Vaxcyte Stock Jumps 56 Percent After Its 31-Strain Pneumonia Vaccine Meets Goals Against Pfizer and Merck

Vaxcyte shares jumped 56 percent on Monday after the company said its experimental pneumococcal vaccine met the main goals of a late-stage study in adults 50 and older, putting a 31-strain shot on a path to compete with Pfizer and Merck.

The stock traded at $88.04, up $31.56, or 55.87 percent, in early dealings. It had been up as much as 91 percent before the opening bell. Friday's close was about $56.48. The move took the shares to their highest level in nearly two years, above a prior 52-week high of $65.

Vaxcyte said VAX-31, its 31-valent pneumococcal conjugate vaccine, met all prespecified primary endpoints across the age groups studied, compared with Pfizer's Prevnar 20 and Merck's Capvaxive. The trial, OPUS-1, enrolled 4,047 people at about 30 U.S. sites. Adults 50 and older were randomized to a single dose of VAX-31, Prevnar 20 or Capvaxive. Adults 18 to 49 received VAX-31 or Prevnar 20.

Pneumococcal bacteria can cause pneumonia, meningitis and bloodstream infection. Older adults are the group most at risk, which is why the adult comparison is the one that moves the stock. Prevnar 20 covers 20 strains. Capvaxive covers 21. VAX-31 is designed to cover 31.

The company said immune responses were at least comparable to the rivals against the 28 strains shared with one or both marketed vaccines, and stronger against three strains unique to VAX-31 and against strain 20B. In separate comparisons, VAX-31 met the study's efficacy benchmark for all 20 strains shared with Prevnar 20 and for 17 of 19 shared with Capvaxive. On the other two strains shared with Capvaxive, it missed the study's stricter bar and met a less stringent threshold used in earlier vaccine studies. Safety was consistent across age groups, the company said, with no serious adverse events considered related to the vaccines.

The readout is immune response, not a count of prevented infections. Regulators have accepted that antibody standard for pneumococcal conjugates. It is still a proxy. A shot that matches Prevnar on shared strains and adds coverage is the commercial argument. A shot that missed a stricter bar on two strains is the caveat Merck's investors will use.

The calendar is long. Vaxcyte expects results from two other late-stage trials in the first half of 2027 and plans a U.S. marketing application in the first half of 2028. Approval, if it comes, is years from a Monday stock move. Manufacturing a 31-valent conjugate at commercial scale is the other unpriced risk. Pfizer and Merck already sell into this market and can answer with price, contracts and their own next-generation shots.

Guggenheim analyst Seamus Fernandez raised his price target to $125 from $116 and kept a buy rating, calling the shares a top pick. The average target before the move was about $109. At $88 the stock is still below the new Guggenheim figure and far above Friday's close. A 56 percent gain prices the chance that a small biotech can take share in a market owned by two of the largest drugmakers. It does not price an approved product. The company said the primary goals were met. The application is aimed at 2028.