Low humoral immune response to the BNT162b2 vaccine against COVID-19 in nursing home residents undergoing hemodialysis: a case-control observational study

Background Patients on hemodialysis (HD) face a high mortality risk from coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and they are therefore prioritized for vaccination. However, the efficacy of vaccination in this vulnerable population has not been confirmed. Although age is negatively correlated with serum immunoglobulin (Ig) levels, humoral responses to vaccination in elderly patients undergoing HD have not been investigated. To address this issue, we evaluated the anti-SARS-CoV-2 spike protein antibodies in nursing home residents on HD after BNT162b2 vaccine administration. Methods Patients on HD from a nursing home and care workers (controls) receiving two doses of the BNT162b2 vaccine between April and May 2021 were enrolled in this study. Those with a prior history of COVID-19 were excluded. Anti-spike protein antibodies were measured with the Elecsys (Roche) immunoassay system. Results The study included 26 nursing home residents (41% male; median age, 86 years) and 184 care workers (28% male; median age, 45 years). The median HD vintage was 51 months. After two doses of BNT162b2, 73% of the nursing home residents and 99.5% of the control group developed sufficient anti-spike protein antibodies (> 29 U/mL) to neutralize SARS-CoV-2. Three weeks after the second dose, median IgG titers of the residents and care workers were 83 [interquartile range (IQR) 17-511] and 1365 (IQR 847-2245) U/mL, respectively (p < 0.001). Conclusions The humoral response to BNT162b2 among elderly HD patients was relatively low; therefore, the optimal vaccination strategy for this population should be studied further to avoid COVID-19 outbreaks in healthcare facilities.