Vaxcyte Stock Surges After Pneumonia Vaccine Trial Success

Vaxcyte’s experimental pneumococcal vaccine, VAX-31, achieved strong results in a late-stage trial, surpassing expectations and sending the company’s stock soaring. In the OPUS-1 study, VAX-31 matched or outperformed immune responses from Pfizer’s Prevnar 20 and Merck’s Capvaxive on most strains, while also showing superior responses against three unique strains. The trial, involving over 4,000 healthy adults, met all primary immunogenicity targets in adults 50 and older and successfully bridged to younger adults. Side effects were mild to moderate, with no serious adverse events reported.

Shares of Vaxcyte (PCVX) jumped more than 60% on Monday after the positive trial results, hitting a fresh 52-week high of $90.75 before paring back some gains. The stock was up 29% at the time of writing, on track for its best day since September 2024. CEO Grant Pickering described the data as a new benchmark for the class, setting the stage for a biologics license application. The company plans to file for adult approval in the first half of 2028, with additional trial results expected in the first half of 2027.

Analysts praised the results, calling them stellar and exceeding expectations. Jefferies analyst Roger Song described the outcome as a blue-sky scenario, supporting approval and positioning VAX-31 to capture a significant share of a growing adult pneumococcal market valued at $3 billion to more than $6 billion. Mizuho and Guggenheim also expressed bullish views, with Guggenheim raising its target to $125 and maintaining a ‘Buy’ rating.

Retail sentiment around PCVX stock shifted from neutral to extremely bullish, with message volume rising to extremely high levels on Stocktwits. The stock has gained 58% year-to-date, reflecting investor enthusiasm for the company’s promising vaccine candidate.