(Bloomberg) -- Merck & Co. won US approval for a pneumococcal vaccine that threatens to unseat one of Pfizer Inc.’s biggest franchises.

Called Capvaxive, Merck’s vaccine is approved to prevent the bacterial infections behind pneumonia and meningitis for adults over 18, Merck said Monday. 

Capvaxive has the potential to become the preferred vaccine given studies have shown it protects against bacterial strains that cause around 80% of pneumococcal diseases. Pfizer’s Prevnar works against 50%, to compare. Both products are indicated for people who have not previously received a pneumococcal vaccine.

Capvaxive’s commercial future rests with the Centers for Disease Control and Prevention, which will decide later this month whether to recommend Merck’s vaccine for adults over the age 50. Prevnar, which has nearly 95% market share, is recommended for those over 65. If the CDC gives preferential treatment to Capvaxive, Merck could gain substantial ground on Prevnar, a vaccine that brings in more than $6 billion in annual revenue for Pfizer, said Louise Chen, an analyst at Cantor Fitzgerald. People normally take this vaccine once in their lives.

Merck’s working to add new products as cancer blockbuster Keytruda, which accounts for nearly half of its revenue, faces price pressure later this decade. Capvaxive adds to Merck’s historically strong vaccines business, led by Gardasil, which protects against the cancer-linked virus HPV and brought in nearly $9 billion in revenue last year. Vaxneuvance, a pediatric pneumococcal vaccine approved in 2022, added $665 million in revenue last year and is expected to become a multibillion-dollar product. 

Merck’s case for Capvaxive is based in part on a clinical trial in which the vaccine outperformed Prevnar 20, Pfizer’s latest pneumococcal vaccine. For adults over 50, Merck’s shot generated immune responses comparable to Prevnar for the 10 bacterial strains common to both vaccines. In a test of Capvaxive on 11 more strains, Merck’s shot proved superior to Prevnar in 10 of them.

“That will really drop the overall load of pneumococcal disease not only in the older folks, who of course need it, but also in working adults,” said Eliav Barr, Merck’s chief medical officer. “That’s going to be important in reducing the overall burden of the disease.”

To health-care providers, the prospect of a more effective pneumococcal vaccine is “really exciting,” said Ann Philbrick, an associate professor at the family medicine department of the University of Minnesota. “Pneumonia is something that causes a lot of morbidity and mortality in the older population, and anything we can do to prevent that is needed,” she said.

Pneumococcal pneumonia hospitalizes about 150,000 adults in the US each year, according to Merck.

©2024 Bloomberg L.P.