Pfizer  (PFE - Get Report) posted slightly better-than-expected first-quarter earnings but missed analysts' forecasts for revenue amid a slowdown for sales of its key Prevnar 13 vaccine.

Pfizer reported adjusted first-quarter earnings per share of 69 cents, modestly ahead of the FactSet consensus of 67 cents and up 3% from the same period last year. Revenue, however, was $12.78 billion, down 2% from the first quarter in 2016 and missing the FactSet consensus of $13.09 billion.

"I was pleased with our first-quarter 2017 financial performance, which was in line with our expectations, and it reinforces our confidence in the business going forward," said CEO Ian Read. "I believe each of our businesses is well positioned within their individual markets with strong portfolios, highly skilled and accomplished leadership and focused strategies."

Sales of Prevnar 13, Pfizer's top-selling vaccine, saw sales of $1.392 billion, down from $1.5 billion over the same period last year. Lyrica IH sales, however, grew 12% to $1.13 billion, the company said. Pfizer's newest drug, Eucrisa, notched sales of $9 million, the company said, while another product addition, Xtandi, generated alliance revenue of $131 million.

Pfizer shares closed at $33.78 in New York Monday after falling around 0.35% on the session. So far this year, the stock has gained around 4% but has lagged both the 6.3% gain for the Dow Jones Industrial Average and the 10.3% advance for the benchmark S&P Pharmaceuticals Select Industry Index.