FDA clears Pfizer's Prevnar 20 for adults, as Merck rival nears decision

Pfizer has the FDA approval it was seeking for Prevnar 20, the latest update to its blockbuster pneumococcal vaccination franchise, keeping it one step ahead of a competing shot from Merck & Co.

The US regulator has cleared the pneumococcal conjugate vaccine – which protects against 20 common strains of Streptococcus pneumoniae – for adults aged 18 or older, and it now goes to the Advisory Committee on Immunization Practices (ACIP) for a decision on how it should be used in practice.

Pneumococcal disease is caused by Streptococcus pneumoniae, and includes non-invasive illnesses like pneumonia, sinusitis and middle ear infections, as well as invasive diseases like meningitis.

Prevnar covers all 13 serotypes found in Pfizer's near-$6 billion Prevnar 13 product, plus another seven that are linked to invasive pneumococcal disease (IPD) and have been associated with high fatality rates, antibiotic resistance and meningitis.

All told, the 20 serotypes covered by the new vaccine account for more than half of the 250,000 cases of IPD reported each year in the US, according to Pfizer.

"Overall, the seven additional serotypes in Prevnar 20 account for approximately 40% of all pneumococcal disease cases and deaths in the US," said the drugmaker. Around 10,000 American adults a year die as a result of IPD.

Prevnar 20 is also being developed for use in children, where Prevnar 13 is a mainstay of routine vaccination schedules in the US, although that programme is further back in development isn't expected to be ready for market until early 2023.

Growth of Prevnar has been driven lately by use in adults, however, and it is here that Pfizer is facing a challenge from Merck and its V114 pneumococcal conjugate vaccine candidate.

The Prevnar 20 approval comes a few weeks ahead of an FDA decision on Merck's V114, which was granted a priority review by the regulator in January for the prevention of IPD in adults.

V114 covers 15 serotypes, so the jury is out on whether it will be a big challenger to Pfizer's well-established brand now that Prevnar 20 is becoming available.

In two phase 3 trials in adults reported last year, V114 stimulated immune responses to all serotypes in the shot. The studies included a booster shot with Merck's older polysaccharide-based Pneumovax 23 vaccine, which is still widely used in elderly people, and showed that the combination was protective in both the over-50 and under-50 adult age groups.

Merck seems to be a little ahead of Pfizer in the paediatric setting however, with a filing anticipated by the end of the year, setting up a possible approval and launch for V114 in children a few months earlier than Prevnar 20.

Also emerging from the wings is Vaxcyte, which has a 24-valent shot in early development and hopes to have initial clinical data from that programme in late 2022/early 2023.