Drugmaker Pfizer says it's reducing what it charges humanitarian groups for its blockbuster vaccine against pneumonia, ear and blood infections.

Pfizer Inc.'s move to reduce Prevnar 13's price to $3.10 per dose—but only for the groups' use with refugees and in other emergency settings—follows pressure since 2009 by groups such as Doctors Without Borders.

"This is definitely a step in the right direction and will help to protect millions of ," the charity said.

The biggest U.S. drugmaker previously preferred tax-deductible donations, which don't impact Prevnar's much-higher price. Pfizer's top-selling product, which requires three doses, brings it some $5 billion a year.

Britain's GlaxoSmithKline Plc in September reduced the price of its rival Synflorix pneumococcal vaccine to $3.05 per dose for use in humanitarian emergencies.