Adults infected with COVID-19 develop circulating antibodies that last for nearly 500 days, according to a new study led by researchers at UTHealth School of Public Health.

The findings were published in The Journal of Infectious Diseases.

Researchers examined data from over 57,000 volunteers across the state of Texas over the age of 20 who were enrolled in the Texas CARES survey, which began in October of 2020 with the goal of assessing COVID-19 antibody status over time among a population of adults and children in Texas.

“These results are promising because we now have a good estimate of how long antibodies last after a COVID-19 infection,” said Michael Swartz, PhD, associate professor and vice chair of biostatistics at UTHealth School of Public Health and corresponding author on the study. “Our research shows that the level of antibodies in those previously infected increases for the first 100 days post-infection and then gradually declines over the next 500 days and beyond.”

Researchers used blood draw samples from Oct. 1, 2020, to Sept. 17, 2021. Most volunteers self-reported a COVID-19 infection before October of 2020. The results differed from person to person based on their age, body mass index (BMI), smoking or vaping use, and the severity of infection; however, all volunteers showed a similar decrease in antibodies.

The results of this study are just another step in understanding the virus’s impact, and although antibodies after infection can last for almost a year and half, Swartz says it’s important to understand that being vaccinated against the virus offers the best protection against infection, reinfection, or hospitalization.

“Vaccines are a great source of protection. We know that the rates of reinfection or hospitalization after being vaccinated are a lot lower than not being vaccinated, especially against other variants like we saw with Delta and Omicron. So, if you haven’t been vaccinated, now is the time to do it,” Swartz said. 

Previous research out of Texas CARES found children previously infected with COVID-19 had circulating antibodies that lasted for at least seven months.

The Texas CARES program is still ongoing. To learn more about how to get involved, visit https://sph.uth.edu/projects/texascares/.

Additional UTHealth Houston authors include: Eric Boerwinkle, PhD; Stacia M. DeSantis, PhD; Ashraf Yaseen, PhD; Frances A. Brito, MS; Melissa A. Valerio-Shewmaker, PhD, MPH; Sarah E. Messiah, PhD, MPH; Luis G. Leon-Novelo, PhD; Harold W. Kohl III, PhD, MSPH; Cesar L. Pinzon-Gomez, MD; Tianyao Hao, MS; Shiming Zhang, MS; Yashar Talebi, MS; Joy Yoo, BS; Jessica R. Ross, BS; Michael O. Gonzalez, MS; Leqing Wu, PhD; and Steven H. Kelder, PhD, MPH. Other authors include Mark Silberman, MD, and Samantha Tuzo, BS, with Clinical Pathology Laboratories; Jennifer A. Shuford, MD, MPH, and Stephen J. Pont, MD, MPH, with the Texas Department of State Health Services; and David Lakey, MD, with The University of Texas System.

Funding for Texas CARES was provided by the Texas Department of State Health Services (Contract #HHS000866600001).