Study Finds Nursing Home Residents Have Lower Vaccine Immune Response

A COVID-19 vaccine administered to nursing home residents in northeast Ohio was less effective in creating an antibody response in them than in a control group of health care workers, according to a Case Western Reserve-led study.

Some residents responded "reasonably well," but a portion responded "poorly to very poorly," concluded university researchers.

What's not yet clear is why, or what the threshold for protection is when measured in terms of antibodies.

"We urgently need better longitudinal evidence on vaccine effectiveness" to inform best practices for nursing home infection control measures, outbreak prevention and potential indication for a vaccine boost, stated the study.

Its co-principal investigators include David Canaday, MD, a professor in the School of Medicine’s Division of Infectious Disease, and Mark Cameron, PhD, an associate professor in the school’s Department of Population and Quantitative Health Sciences.

Preliminary results were released online in late March.

Once COVID-19 reached the United States, nursing homes became hotspots, with a rapid rise of infections and deaths; when vaccines became available, nursing home residents were among the first to receive them.

The study focused on the antibody immune response in residents by comparing a blood sample taken before the first vaccination, with another taken about two weeks after the second one.

It included 149 residents and a younger control group of 110 health care workers. All participants received the Pfizer vaccine.

Researchers examined three measures of antibodies; in all cases, residents had lower levels. For example, residents had a quarter of the anti-virus antibodies as the control group.

Canaday said the study's results can’t be compared to Pfizer’s vaccine efficacy rate of 95% because the Pfizer clinical trial focused on the number of adults of any age who got COVID-19, not the quantity of antibodies in the blood.

"The vaccine does make an immune response in almost every nursing home resident, although the magnitude is lower than in the younger age," Canaday said.

The study was the first outcome from a $2.3 million National Institutes of Health grant focused on COVID-19's spread in nursing homes awarded to Canaday, Cameron and fellow co-principal investigator Stefan Gravenstein, MD, a geriatrician and professor at Brown University.

They are now exploring varying responses to COVID-19 in nursing home residents and what level of antibodies is protective.

"There are so many questions to be answered surrounding the role of one's immune system in determining whether an infected individual has a mild, moderate or very severe form of COVID-19," Cameron said, "especially in people who are older or have underlying health issues that put them more at risk for poor outcomes."