VAX-31 beat Pfizer and Merck’s established pneumococcal conjugate vaccines in a Phase 3 trial, exceeding investors’ most ambitious scenario and setting Vaxcyte up to challenge the Big Pharmas in a market worth $8 billion.
Vaxcyte’s investigational pneumococcal conjugate vaccine has achieved “near best-case scenario” data in a late-stage trial, matching existing shots on certain vaccine strains and beating them on others. The results sent the biotech’s shares up by more than 50% as investors welcomed a readout that could inject Vaxcyte into an $8 billion market.
VAX-31 met Pfizer’s existing pneumococcal conjugate vaccine (PCV) Prevar 20 and Merck’s Capvaxive on all 28 serotypes that one or both vaccines address, according to a Monday release. Vaxcyte’s option was superior to both vaccines on three unique serotypes. The Phase 3 trial met the co-primary endpoints that assessed non-inferiority of VAX-31 versus the marketed vaccines.
“[It] will be very difficult to refute that VAX-31 is showing best-in-class PCV potential here in this $8Bn+ (and growing) market,” Mizuho wrote in a Monday morning note.
Leerink Partners dubbed the readout “highly impressive.”
The firm predicted that Vaxcyte’s shares could climb to as high as $90–100—and indeed, the stock was sitting around $86 in pre-market trading, compared to $56 at close Friday.
VAX-31 is a next-generation 31-valent PCV candidate. The Phase 3 OPUS-1 trial was testing a high dose of the shot against Pfizer’s Prevnar 20 and Merck’s Capvaxive in 3,572 adults 50 years or older to determine safety, tolerability and immunogenicity. A smaller group of 475 adults ages 18–49 were also included.
Vaxcyte is positioning VAX-31 to address portions of the PCV market that are not served by the Big Pharma’s established brands. Investors had not been expecting such a clean win for the OPUS-1 trial, with forecasts that the shot would miss on a few serotypes.
Mizuho noted that while the shot met the broader criteria for non-inferiority, it did indeed narrowly fall to Capvaxive on two specific serotypes, but since investors’ best case was a miss on three or more, this shouldn’t be an issue.
Leerink Partners also brushed this off as a commercial concern, noting the beat of Pfizer’s option and that a miss here “is not an absence of protection.”
Vaxcyte also had a higher bar for assessing non-inferiority compared to the existing shots, which Leerink Partners said sets “a new competitive moat for future adult pneumococcal vaccine competitors.” With the lower bar, VAX-31 did beat Capvaxive.
With today’s results, the firm expects the shot could receive an FDA label as a 31-valent vaccine for 32 serotypes.
“We expect physicians and patients to prefer VAX-31 over Prevnar 20 and Capvaxive since it offers the broadest protection against disease,” Leerink Partners said.
The results bolster Vacyte’s overall platform, which also includes a Group A strep vaccine that entered Phase 1 testing this year, Leerink Partners said.
Vaxcyte will release further results from the late-stage OPUS-2 and OPUS-3 trials in the first half of 2027, which will support a regulatory filing in the first half of 2028. Leerink Partners expects a commercial launch that same year.
OPUS-2 is assessing the shot co-administered with a flu vaccine while OPUS-3 includes adults who have previously been vaccinated for pneumococcus. VAX-31 is also being tested for children in a Phase 2 trial, with a readout expected by the end of 2027.
Leerink is bullish that today’s results suggest success on the readouts to come.
