Among patients on hemodialysis (HD), a robust response to the Moderna mRNA COVID-19 vaccine occurs late in those without a prior COVID-19 infection, a new study finds.

A total of 61 patients (mean age 70 years; 95% male; 85% Black) on HD received the 2-dose Moderna vaccine at the dialysis unit of James J. Peters VA Medical Center in The Bronx, New York. Of these, 20 patients had been previously infected with COVID-19, 2 were diagnosed with COVID-19 within a week of the first vaccine dose, and 39 were uninfected. Prior to vaccination, SARS-CoV-2 immunoglobulin G (IgG) antibody titers measured by the Beckman Coulter IgG receptor binding domain (anti-RBD) assay were higher in patients with than without previous COVID-infection: 8.35 vs 0.03.

At 1 week after the first dose, median IgG antibody response was “robust” in the infected group and significantly higher than baseline: 33.33 vs 8.35, Aisha Shaikh, MD, and colleagues from the James J. Peters VA Medical Center, reported in the Clinical Journal of the American Society of Nephrology. There was no correlation between the number of days since COVID-19 infection and IgG antibodies. In the previously infected group, IgG titers were 33.33, 52.65, 51.85, and 56.40 at weeks 1, 2, 4, and 5, respectively. At week 4, patients received the second vaccine dose. At week 5, IgG titers were significantly higher compared with week 1 (56.4 vs 33.33), the investigators reported.

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In patients without prior COVID-19 infection, median IgG titers were 0.03, 0.4, 2.18, and 29.91 at weeks 1, 2, 4, and 5, respectively. IgG did not increase significantly until after week 4 when the second vaccine dose was administered, Dr Shaikh’s team reported. At week 5, IgG antibodies were significantly higher compared with week 1 (29.91 vs 0.03).

The investigators noted that 3 (uninfected) patients failed to mount an IgG antibody response after the second dose, including 1 patient receiving rituximab and prednisone.

None of the patients contracted COVID-19 in the 34 days after the second vaccine dose.

“In this report, 95% [of] HD patients mounted an anti-RBD IgG [antibody] response to the Moderna vaccine,” Dr Shaikh’s team wrote. “The timing of the [antibody] response was different in HD patients depending on prior COVID-19 history.”

The anti-RBD IgG antibody response in HD patients with prior COVID-19 was robust at 1 week after the first vaccine dose.  The robust anti-RBD antibody response in HD patients without prior COVID-19, however, did not occur until 5 weeks after the first vaccine dose (1 week after the second dose), “highlighting the importance of following the clinical trial vaccine administration protocol in HD patients. Whether a single Moderna vaccine dose provides effective protection in HD patients with prior COVID-19 requires further investigation.”

Results from this small study may not pertain to women, patients not receiving HD, or individuals receiving a COVID-19 vaccine other than Moderna, the investigators acknowledged.

Dr Shaikh and colleagues cautioned that seroconversion following vaccination in HD patients, while reassuring, still may not confer complete immunity against SARS-CoV-2.

Disclosure: Some [or one] study author(s) declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 


Chan L, Fuca N, Zeldis E, Campbell K, Shaikh A. Antibody response to mRNA-1273 SARS-CoV-2 vaccine in hemodialysis patients with and without prior COVID-19. Published May 24, 2021. Clin J Am Soc Nephrol. doi:10.2215/CJN.04080321