Vaxcyte shares jumped more than 25% Monday after the company said its experimental pneumonia vaccine held up against the two shots now on the market in a large final-stage trial. The vaccine, called VAX-31, targets 31 strains of the bacteria that cause pneumonia, meningitis and bloodstream infections. It is set to compete with Pfizer's Prevnar 20, which covers 20 strains, and Merck's Capvaxive, which covers 21.

Vaxcyte said VAX-31 showed immune responses comparable to the rival shots on all 28 strains it shares with them. The company also said VAX-31 produced stronger immune responses than the existing shots on three strains only it covers. It fell short of the study's main target on two strains against Merck's shot. The company expects to report data from two more trials in the first half of 2027, and said it plans to seek FDA approval of the shot in the first half of 2028.