A Cochrane review [Abstract] 1 included 26 studies with a total of 90 259 subjects. Only three studies assessed the incidence of herpes zoster in groups that received vaccines versus placebo. Most studies were conducted in high-income countries in Europe and North America and included healthy Caucasians aged 60 years or over with no immunosuppressive comorbidities. 16 studies used live zoster vaccine (LZV). 10 studies tested a recombinant zoster vaccine (RZV).
The incidence of herpes zoster at up to 3 years follow-up was lower in participants who received the LZV (one dose subcutaneously) than in those who received placebo (RR) 0.49, 95% CI 0.43 to 0.56; risk difference (RD) 2%; number needed to treat for an additional beneficial outcome (NNTB) 50) in the largest study, which included 38 546 participants. There were no differences between the vaccinated and placebo groups for serious adverse events (RR 1.08, 95% CI 0.95 to 1.21) or deaths (RR 1.01, 95% CI 0.92 to 1.11). The vaccinated group had a higher incidence of one or more adverse events (RR 1.71, 95% CI 1.38 to 2.11; RD 23%; number needed to treat for an additional harmful outcome (NNTH) 4.3) and injection site adverse events (RR 3.73, 95% CI 1.93 to 7.21; RD 28%; NNTH 3.6) of mild to moderate intensity. These data came from four studies with 6980 participants aged 60 years or over.
Two studies (29 311 participants for safety evaluation and 22 022 participants for efficacy evaluation) compared RZV (two doses intramuscularly, two months apart) versus placebo. Participants who received the new vaccine had a lower incidence of herpes zoster at 3.2 years follow-up (RR 0.08, 95% CI 0.03 to 0.23; RD 3%; NNTB 33). There were no differences between the vaccinated and placebo groups in incidence of serious adverse events (RR 0.97, 95% CI 0.91 to 1.03) or deaths (RR 0.94, 95% CI 0.84 to 1.04). The vaccinated group had a higher incidence of adverse events, any systemic symptom (RR 2.23, 95% CI 2.12 to 2.34; RD 33%; NNTH 3.0), and any local symptom (RR 6.89, 95% CI 6.37 to 7.45; RD 67%; NNTH 1.5). Although most participants reported that there symptoms were of mild to moderate intensity, the risk of dropouts (participants not returning for the second dose, two months after the first dose) was higher in the vaccine group than in the placebo group (RR 1.25, 95% CI 1.13 to 1.39; RD 1%).
RZV was more effective than LZV but there are no head-to-head comparisons. The main studies did not follow participants for more than 3 years.
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