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COVID-19 Vaccination Plus Prior Infection Creates Long-Lasting Immunity

People infected with the virus that causes COVID-19 who later receive two doses of the Pfizer-BioNTech vaccine have elevated antibody levels that last at least 10 months, according to a new study by Cedars-Sinai investigators. The results are published in the journal BMJ Open

"This study adds to evidence that getting vaccinated even after having been infected with SARS-CoV-2, the virus that causes COVID-19, offers a benefit on top of natural immunity that lasts for some time," said Susan Cheng, MD, MPH, director of the Institute for Research on Healthy Aging in the Department of Cardiology at the Smidt Heart Institute at Cedars-Sinai and corresponding author of the study. 

It is important to understand what factors lead to greater or lesser COVID-19 immunity to guide decisions on who might need a booster shot and when, according to Cheng, the Erika J. Glazer Chair in Women's Cardiovascular Health and Population Science at Cedars-Sinai.

The study enrolled 843 healthcare workers between November 2020 and November 2021, prior to the emergence of the Omicron variant. The study participants provided blood samples, which the investigators used to measure levels of an antibody that recognizes a specific part of SARS-CoV-2 called the spike protein.

The measures showed almost all the participants had vaccine-induced anti-spike-protein antibody levels that remained positive 10 months after receiving two doses of the Pfizer-BioNTech vaccine. But those who had been previously infected with SARS-CoV-2 had antibody levels that were almost double the levels of those who had never been infected. 

Study participants who were female, age 42 or younger, or free of hypertension also had higher antibody levels than others.

"Recent studies found the protective response to SARS-CoV-2 can wane as early as three to six months after infection with the virus or vaccination without a booster," said Kimia Sobhani, PhD, director of Core Laboratories and associate professor of Pathology and Laboratory Medicine at Cedars-Sinai and senior author of the study. "These results help to show how immunity can be augmented and prolonged with vaccines and boosters. These data also point to what factors may play a role in driving that immunity."

The investigators plan to continue to track antibody levels in study participants for at least five years from the participants' vaccinations. 

"Time will tell how the extent and duration of a peron's antibody response protects against newer variants," Cheng said.

Other Cedars-Sinai investigators who worked on the study include Sandy Joung; Yunxian Liu, PhD; Min Wu, MPH; Patrick G. Botting, MSPH; Nancy Sun; Matthew Driver, MPH; Yu Hung Kao; Briana Khuu; Timothy Wynter; Trevor-Trung Nguyen; Helen S. Goodridge, PhD; Peter Chen, MD; Stanley C. Jordan, MD; Justyna Fert-Bober, PhD; Jennifer E. Van Eyk, PhD; Margo B. Minissian, PhD, RN; Moshe Arditi, MD; Gil Y. Melmed, MD; Jonathan G. Braun, MD, PhD; Dermot P. McGovern, MD, PhD. 

Funding: This study was funded by the Erika J. Glazer Family Foundation, F. Widjaja Family Foundation, Helmsley Charitable Trust (award number grants U54-AG065141) and the National Institutes of Health (award number K23-HL153888).