medwireNews: Two doses of the recombinant zoster vaccine (RZV) are 76% effective at protecting against incident herpes zoster (HZ), with the level of protection largely maintained over a 4-year period, indicate findings from a real-world study published in the Annals of Internal Medicine.
The study of nearly 2 million people, who contributed 7.6 million person–years of follow-up, shows that in fully vaccinated individuals, the vaccine was 79% effective (calculated as 1 minus the adjusted hazard ratio) during the first year, 75% during the second year, and 73% during the third and fourth years.
By contrast, in partially vaccinated people, who received only one dose of the RZV, the vaccine was 64% effective overall, but this effectiveness declined significantly from 70% in the first year to 45% in the second year, 48% in the third year, and 52% after the third year.
Notably, “[e]ffectiveness for fully vaccinated persons did not differ by whether the second dose was given after the recommended 6 months,” report Ousseny Zerbo (Kaiser Permanente Northern California, Vaccine Study Center, Oakland, USA) and team. It was 76% effective when the second dose was given within 6 months of the first, 78% when given between 6 months and 1 year, and 75% when given after a year.
“This finding provides reassurance about the effectiveness of the second dose even if receipt of it was delayed due to vaccine shortage or other factors,” they add.
The study was conducted from 2018 through 2022 and involved Vaccine Safety Datalink members aged at least 50 years who were eligible for HZ vaccination. Among 1,996,885 participants, 38% were aged 65 years or older, 53% were women, and 59% were White.
During the study period, 38% of participants received at least one dose of the RZV and 29% received two doses. During an average follow-up of 1.4–1.6 years after vaccination, there were 45,333 new cases of HZ, 94% of which occurred in unvaccinated people.
The researchers note that among fully vaccinated individuals, the RZV was slightly more effective in those who received it by the age of 65 years, at 81% compared with 74% among individuals vaccinated at 65 years of age or older.
The investigators also found that vaccine effectiveness was “lower but still substantial” among a subgroup of individuals who were possibly immunocompromised at the time of vaccination due to using corticosteroids in the 3 months leading up to vaccination, at 65% versus 77% among those who were not immunocompromised.
The researchers conclude that the use of “2 doses of RZV showed high effectiveness that waned very little over 4 years.” They also highlight that the “substantial [vaccine effectiveness] among corticosteroid recipients underscores the value of vaccination for these persons, who are at increased risk for HZ.”
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