Study: Herpes Zoster Vaccine Efficacy Decreased Steadily Over 8-Year Period
An investigational vaccine currently being developed doesn’t appear to have the same time-related loss of efficacy.
A review of more than 176,000 people who were vaccinated against herpes zoster showed that the vaccine's effectiveness declined rapidly and appeared to provide little or no protection after 8 years.
“Given the high incidence of HZ among seniors, the number needed to vaccinate to avert 1 episode occurring over these 8 years, was just 29, demonstrating that vaccination provides real initial benefit,” the researchers wrote in Journal of Infectious Diseases. “However, the vaccine appears to provide little protection against HZ beyond 8 years, in which case the number needed to vaccine would subsequently increase quickly with time.”
Researchers at Kaiser Permanente Southern California and the Centers for Disease Control and Prevention in Atlanta examined electronic health records collected on 176,078 Southern Californians aged 60 or older who received the vaccination from January 2007 to December 2014. Also included in the study were 528,234 unvaccinated, age-matched controls.
As expected, vaccination was associated with a reduced risk of herpes zoster in the adjusted analysis (HR=0.51; 95% CI, .49–.52). The protective effect extended to all age groups and to patients with chronic diseases. The adjusted HR increased from 0.44 (95% CI,.41–.47) for the group aged 60–64 years to 0.58 (95% CI, .53–.64) for the group aged ≥80 years.
Tseng et al noticed that the efficacy of the vaccine decreased over time, from of 68.7% (95% CI, 66.3% to 70.9%) at year 1 to 4.2% (95% CI, −24.0% to 25.9%) during year 8 (see graph). This pattern was consistent for the cohort aged 60–69 years and the cohort aged ≥70 years). The 8-year cumulative risk for herpes zoster was 7.07% in the vaccinated groups and 10.54% in the unvaccinated groups.
Myron J. Levin, MD, professor in the infectious disease division at the University of Colorado Anschutz Medical Campus said an investigational vaccine currently being developed doesn't appear to have the same time-related loss of efficacy. However, until that vaccine becomes available, the strategy for vaccinating aging patients against herpes zoster is unclear.
“Boosting an older person 8 or 10 years after the initial vaccination would be protective for some period of time. The problem is with the current vaccine, and almost every vaccine in aging people, the older you are, the less of an advantage you get from the vaccine. I think that would be true even if you boosted the vaccine,” he said. “It would be nice if we had a better vaccine. Meanwhile, the original vaccine, which was a good thing, stops being a good thing after six or seven years. What we need is a strategy and the truth is, we don't know what the strategy is yet. We know it's possible to give more of the live vaccine. We know that we have a better vaccine and maybe that's what we should be boosting with. We're in a waiting period to find out what's the right way to go.”
Disclosures: Dr. Levin is an advisory board member for GlaxoSmithKline and Merck, and holds a patent for Zostavax (zoster vaccine live) with Merck.