By Vaxcyte stock closed 30.7% higher at $73.82 after its experimental pneumococcal vaccine met every prespecified primary endpoint in a pivotal late-stage trial. The shares reached $90.75 during the session before giving back more than half of the intraday gain, then weakened further after the clinical-stage company launched $1 billion of equity-linked financing.
The OPUS-1 results improved the probability that VAX-31 can become a competitor to Pfizer’s Prevnar 20 and Merck’s Capvaxive. They did not establish regulatory approval or show directly that the vaccine prevents more real-world cases of pneumonia.
VAX-31 Covers More Serotypes
Pneumococcal vaccines target serotypes of Streptococcus pneumoniae that can cause pneumonia, meningitis and bloodstream infections. VAX-31 covers 31 vaccine serotypes, compared with 20 for Prevnar 20 and 21 for Capvaxive.
OPUS-1 enrolled 4,047 adults. More than 3,500 participants aged 50 or older were randomized to receive VAX-31 or one of the two marketed comparators, while a younger cohort supported immunobridging across age groups.
For the 28 VAX-31 serotypes shared with at least one comparator, all met the study’s prespecified noninferiority criterion when the relevant Prevnar 20 or Capvaxive comparison was used. The three serotypes unique to VAX-31 and cross-reactive serotype 20B met the superiority criterion.
Two Capvaxive Comparisons Need Context
The detailed comparator analysis was less uniform than the all-endpoint headline. VAX-31 met the stricter noninferiority threshold for all 20 serotypes it shares with Prevnar 20, but for 17 of 19 shared with Capvaxive. Serotypes 3 and 12F missed the prespecified lower-confidence-bound threshold of 0.667 against Merck’s vaccine.
Both cleared the historical threshold of 0.5. That allowed Vaxcyte to report that all primary endpoints were achieved under the trial’s pooled comparison structure, while still disclosing the two misses in the individual Capvaxive analysis. Investors will need the full dataset and regulatory feedback to determine whether those serotypes affect labeling or review.
Safety results were comparable with the marketed vaccines. Most solicited reactions were mild or moderate and resolved within 48 hours, according to Vaxcyte. The company reported no serious adverse events considered related to the study vaccines and no discontinuations caused by adverse events.
Pfizer and Merck Face a Broader-Spectrum Challenger
The commercial case rests on breadth. Vaxcyte estimates VAX-31 could cover 95% of invasive pneumococcal disease and 88% of pneumococcal pneumonia among US adults aged 50 and older. Those are modeled coverage estimates based on circulating serotypes, not observed efficacy rates from OPUS-1.
Jefferies analyst Roger Song described the results as reaching the firm’s upside scenario and said the candidate could take a material share of the adult pneumococcal market. Leerink Partners analyst David Risinger argued that the serotype 3 miss against Capvaxive came from a demanding comparison and was unlikely to be significant for regulators.
Vaxcyte still needs results from OPUS-2, which studies administration with a seasonal influenza vaccine, and OPUS-3 in adults previously vaccinated against pneumococcal disease. Both readouts are expected in the first half of 2027. The company plans to submit its US biologics application in the first half of 2028.
Vaxcyte Used the Rally to Raise Capital
After the market closed, Vaxcyte launched two separate offerings. One covers $500 million of common stock and pre-funded warrants. The other covers $500 million of convertible senior notes due in 2032.
Underwriters may buy up to another $75 million of shares and $75 million of notes, taking potential gross proceeds to $1.15 billion. The equity portion creates direct dilution, while the notes may be settled in cash, shares or a combination and therefore carry possible future dilution.
Vaxcyte plans to fund the remaining adult and pediatric trials, manufacturing capacity, inventory and commercial preparation. The timing is rational for a company with no approved product: a positive pivotal result lowered clinical risk and raised the price at which it could sell equity. It also explains why the stock retreated from its intraday high. Investors received stronger evidence for VAX-31 and an immediate reminder of how much capital is still required before launch.