An investigational shingles vaccine, Zostavax, developed by Merck & Co, reduced the total burden of pain and discomfort caused by shingles by 61 percent in a study compared the investigational vaccine to placebo in more than 38,500 men and women age 60 and older.
Zostavax also reduced by 67 percent the incidence of persistent nerve pain - the most frequent complication of shingles known as postherpetic neuralgia ( PHN ) - and reduced the incidence of shingles by 51 percent.

The Phase III Shingles Prevention Study, published in The New England Journal of Medicine, was a Department of Veterans Affairs ( VA ) study conducted in collaboration with the National Institute of Allergy and Infectious Diseases ( NIAID ) at the National Institutes of Health ( NIH ) and Merck at 22 research sites across the United States over a period of more than five years.

The randomized, double-blind, placebo-controlled study was conducted to determine whether vaccination with a single dose of a live attenuated investigational vaccine, Zostavax, would decrease the incidence and/or severity of shingles and persistent nerve pain in men and women age 60 and older who had no previous history of shingles.

In the study, participants were randomized to groups given either Zostavax ( n=19,270 ) or a placebo ( n=19,276 ) and followed for the development of shingles for a median duration of 3.1 years.

Suspected cases of shingles were assessed by polymerase-chain-reaction ( PCR ) assay, virus culture and clinically by an evaluation committee consisting of five physicians with expertise in shingles.

All subjects with clinically diagnosed shingles were offered antiviral treatment ( Famciclovir ) when indicated or as appropriate and were offered standard-of-care treatment for pain.

The primary endpoint of the study was the burden of illness ( BOI ) caused by shingles over the first six months after shingles rash onset, a measure affected by the incidence, severity and duration of shingles-associated pain and discomfort.
Severity of pain was evaluated according to a "worst pain" score on a 0-to-10 scale using a validated questionnaire ( Zoster Brief Pain Inventory ) with a zero being no pain and a 10 being worst pain imaginable. Those in the study who did not develop shingles were assigned a score of zero. The BOI score represented the average severity of illness among all subjects in the vaccine or placebo group.

The study also evaluated the incidence of persistent long-term nerve pain after shingles in the group that received Zostavax compared to placebo.
PHN was defined as shingles-associated pain ( rated as greater than or equal to 3 on a 0-to-10 scale, using the Zoster Brief Pain Inventory ) that persisted or appeared more than 90 days after the onset of the shingles rash. The incidence of shingles in the group vaccinated with Zostavax compared to placebo recipients was also evaluated in the study.

The study showed efficacy with Zostavax on all measured endpoints compared to placebo: Zostavax significantly reduced the incidence, severity and duration ( burden of illness ) of pain and discomfort associated with shingles - by 61.1 percent ( p < 0.001 ); the overall BOI score was 2.21 for the vaccine group ( N=19,254 ) compared to a score of 5.68 in the placebo group ( N=19,247 ); Zostavax significantly reduced the incidence of persistent nerve pain after shingles - by two-thirds ( 66.5 percent ) ( p < 0.001 ); 27 cases of PHN occurred in the vaccine group ( N=19,254 ) compared to 80 cases in the placebo group ( N=19,247 ); Zostavax significantly reduced the overall incidence of shingles by 51.3 percent ( p < 0.001 ); 315 cases of shingles occurred in the vaccine group ( N=19,254 ) compared to 642 cases in the placebo group ( N=19,247 ).

In the study, the rates of serious adverse events, systemic adverse events and hospitalization were low.
During safety evaluations conducted during the first 42 days following vaccination, the number and types of serious adverse events were similar in the vaccine ( N=255/19,270 ) and the placebo groups ( N=254/19,276 ) and the distribution of serious adverse events by organ system were also similar between the groups.
Only five subjects had serious adverse events that were assessed by site investigators as possibly vaccine related, two in the vaccine group ( exacerbation of asthma and polymyalgia rheumatica ) and three in the placebo group ( anaphalactoid reaction, polymyalgia rheumatica and Good Pasture's syndrome ).
During this period, varicella-like ( chickenpox ) rashes at the injection site appeared more frequently in the vaccine group ( N=20/19,270 ) compared to the placebo group ( N=7/19,276 ). However, these rashes occurred at other sites at similar rates in the vaccine ( N=18/19,270 ) and placebo groups ( N=14/19,276 ).

In an adverse events sub-study that included more than 6,600 subjects from all 22 research sites, significantly more people in the vaccine group ( N=1,929/3,345 ) had one or more adverse events compared to the placebo group ( N=1,117/3,271 ) reflecting a greater frequency of injection-site adverse events in vaccine recipients.
The most frequently observed injection-site adverse events among those in the vaccine group were erythema ( redness ) ( 35.8 percent, compared to 7.0 percent with placebo ); pain or tenderness ( 34.5 percent, compared to 8.5 percent, with placebo ); swelling ( 26.2 percent, compared to 4.5 percent with placebo ); and pruritus ( itching ) ( 7.1 percent, compared to 1.0 percent with placebo ).
Reactions at the injection site were generally mild. No other adverse event at the injection site was observed in more than 2 percent of those in the vaccine group.

In the sub-study, significantly more people in the vaccine group experienced serious adverse events ( 1.9 percent ) than in the placebo group ( 1.3 percent; p=0.03 ); there were no significant differences in the distribution of serious adverse events by body system or event.
A subject-by-subject chart review of these serious adverse events revealed no clinically meaningful differences between the vaccine and placebo groups in the pathophysiology, nature, timing, intensity or outcome of these events.

Participants in the Shingles Prevention Study were enrolled between November 1998 and September 2001. Follow-up was completed in April 2004.
Participants had a history of varicella or had resided in the continental United States for at least 30 years.
Immunocompromised persons and those unable to adhere to assessments specified in the protocol were excluded from the study.
More than 95 percent of the subjects were actively followed to the end of the study.

Shingles is caused by the reactivation of latent varicella zoster virus - the same virus that causes chickenpox. Shingles may first appear as tingling, itching or pain on one side of the body or face. It then progresses to a blistering rash accompanied by pain in almost every case that varies in intensity and duration.
Shingles also can lead to complications, including persistent nerve pain ( PHN ) that can follow an episode of shingles. PHN can last for months or even years and can range from a tender, burning pain to a throbbing, stabbing pain.

Shingles can affect anyone who has had chickenpox - more than 90 percent of adults in the United States - and occurs most frequently in older adults. In fact, it is estimated that up to half of all people who reach age 85 will have developed shingles during their lifetime. Approximately 25 to 50 percent of shingles patients older than 50 years of age develop persistent long-lasting pain after shingles.
Estimates of the number of cases of shingles occurring each year vary from up to 800,000 to 1 million cases in the United States. The incidence of shingles is expected to increase as the population ages.

Source: The New England Journal of Medicine, 2005


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