the first study of its kind shows.
“It is well known that patients on dialysis may have a reduced response to vaccination,” Ayelet Grupper, MD, of Tel Aviv Medical Center, and colleagues observe. Their study was published online April 6 in the Clinical Journal of the American Society of Nephrology.
“I believe our findings should encourage patients with kidney failure treated with dialysis to be vaccinated as soon as vaccination becomes available for them, while we as caregivers should explore ways to enhance its efficacy in our patients,” senior author Moshe Shashar, MD, noted in a statement from the American Society of Nephrology.
Asked to comment, Peter Blake, MD, professor of medicine, University of Western Ontario, London, pointed out that COVID-19 is very common among hemodialysis patients and that the likelihood of these patients dying from it is very high. Indeed, 1.5% of approximately 12,500 patients receiving dialysis in the province of Ontario have died of COVID-19 – “a horrifying statistic and one that only long-term care home residents can compare with,” he told this news organization.
In the Israeli study, almost all dialysis patients mounted a serologic response to the Pfizer-BioNTech vaccine, which is “good news” overall, Dr. Blake said.
Also commenting on the study, Anushree Shirali, MD, of Yale University, New Haven, Conn., said she was impressed by the fact that most of the dialysis patients in the study mounted at least some IgG response to vaccination, which she said was good “in and of itself,” because that is not always the case with other vaccines.
Study compared dialysis patients with health care workers
The Israeli study included 56 patients who were receiving maintenance hemodialysis and 95 health care workers, who served as control persons.
“All participants had been previously vaccinated with the [Pfizer-BioNTech] vaccine, with the recommended dosing interval of 21 days between the first and second doses,” the investigators note. Immunogenicity was assessed using a dedicated immunoassay to quantify the level of IgG antibodies from participants’ plasma.
A cutoff for a positive antibody response was greater than or equal to 50 arbitrary units per milliliter (AU/mL). “All subjects in the control group developed a positive antibody response (≥50 AU/mL) as compared with 96% (54 of 56) in the dialysis group,” Dr. Shashar and colleagues report.
The median IgG level in the dialysis group was 2,900 AU/mL, which is significantly lower than the median of 7,401 AU/mL in the control group (P < .001), they report.
The investigators also observed a significant inverse correlation between older age and antibody levels in both groups.
The odds of being in the lower quartile were significantly higher for older individuals (odds ratio, 1.11 per year of age; P = .004) and for the dialysis group compared with the control group (OR, 2.7; P = .05).
Among the dialysis patients, older age and lower lymphocyte count were associated with antibody response in the lower quartile (OR, 1.22 per 1 year older; P = .03; and OR, 0.83 per 10-e3/mL-higher lymphocyte count; P = .05).
Among recipients older than 70 years, there was little difference in antibody response between the dialysis patients and the control group. Thus, age is clearly an important contributor to a robust humoral response, the authors observe.
For more than 90% of the patients receiving dialysis, the antibody response was well above 50 AU/mL, which was the cutoff for having a positive response.
Nevertheless, the authors suggest that their findings should prompt clinicians to consider either changing the dose or the schedule of COVID-19 vaccination for dialysis patients, as was done, for example, with the hepatitis B vaccine Engerix-B.
Dialysis patients now receive double doses of the hepatitis B vaccine, which is given in a four-series vaccine schedule rather than a three-series vaccine schedule, as is given to healthy individuals.
The authors also call for studies to assess the longevity of vaccine efficacy for dialysis patients and whether current vaccines are effective against variant strains among patients undergoing dialysis.