ongoing prevention of hospitalization and death
Vaccination offers lasting protection against the worst outcomes of COVID-19, according to a new study from the University of North Carolina at Chapel Hill.
The emergence of the delta and omicron variants has raised questions about whether progressive infections are caused by waning immunity or more transmissible variants.
Study results published in the New England Journal of Medicine suggest that waning immunity is responsible for progressive infections, but the vaccines maintained protection against hospitalization and severe disease nine months after receiving the first shot.
"The main takeaway message from our study is that unvaccinated people should get vaccinated immediately"
said the study’s lead author, Danyu Lin, PhD, 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 vaccinations, especially for older adults.”
The study, which is a collaboration between UNC-Chapel Hill and the North Carolina Department of Health and Human Services, examined data on the COVID-19 vaccination history and health outcomes of 10.6 million North Carolina residents. North Carolina 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 vaccines.
“This is an excellent example of the wonderful research partnership between the Gillings School and NCDHHS, who are working together to generate the evidence base necessary to keep our communities safe,” said Penny Gordon-Larsen, PhD, Carla Distinguished Professor Smith Chamblee of Global Nutrition and associate dean for research at the UNC Gillings School of Global Public Health
This data included the results of COVID-19 cases caused by the delta variant. However, the data for this study was collected before the discovery of the omicron variant.
“By applying novel methodology to rich surveillance data, we were able to provide an accurate and comprehensive characterization of effectiveness over a nine-month period for the three vaccines used in the US,” Lin said.
“Unlike previous studies, we estimated the effectiveness of the vaccine in reducing the current risks of COVID-19, hospitalization and death based on the time since the first dose,” Lin continued. “This information is vitally important to determine the need and optimal timing of booster vaccination.”
The study found that the effectiveness of the Pfizer and Moderna mRNA vaccines in reducing the risk of COVID-19 peaked at about 95% two months after the first dose and then gradually declined. At seven months, the Pfizer vaccine dropped to 67% effective, compared to the Moderna vaccine, which remained 80% effective.
Among early recipients of the two mRNA vaccines, efficacy dropped sharply from mid-June to mid-July, when the delta variant was surging.
The efficacy of the Johnson & Johnson adenovirus vaccine was 75% one month after injection and fell to 60% after five months.
All three vaccines were effective in keeping people out of the hospital due to severe COVID-19.
Vaccine effectiveness against symptomatic Covid-19 and related hospitalization and death in England. Vaccine efficacy was assessed among people aged 16 years and older who had received two doses of the ChAdOx1-S or BNT162b2 vaccine in England. Data are shown on the effectiveness of the vaccine against infection with the B.1.1.7 (alpha) and B.1.617.2 (delta) variants, based on the time since the second dose of the vaccine. There were not enough cases of infection with the alpha variant in the post-vaccination periods, as the alpha variant had largely disappeared in the UK at this stage. The numbers were too small for assessment of death within 1 week. �� bars indicate 95% confidence intervals. Covid-19 denotes coronavirus disease 2019.
The efficacy of the Pfizer vaccine peaked at 96% at two months and remained around 90% at seven months; The Moderna vaccine’s efficacy peaked at 97% at two months and remained at 94% at seven months. The efficacy of the Johnson & Johnson vaccine peaked at 86% at two months and was over 80% at six months.
For all three vaccines, the effectiveness against death was greater than that against hospitalization.
“Because most vaccines in the US were administered more than seven months ago and only a small percentage of the population received boosters, waning immunity is likely contributing to the advancement of infections with the variant omicron,” Lin said.
Everyone over the age of 5 is eligible for a COVID-19 vaccine. Those over 18 years of age should receive a booster vaccine. Visit the NC DHHS website to find a vaccination clinic near you.
The research was led by Lin with major contributions from Yu Gu, PhD student in biostatistics, and Donglin Zeng, PhD, professor of biostatistics. NCDHHS epidemiologists Bradford Wheeler, Hayley Young, Shadia Khan Sunny and Zack Moore participated in the research. Shannon Holloway of the North Carolina State Department of Statistics also contributed.
