We analyzed this claim: is it true that
Vaxcyte's experimental VAX-31 vaccine met its main late-stage trial goals against approved shots from Pfizer and Merck?
Company data show VAX-31 triggered the required immune protection across all targeted bacterial strains, although it trailed Merck's shot on two individual strains and is not yet approved
Vaxcyte clears key adult vaccine hurdle
California biotech company Vaxcyte said its experimental 31-strain shot matched or beat current Pfizer and Merck vaccines in a late-stage immune-response trial.
In a nutshell
Vaxcyte's experimental 31-strain vaccine passed its first major late-stage trial, producing strong immune defenses against severe bacterial infections in adults without new safety alarms. The shot matched Pfizer's Prevnar 20 on all shared bacterial strains and met overall study goals against Merck's Capvaxive, despite trailing on two individual strains. Vaxcyte is now raising $1 billion to fund final clinical tests, factory preparation and an intended 2028 U.S. approval bid.
Highlights
- VAX-31 met all primary safety and immune-response goals in a trial of more than 4,000 adult volunteers
- The vaccine matched Pfizer's Prevnar 20 across all 20 shared bacterial strains and beat comparator shots on new strains
- The shot trailed Merck's Capvaxive under strict criteria on two of 19 shared strains
- Vaxcyte launched a $1 billion stock and debt offering to prepare for manufacturing and commercial rollout
- Vaxcyte expects two companion trial readouts in 2027 before seeking U.S. approval in 2028
Bacterial strain coverage across adult pneumococcal vaccines
| Vaccine | Bacterial strains covered |
|---|---|
| Pfizer Prevnar 20 | 20 |
| Merck Capvaxive | 21 |
| Vaxcyte VAX-31 | 31 |
- Bacterial strains included in approved adult pneumonia vaccines compared with Vaxcyte's experimental shot
- Broader strain coverage aims to protect adults against more bacterial types without weakening overall immune defense
From the Editor’s Diary
Broader vaccines can shield against more disease varieties, but drugmakers must convince regulators that adding extra targets never dilutes defense against the most common threats.
Who's involved
Vaxcyte
Clinical-stage vaccine developer based in San Carlos, California
goal → Win regulatory approval for a shot that covers 31 bacterial strains without losing potency
U.S. Food and Drug Administration
Federal agency that reviews and licenses medical treatments in the United States
goal → Decide whether VAX-31 meets safety, effectiveness and manufacturing rules for commercial sale
Pfizer
Global pharmaceutical company that makes the approved 20-strain shot Prevnar 20
goal → Protect its established pneumococcal vaccine franchise against broader new rivals
Merck & Co.
Global drugmaker that makes the approved 21-strain vaccine Capvaxive
goal → Maintain market share for its adult shot, especially against strains common in U.S. illness
In short
Vaxcyte's experimental vaccine could widen adult protection against Streptococcus pneumoniae, a common bacterium behind severe pneumonia, bloodstream infections and meningitis, beyond what existing shots cover.
The success makes a U.S. regulatory filing likely in the first half of 2028, once follow-up studies conclude.
That timeline is likely but not guaranteed, because the shot must still pass two more late-stage trials, a manufacturing review and full scrutiny by federal regulators.
How it unfolded
Early trial data advance VAX-31
Vaxcyte selected VAX-31 as its lead candidate after positive mid-stage testing, moving the 31-strain vaccine toward final clinical trials.
U.S. regulators map the testing path
U.S. officials granted VAX-31 expedited review status and helped set the patient numbers and benchmarks needed for eventual approval.
The pivotal trial starts and finishes sign-ups
Researchers opened the main trial comparing VAX-31 directly with Pfizer's and Merck's shots, completing patient sign-ups within months.
Vaxcyte readies data for public release
Company leaders met regulatory officials and narrowed the expected timeline for delivering the first trial results.
Trial results show broad protection
Vaxcyte disclosed that VAX-31 hit all primary goals, matching competitor shots on most shared strains while beating them on new ones.
New fundraising cools stock rally
Following the clinical win, Vaxcyte moved to raise $1 billion for commercial launch preparations, sending its shares lower.
Where things stand
VAX-31 has shown strong early Phase 3 immune and safety marks, but it does not yet have regulatory clearance. The trial measured antibody levels in blood rather than real-world disease rates, and the full results have not yet gone through academic peer review.
Federal approval remains several steps away. Vaxcyte plans to report results from two companion trials in early 2027 and complete factory-consistency checks before filing for U.S. licensure in the first half of 2028.