GlaxoSmithKline has beaten second-quarter profit expectations with the help of strong demand for its shingles vaccine, prompting the drugmaker to forecast a smaller fall in profit this year than originally anticipated.

GlaxoSmithKline (GSK) forecast that 2019 sales of its shingles vaccine would be more than £1bn (€1.1bn) but the drugmaker’s shares slipped on concerns about its pharmaceutical business and free cash flow.

The threat of slowing demand and new competition in GlaxoSmithKline’s flagship HIV drug business has unnerved investors in the UK’s biggest drugmaker, sending its shares down 1.8%.

GlaxoSmithKline (GSK) has filed its shingles vaccine Shingrix for US regulatory approval, the drugmaker said yesterday, bringing the potential $1bn (€918m)-a-year seller a step closer to market.