Herpes Zoster Vaccine Reduces Zoster Risk by Half

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Herpes Zoster Vaccine Reduces Zoster Risk by Half

January 11, 2011 — A new community-based study confirms that vaccination of adults older than 60 years with the herpes zoster vaccine (Zostavax, Merck & Co Inc) reduced subsequent herpes zoster cases by about 50% compared with those not vaccinated.

The study, using real-world data on people enrolled in the Kaiser Permanente Southern California health plan, is published in the January 12 issue of the Journal of the American Medical Association.

Dr. Hung Fu Tseng

The vaccine was approved by the US Food and Drug Administration (FDA) in 2006 and recommended for use in adults 60 years and older without contraindications by the Advisory Committee on Immunization Practices, Centers for Disease Control and Prevention (CDC), in 2007 when the practice was taken up in the Kaiser system, said lead study author Hung Fu Tseng, PhD, MPH, research scientist and epidemiologist at Kaiser Permanente Department of Research and Evaluation in San Francisco, California.

"What we found was that the vaccine performed similar to what has been found in the clinical trial data, and in addition, we found that the vaccine also works among the oldest old...as well as among people with chronic conditions and those of various racial groups," he told Medscape Medical News.

In a separate publication, a new study from CDC shows that at least by 2008 less than 7% of US seniors had chosen to get the herpes zoster vaccine. Investigators, with lead study coauthor Euler, an epidemiologist with the CDC’s National Center for Immunization and Respiratory Diseases, found low overall rates of vaccination that were particularly low among minority groups.

These findings are published online and will appear in the February issue of the American Journal of Preventive Medicine.

Shingles Prevention Study

The pain of herpes zoster is often disabling and can last for months or years, a complication called postherpetic neuralgia, the study authors write. About 1 million cases occur each year in the United States. Except for age and immunosuppression, risk factors are not really known, they note.

Results of the Shingles Prevention Study (SPS) showed that a vaccine prepared from the Oka/Merck strain of varicella zoster virus reduced the incidence of herpes zoster by about 51% (P < .001) and of postherpetic neuralgia by 67% (P < .001) among some 38,546 participants older than 60 years but without a history of herpes zoster, immunosuppression, or other conditions that would prevent participation (N Engl J Med. 2005;352:2271-2284).

In this study, Dr. Tseng and colleagues aimed to see whether these benefits in the "idealized" clinical trial setting would translate to the community when the vaccine was used in clinical practice. "This is particularly important for herpes zoster vaccine, given the medical and physiological diversity in the elderly population for whom the vaccine is indicated and since there are stringent storage and handling requirements for this live-attenuated vaccine," they write.

The researchers conducted a retrospective cohort study comparing the risk for herpes zoster among 75,761 plan members 60 years and older who were immunocompetent and received the vaccine with that of 227,283 unvaccinated age-matched members who did not receive the vaccine (matching of 3 unvaccinated members for each 1 vaccinated).

Compared with the unvaccinated cohort, vaccine recipients were more likely to be white, to be women, and to have had more outpatient visits and a lower prevalence of chronic diseases.

There were 5434 herpes zoster cases identified in the study, 6.4 cases per 1000 person-years among those vaccinated vs 13.0 cases per 1000 person-years among unvaccinated individuals. In the fully adjusted analysis, vaccination was associated with a 55% reduced risk for herpes zoster.

Table 1. Herpes Zoster Cases With Vaccine vs No Vaccine

Endpoint

Vaccinated (95% CI)

Unvaccinated (95% CI)

Hazard Ratio (95% CI)

Herpes zoster cases (per 1000 person-years)

6.4 (5.9 – 6.8)

13.0 (12.6 – 13.3)

0.45 (0.42 – 0.48)

CI = confidence interval

The reduction in risk did not vary by age at vaccination, sex, race, or presence of chronic diseases, the study authors write. Of note was the effect in those older than 80 years where there was still significant benefit from the vaccine, a finding that was divergent from findings of the SPS, Dr. Tseng said.

Vaccine recipients also had reduced risks for ophthalmic herpes zoster and hospitalizations coded as herpes zoster.

Table 2. Risk for Ophthalmic Herpes Zoster and Herpes Zoster Hospitalizations With Vaccine vs No Vaccine

Outcome

Hazard Ratio (95% CI)

Ophthalmic herpes zoster

0.37 (0.23 – 0.61)

Hospitalizations coded herpes zoster

0.35 (0.24 – 0.51)

CI = confidence interval

Because the vaccine was only licensed 4 years ago, the durability of its protection needs to be assessed in future studies, the study authors write. "Meanwhile, however, this vaccine has the potential to annually prevent tens of thousands of cases of herpes zoster and postherpetic neuralgia nationally."

To date, uptake of the vaccine "has been poor due to weaknesses in the adult vaccine infrastructure and also due to serious barriers to the vaccine among clinicians and patients," they conclude. "Solutions to these challenges need to be found so that individuals seeking to receive herpes zoster vaccine will be able to reduce their risk of experiencing this serious condition.

"I think the implication is because the lifetime risk is about 30% and the risk of shingles increases with age, persons over the age of 60 should probably consider talking with their physician about the possibility of receiving the vaccine to reduce the risk, and the physician can evaluate if the person is eligible or in healthy condition to receive the vaccine," Dr. Tseng concluded.

People ineligible for vaccination include those taking immunosuppressant agents, those who have leukemia or lymphoma, those who are HIV positive, or those who have had allergic reactions to components of the vaccine, he added.

Merck & Co Inc has applied to the FDA for use of the vaccine in those aged 50 to 59 years on the strength of a study showing a 70% reduction in zoster cases among vaccinated subjects over placebo. That study was presented at the 48th Infectious Diseases Society of America meeting in Vancouver, British Columbia, Canada.

Results Mirror Trials

Asked for comment on the study, Roos, MD, and Professor of Neurology and professor of neurological surgery at Indiana University School of Medicine, Indianapolis, and a member of the American Academy of Neurology, said that as the study authors note, these new results mirror those from the original clinical trials of the herpes zoster vaccine.

"The vaccine is associated with a 51% to 55% reduction in the incidence of herpes zoster," Dr. Roos told Medscape Medical News. "We do not know an individual's risk of zoster," she noted, "or what causes the virus to reactivate."

However, she pointed to some limitations of the study, including the retrospective design and relatively short period of follow-up, so that it's not clear at this time whether protective immunity declines over time. "Is the individual protected for 1 year, 2 years, 3 years?" she said.

Finally, Dr. Roos said, the study authors do not report adverse events related to the vaccine. "In the original Shingles Prevention Study, there were more cardiac events in the vaccine recipients than in the placebo recipients."

The study did not receive external funding. Dr. Tseng reports having received research funding from Merck for other vaccine studies. Disclosures for the coauthors appear in the original paper. Dr. Roos has disclosed no relevant financial relationships.

JAMA. 2011;305:160-166.

http://www.medscape.com/viewarticle/735609