Vaxcyte's (PCVX) upcoming data readout for its investigational pneumococcal conjugate vaccine VAX-31 is set to be a "major catalyst" for the company, with the vaccine positioned to validate broad coverage, BofA Securities said in a Monday note.

Top-line data from the phase 3 OPUS-1 trial of VAX-31 is expected in Q4, according to the note.

The brokerage estimates a 75% probability of clinical success. The phase 3 trial, however, adds risk to VAX-31's "essentially flawless" phase 2 data on adults with its more rigorous design that was developed with the US Food and Drug Administration.

The phase 3 trial adds Capvaxive as a second comparator, with a tighter non-inferiority margin, though VAX-31 only needs to demonstrate non-inferiority against one comparator on shared serotypes for the primary endpoint, the investment firm said.

VAX-31's comparison with Prevnar-20 should be largely de-risked, with the vaccine potentially missing on one shared serotype, but could miss on three to six shared serotypes in comparison with Capvaxive.

BofA Securities reiterated its buy rating on Vaxcyte and cut its price target to $130 from $133.

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