Vaxcyte Stock Jumps 31% on Promising Pneumococcal Vaccine Trial Results

Vaxcyte's stock surged 30.7% to close at $73.82 after its experimental pneumococcal vaccine, VAX-31, successfully completed all primary endpoints in a late-stage trial. The shares briefly hit $90.75 during trading but pared gains after the company announced a $1 billion equity-linked financing round.

The OPUS-1 trial results suggest VAX-31 could challenge Pfizer’s Prevnar 20 and Merck’s Capvaxive. VAX-31 targets 31 serotypes, more than either competitor. The study enrolled 4,047 adults, with over 3,500 participants aged 50 or older randomized to receive VAX-31 or a comparator vaccine.

While VAX-31 met all noninferiority criteria for serotypes shared with Prevnar 20, it missed the threshold for serotypes 3 and 12F when compared to Capvaxive. However, the company maintained that all primary endpoints were achieved under the trial’s pooled comparison structure. Safety results were comparable to existing vaccines, with most reactions mild and no serious adverse events linked to the study vaccines.

Analysts praised the results, with Jefferies' Roger Song noting they matched the firm’s upside scenario. Leerink Partners' David Risinger downplayed the serotype 3 miss against Capvaxive, suggesting it was unlikely to impact regulatory approval. Vaxcyte plans to submit its US biologics application in the first half of 2028, pending further trial results.

After market close, Vaxcyte launched offerings totaling $1 billion in common stock, pre-funded warrants, and convertible senior notes. The company aims to fund remaining trials, manufacturing, and commercial preparation. The stock’s retreat from its intraday high reflected investor awareness of the significant capital still needed before launch.