Background: Vaccination is the most effective strategy for preventing infectious diseases and related complications, and proving its efficacy is crucial for its success and adherence, especially for newly introduced vaccines, such as adjuvanted recombinant herpes zoster virus vaccination (RZV). In this observational real-life study, we recorded adverse effects following immunization (AEFIs) after RZV administration in frail populations. Methods: A total of 271 subjects underwent RZV at Vaccination Center, University Hospital “San Giovanni di Dio e Ruggi d’Aragona”, Salerno, Italy. Most subjects were solid organ transplant recipients (kidney, 77.1%; liver, 4.8%). Demographics, clinical data, and AEFIs (type, duration, and medications used) were recorded. Results: Overall, 37% of participants reported at least one AEFI following the first dose, predominantly pain at the injection site (60%), while 41% did so after the second dose (pain at the injection site in 62% of cases). Medications were more frequently used for AEFI treatment after the second dose (28%) rather than after the first dose (13%) (p = 0.01). After stratification by sex, females experienced AEFIs more frequently than males, particularly local skin reactions. Conclusions: Our study added evidence of safety and tolerability of the adjuvanted recombinant RZV in frail adults.
