A transient reduction of the varicella-zoster virus-specific immunoglobulin G level after vaccination against severe acute respiratory syndrome coronavirus 2 with an mRNA vaccine in nursing home residents, but not staff.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccines are highly effective in protecting against severe disease and hospitalization. However, a potential risk of herpes zoster (HZ) has been identified after vaccination against SARS-CoV-2 mRNA vaccine. To evaluate the effect of the vaccination on immune response against varicella-zoster virus (VZV), the immunoglobulin G (IgG) titers against VZV and measles virus (MV) as a control, before and after the vaccination in residents and staff of two nursing homes. The geometric mean VZV IgG titer in 24 residents (range, 74-100 years) at two months after the second dose of vaccine decreased significantly from that before the vaccine; however, it recovered to the same level as before vaccination at five months after the second dose and decreased again at two months after the third dose. In contrast, the geometric mean VZV IgG and MV IgG titers in 22 staff (range, 20-69 years) were not significantly different than before vaccination, two, and five months after the second dose of vaccine, and two and five months after the third dose. This study has revealed that VZV IgG and MV IgG titers were temporarily reduced in nursing home residents, but not in staff, after immunization against SARS-CoV-2, suggesting an effect on antibody production.