Because efficacy of the shingles vaccine appears to wane over time, it should not routinely be given to people in their 50s, according to information presented at a meeting of the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices.
"At this time, there is insufficient evidence supporting long-term protection of the vaccine, so if people younger than 60 [years] are vaccinated, they might not be protected when chance of disease is highest," said Dr. Jeff Duchin, chair of the ACIP’s herpes zoster working group. "We will continue to monitor data as they becomes available, but at this point we are reaffirming that vaccination be done in those age 60 [years] and older."
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There is "insufficient evidence" regarding the efficacy of shingles vaccines for long-term protection, said Dr. Jeff Duchin.
The committee made its recommendation after reviewing newly released data from Merck’s Long-Term Persistence Study for shingles. It found that, 10 years after vaccination, the overall incidence rate of shingles had increased from about 4/1,000 person-years to 11/1,000 person-years. The observed incidence rate of shingles in historical controls is about 13 cases/1,000 person-years.
Dr. Janie Parrino, director of vaccine clinical research at Merck Research Laboratories, presented results of the company’s latest study of the vaccine’s extended efficacy. The shingles Long-Term Persistence Study is an 8-year follow-up of the Shingles Prevention Study, in which subjects were randomized to Merck’s Zostavax vaccine or placebo. It showed that the vaccine significantly reduced the incidence of herpes zoster and postherpetic neuralgia (PHN) as well as the shingles burden of illness, in adults older than 60 years.
A short-term follow-up study appeared last year; it added 4 more years of follow-up data on more than 14,000 of the original cohort.
It found a gradual decrease in vaccine efficacy by 6-7 years after vaccination. "Analysis of vaccine efficacy in each year after vaccination for all outcomes showed a decrease after year 1, with a further decline thereafter," the investigators said. "Vaccine efficacy was statistically significant for the incidence of herpes zoster and herpes zoster burden of illness through year 5 after vaccination, but vaccine efficacy is uncertain beyond that point."
The long-term study presented at the Atlanta meeting involved up to 12 years of data on almost 7,000 people in the original cohort. It demonstrated a continuous time-bound waning of efficacy.
In addition to the increasing annual incidence of shingles, the study found an increasing incidence of PHN, from less than 1/1,000 person-years during the year of vaccination to about 1/1,000 person years by year 10. However, the incidence among placebo subjects and historical controls was more than 2/1,000 person years by that time. The shingles burden of illness (a measure of acute pain) also increased as time passed, Dr. Parrino noted.
Taking into account both clinical efficacy and cost, Ismael Ortega-Sanchez, Ph.D., a health economist with the CDC, concluded that the shingles vaccine is most effective when given to people in their 60s and 70s.
Vaccinating from age 50-59 years would prevent about 20,000 shingles cases annually. But vaccinating in the 60s would prevent 26,000 and, in the 70s, 21,000. The trend was similar for cases of PHN: prevention of 1,000 cases for vaccinating in the 50s, 4,000 for vaccinating in the 60s, and 8,000 for vaccinating in the 70s.
Other outcomes – emergency visits, ambulatory visits, hospitalizations, length of hospital stay, and prescriptions – also increased significantly over the 3 decades.
Savings tracked clinical outcomes in a value assessment model of 6 million people: 1 million vaccinated and unvaccinated in each of the three age cohorts.
Compared with not vaccinating, vaccinating those in their 50s would save $16.8 million annually. Vaccinating during the 60s would save about $24.3 million, and during the 70s, $31.9 million.
And, because younger people are likely to have more systemic reactions, they cost more to vaccinate. A model that accounted for the cost of the vaccine, administration, and treating local and systemic reactions, put the total price tag at $193 million for those in their 50s, and $190 million for each of the two older groups.
Finally, the number needed to treat to prevent one case of shingles, PHN, or non-PHN complication case was higher in those in their 50s than in those in their 60s or 70s (one shingles case – 51, 38, and 47 respectively; one PHN case – 988, 247, and 124).
"This isn’t intended to tell people not to get the vaccine early, but to make them aware of the risks and benefits, given that the greatest risk of the disease is later in life," Dr. Duchin said. Since there are no data on booster shingles vaccines, he said "we only have one shot at this and we need to focus our efforts on those at the greatest risk."