Pfizer is expanding its vaccine portfolio, developing other shots to cover entire lifespan

Pfizer is expanding its research on vaccines to eventually cover the entire lifespan, from shots for pregnant women to protect babies from the moment of birth to vaccines for senior citizens with waning immune systems.

The biggest U.S. drugmaker sells the world's top-selling vaccine, Prevnar 13 against ear, bloodstream and other infections, but until last year had no other vaccines.

It has since bought two others from Baxter, will soon acquire GlaxoSmithKline's vaccine against some strains of meningitis and is testing others against multiple deadly bacteria, a virus common in young adults, and against cancer and severe high cholesterol in older patients.

During a briefing with reporters, company officials said they're also developing a version of Prevnar for poor countries that doesn't need refrigeration.