induced protection cannot yet be determined. The vaccine appears to be about 90 percent effective against varicella in high-risk individuals and to be about 50 percent effective against herpes zoster in this group (Gershon et al., 1984).

Adverse reactions to the vaccines (detected in short-term follow-up) in field trials have been minor, mostly limited to a mild vesicular transient rash in a small percentage of vaccine recipients (Weibel et al., 1984).

Clinical trials have not posed any unusual logistic, ethical, or legal issues, and none are expected. Comprehensive analysis requires, however, that there be sufficient natural varicella occurring in the control group, against which to measure the protective efficacy in the vaccinated group. Maintenance of long-term surveillance of recipients to assess the frequency and severity of herpes-zoster, if it occurs, may be a problem in the future (McIntosh, 1984).

The health belief model parameters (perceptions of risk of illness, severity, vaccination benefits, and barriers) used to predict vaccine utilization are described in Chapter 6, where scores assigned to vaccines are displayed together for comparison.

Lay Acceptance Potential recipients in this target population probably have only a moderate perception of the likelihood of exposure and susceptibility to varicella, but they may be highly apprehensive about the severe consequences of the disease. High-risk recipients are likely to perceive the benefits of the vaccine to be high and the barriers low since it may prevent fatal disease.

Provider Acceptance Providers generally are aware of the risk and of the severity of the disease in this population. They may be somewhat skeptical, however, about the efficacy of the vaccine in this target population; hence, the vaccine received a moderate score for provider perception of vaccination benefits in this group. Perceived barriers to vaccination were judged to be very low, however, since the vaccine may prevent fatal disease in these patients. Overall, scores reflect the committee’s belief that the vaccine will be used extensively in high-risk individuals.

Lay Acceptance It is expected that the vaccine will be used much less frequently in this target population. Although most individuals accept the inevitability of exposure to varicella and the high proba-