* Vaccines unit sales surge 20 percent, led by Shingrix
* Advair sales drop 15 percent
* Shingrix sales to be "significantly" more than 1 bln stg (Adds details from media call, adds share movement)
By Ankur Banerjee and Pushkala Aripaka
May 1 (Reuters) - GlaxoSmithKline forecast 2019 sales of its fast-growing shingles vaccine Shingrix to be "significantly" more than 1 billion pounds ($1.31 billion) on Wednesday as the British drugmaker outpaced first quarter forecasts.
Shingrix, launched in 2017, is an important source of growth for Chief Executive Officer Emma Walmsley, as she strives to improve GSK's commercial performance after streamlining its operations and spinning off or selling units.
"Shingrix has delivered another fantastic performance in the quarter," Walmsley told journalists on a GSK results call.
Sales of the treatment for shingles, a viral infection of the skin that causes painful rashes, were 357 million pounds in the quarter to the end of March, up 61.5 percent from the fourth quarter.
Analysts expected quarterly sales of 249 million pounds and are forecasting 2019 sales of 1.17 billion pounds.
Shingrix sales were largely driven by the United States, which benefited from market growth in new patient populations covered by immunisation recommendations as well as growth in Canada and the drug's recent launch in Germany.
Sales of the company's asthma treatment Advair, however, fell 15 percent to 486 million pounds in the quarter, due to competition from a generic version.
Jefferies analyst Peter Welford said the Shingrix performance is positive as a key future growth driver, but GSK's pharma unit performance is likely to be perceived as broadly in-line given Advair now faces U.S. generic erosion.
GSK's turnover rose to 7.66 billion pounds ($10 billion) in the quarter, from 7.22 billion pounds a year earlier, and above a company-provided consensus here of analysts' forecasts of 7.56 billion pounds.
Adjusted operating profit was 30.1 pence per share in the quarter, versus expectations of 26.1 pence per share.
"We have made a strong start to 2019, which is an important year of execution for GSK, with growth in sales, operating margins and earnings per share in Q1," Walmsley said in a statement accompanying the results.
FTSE-100 member GSK, whose shares were up 0.3 percent to 1,580 pence at 1156 GMT, also said it had decided to stop the clinical development of its next generation strep pneumonia candidate vaccine and the candidate for a universal flu vaccine.
The company, which reiterated its 2019 forecast of a decline in adjusted earnings of 5 to 9 percent, said its quarterly earnings were hurt by continuing pricing pressure and investments in promotions, particularly for new launches. ($1 = 0.7653 pounds) (Reporting by Pushkala Aripaka, Noor Zainab Hussain and Ankur Banerjee in Bengaluru Editing by Saumyadeb Chakrabarty, Patrick Graham and Alexander Smith)