Two doses of recombinant zoster vaccine (RZV) are effective against herpes zoster (HZ), according to a study published in the Annals of Internal Medicine. Ousseny Zerbo, PhD, and colleagues conducted a prospective cohort study with adults aged 50 and older to evaluate the real-world effectiveness of RZV against HZ. The study included close to 2 million persons from four healthcare systems in the Vaccine Safety Datalink, with 7.6 million person-years of follow-up. After adjustment, vaccine efficacy (VE) was 64% for one dose and 76% for two doses. After one dose, VE was 70% in the first year, 45% in the second year, 48% in the third year, and 52% after the third year. With two doses, VE was 79% in the first year, 75% in the second year, and 73% in the third and fourth years. VE was 65% and 77% among those who did and did not receive corticosteroids before vaccination, respectively. “Our finding that the effectiveness of one dose decreased after a year further supports the current recommendation for a second dose,” Dr. Zerbo and colleagues wrote.