Is Pfizer’s pneumococcal dominance under threat?

News of a stumble in a crucial paediatric trial of Pfizer’s latest pneumococcal vaccine, Prevnar 20, made for worrying reading last week. Six viral serotypes failed to meet non-inferiority on one of the co-primary endpoints of a US pivotal trial, two by a wide margin and four narrowly, the group said on Friday. Without knowing which serotypes were at fault it is hard to judge the significance; SVB wrote that if these strains were not already covered by Merck & Co’s rival 15-valent shot, Vaxneuvance, and/or were not associated with invasive disease, Prevnar 20 should still have a chance to compete. Vaxneuvance won its paediatric approval last month, and Pfizer needs to defend the dominance of earlier Prevnar iterations. A further observation by SVB gives further reason for pessimism, however. Last month Pfizer started a phase 1 trial testing six new pneumococcal vaccine candidates that look to have fewer strains than Prevnar 20. Being able to maintain ironclad protection while expanding a vaccine's coverage has always been the challenge in this space, and perhaps Pfizer is also preparing for more Prevnar 20 disappointment. Either way, all eyes now turn to the next pivotal readout, due before year end.