The HZ/su vaccine has several advantages over the live attenuated HZ vaccine:3
- its adjuvant system stimulates strong cellular and humoral responses
- it achieves higher levels of effectiveness against acute HZ and PHN (about 90%)
- it can be used in patients who are immunocompromised
- no significant decline in efficacy has been observed between years one and four postimmunisation, and immune responses plateau for up to nine years. Duration of efficacy beyond four years is currently being studied.3,62,63
Furthermore, in a recent systematic review of the two zoster vaccines, the HZ/su vaccine, was statistically superior to both the live attenuated vaccine (vaccine efficacy, 85%; 95% credible interval, 31 to 98%) and placebo (vaccine efficacy, 94%; 95% credible interval, 79 to 98%).64
Nevertheless, the HZ/su vaccine had a much higher incidence of both local and systemic adverse reactions. It was associated with statistically more adverse events at injection sites than the live attenuated vaccine (relative risk, 1.79; 95% credible interval, 1.05 to 2.34; risk difference, 30%; 95% credible interval, 2 to 51%) and placebo (relative risk, 5.63; 95% credible interval, 3.57 to 7.29; risk difference, 53%; 95% credible interval, 30 to 73%). There were also statistically more systemic adverse events in subjects receiving HZ/su than in the placebo and the live attenuated HZ vaccine groups (relative risk, 2.28; 95% credible interval, 1.45 to 3.65; risk difference, 20%; 95% credible interval, 6 to 40%).64
The immunogenicity and efficacy of HZ/su vaccine depends on a two-dose regimen. In the phase III trials, 96% of subjects returned for a second dose.62,63 The compliance with a second dose in field conditions will become apparent soon from the US experience.
HZ is a common and often disabling condition in the older population. Although antivirals help to reduce the severity and duration of the acute phase, the main intervention available to reduce the incidence of PHN is vaccination with the live attenuated HZ vaccine.
A newer and more effective subunit recombinant HZ/su vaccine will become available to prevent HZ and will help to extend this protection to immunocompromised subjects.
GPs are key in achieving higher levels of vaccine coverage, as a recommendation to the patient to receive the HZ vaccine significantly increases the likelihood of the patient being vaccinated. MT