In a 15,411-patient Phase III trial, GlaxoSmithKline's Shingrix vaccine provided 97% protection against herpes zoster in patients aged 50 years and older, with a stable effect across all age groups (New Engl. J. Med. 28 Apr 2015). This first of seven ongoing Phase III trials bodes well for the adjuvanted herpes zoster subunit vaccine. By contrast, Merck & Co.'s approved live attenuated herpes zoster vaccine Zostavax reduced the incidence of herpes zoster by 70% in 50–59-year-olds, by 64% in 60–69-year-olds and by 38% in people aged 70 and older in its pivotal trials.

“The results for this vaccine are promising and may provide an important addition to vaccinations for an aging population,” writes medical virologist Jeffrey Cohen, of the US National Institute of Allergy and Infectious Diseases, in an accompanying editorial (New Engl. J. Med. 28 Apr 2015). He adds that whereas Zostavax is contraindicated in people with impaired cellular immunity, who are at highest risk for herpes zoster, the subunit vaccine may provide a safe therapeutic option for these at-risk individuals. But, systemic adverse events were more than twofold more frequent in the Shingrix arm than in the placebo arm of the trial, providing some cause for pause. And Cohen noted that ongoing clinical trials still need to shed light on the duration of the effect of GSK's vaccine and on its ability to prevent post-herpetic neuralgia and other complications of herpes zoster in aged individuals.

Analysts expect GSK to file the vaccine for regulatory approval in the United States and in the European Union in 2016.

The vaccine uses the as-yet unapproved AS01B adjuvant, which is also a component of GSK's RTS,S malaria vaccine (also known as Mosquirix). RTS,S is currently under review with European regulators.