Patients on maintenance dialysis had somewhat higher rates of SARS-CoV-2 infections and related deaths than seen in the general U.S. population, although immunization mitigated some of the excess risk, the CDC reported.

From June 30, 2021, to Sept. 27, 2022, the overall infection rate per 10,000 patient-weeks was 30.47 among maintenance dialysis patients, with a range from 20.13-46.45 across the different waves of variants compared with 17.13-43.62 per 10,000 population-weeks in the general population.

The overall COVID-19 death rate was 1.74 per 10,000 patient-weeks in dialysis patients, with a range of 0.59-2.66 across variant waves compared with 0.06-0.26 in the general population, Jose Navarrete, MD, of the CDC in Atlanta, and colleagues reported in the Morbidity and Mortality Weekly Report.

That mortality rate in the dialysis patients is higher than for people over age 75 in the general U.S. population, the group at highest risk for death from the virus, according to the researchers.

While both the infection and death rates among dialyzed patients were higher at all time points than those among the general population, the mRNA COVID-19 vaccines did improve patient outcomes when it came to infection rates, the team noted. (A limitation of the study was that death by vaccination status in the dialysis group was not available for analysis.)

Infection rates among the dialysis patients who received a complete primary COVID-19 vaccination series was lower compared with unvaccinated dialysis patients (27.24 vs 39.64 per 10,000 patient-weeks), Navarrete and co-authors reported. During the first and second Omicron waves, the overall infection rate among dialysis patients who had received at least one monovalent booster dose was 30.62, compared with 33.69 among vaccinated patients who had not received a monovalent booster dose.

The benefit of vaccination appeared to wane in dialyzed patients as the pandemic wore on, the investigators said. There were no differences in infection rate between the vaccinated and unvaccinated patients during the second Omicron wave – possibly because of lower overall infection rates, declining vaccine effectiveness, and the emergence of new variants. Nevertheless, the vaccine was well-tolerated and did exert a protective effect on this immune-compromised population.

“Although formal studies of vaccine effectiveness have not been conducted in this population, data suggest that receipt of a two-dose primary mRNA COVID-19 vaccination series is protective in dialysis patients despite their having a slightly attenuated immune response,” the researchers wrote.

One of the implications is boosting vaccine coverage, they suggested, noting that approximately 70% of dialysis patients have completed a primary vaccination series, but only 54% received additional primary or booster doses.

“The reported side effects of SARS-CoV-2 vaccination did not differ between dialysis patients and persons not receiving dialysis,” they noted.

The analysis employed data from CDC’s National Healthcare Safety Network (NHSN). That network collects weekly data on healthcare-associated infections occurring in acute care and critical access hospitals, long-term care facilities, ambulatory surgery centers, inpatient psychiatric and rehabilitation facilities, and dialysis centers. Since November 2020, NHSN has been collecting weekly data on SARS-CoV-2 infections and COVID-19-related deaths.

The analysis comprised 7,848 dialysis facilities that reported on a total of 518,798 patients, an estimated 90% of the total U.S. population on maintenance dialysis.

The study period captured the Delta wave (June 30 to Oct. 26, 2021), the first Omicron wave (Oct. 27, 2021 to March 22, 2022), and the second Omicron wave (March 23 to Sept. 27, 2022). Mean SARS-CoV-2 infection and death rates among dialysis patients were calculated as the sum of weekly cases divided by the weekly patient census during each wave.

As with the general population, the rates of infection and death fluctuated as the circulating variant changed. Both were highest during the first Omicron wave. During that wave, the overall infection rate among dialyzed patients was 46.25 per 10,000 patient-weeks and the death rate 2.66 per 10,000 patient-weeks. In the general U.S. population during that time, these rates were 43.62 and 0.26 per 10,000 population-weeks, respectively.

The findings pointed to the risks associated with travelling and gathering in healthcare facilities during times of high infection transmission, even for critical therapy, the authors noted.

“Most patients receiving dialysis must visit dialysis facilities to receive lifesaving treatment, which is performed in close proximity to other patients and facility staff members, three times each week. Many patients rely on shared transportation … and approximately 7% live in long-term care facilities, placing these persons at particularly high risk for infection and death related to COVID-19,” wrote Navarrete and colleagues.

But they also offered advice on precautions that can be taken during such times.

“The infection rate among persons receiving dialysis can be reduced by adherence to recommended infection prevention practices, including early detection of symptomatic illness, appropriate location of infected patients during in-facility dialysis treatments, correct use of personal protective equipment, and implementation of protocols to safely discontinue transmission-based precautions for affected patients,” they wrote.

Other limitations cited by the authors included that some deaths in the NHSN dataset may have been misclassified as COVID-related deaths. The researchers also were not able to assess patient covariates such as prior infection history or time since vaccination.

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