Lower risk for COVID-19 hospitalization among patients in the United States with past vaccinations for herpes zoster and tetanus, diphtheria and pertussis.

Influenza, tetanus, diphtheria, and herpes zoster (HZ) vaccination received within 10 years of the COVID-19 pandemic have been associated with less severe COVID-19 infection. We expanded on this evidence to determine if a receiving two different vaccinations (i.e., HZ and tetanus, diphtheria, and pertussis (Tdap)) was associated with a lower risk for COVID-19 hospitalization. De-identified medical record data from a large mid-western health care system was used to determine if, compared to those with neither HZ or Tdap vaccination, patients with either HZ or Tdap and patients with both HZ and Tdap vaccination had lower risk for COVID-19 hospitalization between 4/1/2020 and 12/31/2020. Confounding was controlled using entropy balancing. Patients (n = 363,293) were 71.5 (±8.4) years of age, 57.8% female and 89.2% White race. Prior to controlling for confounding, as compared to patients without either vaccination, those that had either HZ or Tdap were significantly less likely to have a COVID-19 hospitalization (RR = 0.85; 95 %CI: 0.75-0.95). The risk for hospitalization decreased further among those with both HZ and Tdap vaccination (RR = 0.45; 95 %CI:0.28-0.71). After controlling for confounding, including healthy patient bias, receiving both vs. neither vaccinations remained significantly associated with a lower risk of COVID-19 hospitalization (RR = 0.48; 95 %CI: 0.26-0.90). Receiving both Tdap and HZ vaccination is associated with lower risk for COVID-19 hospitalization. Whether there is any benefit of past vaccination exposure in COVID-19 vaccinated patients should be investigated.