The adult pneumococcal vaccine met every primary endpoint in its pivotal trial. The two comparisons it missed on a stricter bar are against Merck's Capvaxive, the matchup the company expects regulators to study most closely.
Equity Markets · FinancialMarkets.com · · Tickers: PCVX, MRK, PFE, XBI
Vaxcyte's market value swung by about $4.9 billion between Friday's close and Monday's first-half-hour peak. By early afternoon the company held on to about $2.5 billion of it.
The stock ended Friday at $56.48. It opened Monday at $87.21 and reached $90.75 in the first half hour, a gain of about 61%. By the 10:30 a.m. Eastern half hour it had dropped below $77, and it then settled into a band between roughly $72 and $77. Near 2 p.m. it traded around $74.10, up about 31%, having surrendered close to half of the peak gain.
The scorecard
The trigger was topline data from OPUS-1, the pivotal Phase 3 study of VAX-31 in adults. The vaccine targets 31 pneumococcal serotypes, more than either Pfizer's Prevnar 20 or Merck's Capvaxive, the two approved adult shots. Vaxcyte said VAX-31 met all of the trial's prespecified primary endpoints.
The detail sits in the individual comparisons. The trial used a stricter noninferiority margin than regulators have historically applied. Against Prevnar 20, VAX-31 cleared that tighter bar on all 20 shared serotypes. Against Capvaxive it cleared it on 17 of 19. Put together, that is 37 passes in 39 head-to-head tests, or about 95%. The two exceptions, serotypes 3 and 12F, fell below the stricter cutoff against Capvaxive while still meeting the older, looser one.
Elsewhere the results were clean. On the serotypes only VAX-31 covers, plus one cross-reactive type, it showed superior immune responses. Younger adults aged 18 to 49 responded in line with those aged 50 to 64 across all 32 comparisons, and the safety profile resembled the marketed shots. The trial dosed 4,047 people at about 30 U.S. sites. All of these measures are immune responses, not rates of disease prevented.
Where scrutiny falls
Vaxcyte pointed to the Capvaxive matchup itself. "Given current U.S. epidemiology, with the serotypes unique to PCV21 accounting for a larger share of adult disease, we expect the comparison of VAX-31 to PCV21 to be a particular focus of FDA review," said James Wassil, its chief scientific and operating officer. PCV21 is Capvaxive.
The road to a filing is long. Two further Phase 3 studies, OPUS-2 and OPUS-3, read out in the first half of 2027, a manufacturing consistency study follows, and Vaxcyte plans to submit for approval in the first half of 2028.
The incumbents
Merck shares fell about 2.9% and Pfizer about 1.6%, while the health-care sector as a whole gained about 0.5%. Size argues against reading too much into Merck's move. A 2.9% drop on Merck's market value of roughly $346 billion is about $10 billion, around four times the value Vaxcyte added by early afternoon. The two moves fell on the same day; the arithmetic does not show one driving the other.
What analysts said
Guggenheim lifted its price target to $125 from $116 and reiterated Buy. Mizuho analysts said investors' best case going in had been a miss on three or more serotypes against Capvaxive. Leerink Partners called the misses "not an absence of protection" and said the stricter standard sets "a new competitive moat." Before the readout, Bank of America had moved its launch assumption to 2029.
Two readings
The bullish reading is that Vaxcyte passed 95% of its hardest comparisons on a margin tougher than the industry norm, clearing a path into the adult market.
The cautious reading is that the open questions now sit with the regulator, on the two serotypes the company itself expects reviewers to focus on, with a filing not planned until the first half of 2028.
The next markers
A full OPUS-1 presentation, the OPUS-2 and OPUS-3 results and any FDA view on serotypes 3 and 12F come next. Vaxcyte raised $550 million in January at $50 a share, so the price of any new offering would also be a signal.