Analysts: GSK shingles vaccine could steal market share from Merck's Zostavax

While GlaxoSmithKline ($GSK) is still awaiting late-stage results for its shingles vaccine, HZ/su, Cowen & Co. analysts believe the vaccine may just be better than Merck's Zostavax.

The deciding factor? An advantage for HZ/su in older people.

The incidence of shingles increases with age, but Zostavax's ability to decrease risk of shingles declines in older people, the analysts wrote in a note. If Glaxo's double-blind trial--involving 16,000 people in 18 countries--shows a more "robust" response in the elderly, it would be a key differentiator to Zostavax.

Zostavax is the only shingles vaccine approved in the U.S. and the EU. Merck ($MRK) sold $765 million worth of Zostavax in 2014, but Glaxo's candidate has a chance to undermine its market position.

After approval, the analysts wrote, HZ/su "should be well positioned to capture market share from Zostavax." The analysts' sales forecast for HZ/su in 2017 is £10 million ($14.8 million) and £75 million ($111 million) in 2020.

The revenues would solidify GSK's No. 1 position in the worldwide vaccines market, a position it nabbed after it acquired the bulk of Novartis' ($NVS) vaccines unit. The British drugmaker leapfrogged Merck, which ranked No. 1 in 2013 sales.

Special Reports: The top 5 vaccine makers by 2013 revenue - GlaxoSmithKline - Merck | Top 10 best-selling vaccines of 2013

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