Was prior live-attenuated shingles vaccination associated with a lower likelihood of testing positive for COVID-19?

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The abstract describes the Bacillus Calmette–Guérin (BCG) vaccine as providing indirect protection against COVID-19, presumably through priming of the innate immune system. The researchers hypothesized that the live attenuated varicella zoster (LAVZ) vaccine, recommended for older adults, would also protect against COVID-19 infection.

They conducted a retrospective population-based cross-sectional study using the Leumit Health Services (LHS) database. LAVZ-vaccinated patients were matched with controls using a propensity score model with 1:9 nearest-neighbor matching. Matching was based on age, gender, and the presence of selected chronic disorders chosen for their association with COVID-19 infection.

Multivariate logistic regression analyses estimated the association between LAVZ vaccination and COVID-19 RT-PCR results, adjusting for sex, age, smoking status, comorbidities, and chronic medications associated with COVID-19 risk. The researchers identified 625 people who had received LAVZ vaccination and undergone COVID-19 RT-PCR testing. After 1:9 matching, the study included 6,250 people.

The multivariate logistic regression analysis found a statistically significant, independent negative association between prior LAVZ vaccination and the likelihood of COVID-19 infection: adjusted OR = 0.47 (95% CI 0.33–0.69, p < 0.001). The association strengthened further in a separate analysis based on the timing of LAVZ vaccination before COVID-19 RT-PCR testing. The researchers concluded that people aged ≥50 years who had received LAVZ vaccination had a lower likelihood of testing positive for COVID-19.