A US study has found that COVID-19 antibodies produced by the Pfizer vaccine decreased sharply in aged care home residents and their caregivers six months after receiving their second shots.
David Canaday, a professor at the School of Medicine, and the research team – led by Case Western Reserve University in partnership with Brown University – studied blood samples of 120 Ohio nursing home residents and 92 health care workers. In particular, they looked at humoral immunity – also called antibody-mediated immunity – to measure the body’s defences against coronavirus.
The researchers, including a lab team at Harvard University, found that individuals’ antibody levels decreased more than 80% after six months; the results were the same in seniors (median age 76) and caregivers (median age 48) and old alike, according to the study.
Professor Canaday says the sharp decline was particularly problematic for seniors, because earlier research found that within two weeks of receiving the second dose of vaccine and being considered “fully vaccinated,” seniors who had not previously contracted COVID-19 already showed a reduced response in antibodies that was substantially lower than the younger caregivers experienced.
By six months after vaccination, the blood of 70% of these nursing home residents had “very poor ability to neutralize the coronavirus infection in laboratory experiments,” Prof Canaday said.
The results, Prof Canaday said, support recommendations for booster shots – especially for the elderly – due to fading immunity. He said that booster shots were even more important as the Delta variant spreads worldwide.