Merck & Co raises pressure on Pfizer in pneumococcal vaccine tussle

Just a month after getting approval for its new pneumococcal vaccine Vaxneuvance in adults, Merck & Co has reported positive trial results in children that will ramp up the pressure on Pfizer and its market-leading Prevnar franchise.

The 15-valent conjugate vaccine was at least as effective as Pfizer's 13-valent Prevnar 13 in the study, which involved infants up to 15 months old, and will form the basis of regulatory filing to extend the label for Vaxneuvance later this year, according to Merck.

The pharma's new vaccine was significantly more effective against one Streptococcus pneumoniae strain out of the 13 it shares with Prevnar-13 – serotype 3 – with the added bonus of covering two additional strains – known as 22F and 33F – that don't feature in Pfizer's jab.

Merck, known as MSD outside the US and Canada, got approval for Vaxneuvance from the FDA in July – a month after Pfizer upped the ante in the competitive stakes with a green light for Prevnar-20, which covers 20 serotypes, also in the over-18s.

The Centers for Disease Control and Prevention (CDC) is scheduled to review both the two new vaccines in October and decide how they should be used in adults.

Prior to COVID-19, pneumococcal vaccines were the largest vaccine market worldwide – estimated at around $8 billion – with Prevnar 13 capturing almost $6 billion of that last year from its use in both the adult and paediatric categories.

While it will have a big task taking on the established Prevnar franchise in the adult population, Merck has an opportunity to steal a march on Pfizer in the large paediatric pneumococcal vaccine category, as its rival is around a year away from reporting results with Prevnar-20 in children.

Children under the age of two are particularly vulnerable to pneumococcal infection, and incidence of invasive pneumococcal disease remains highest in the first year of life, according to Merck.

Serotypes 3, 22F, and 33F account for more than a quarter of all cases of invasive pneumococcal disease in children under the age of five, providing a reason to vaccinate with Vaxneuvance over Prevnar-13.

Prevnar-20 covers those three, plus another five (serotypes 8, 10A, 11A, 12F and 15B), and Pfizer says the 20 included in the shot are responsible for the majority of currently circulating pneumococcal disease in adults in the US and globally.

Merck already sells an older pneumococcal vaccine called Pneumovax 23, which protects against 23 strains but is a polysaccharide based shot, so doesn't stimulate as strong an immune response as the conjugate jabs. It is mainly oriented towards adults, a smaller target population than children who account for around 80% of the market.

Meanwhile, Merck is also working on two follow-up conjugate vaccines – V116 and V117 – that will extend its range. V116 is a specifically targeting adult disease, and the most common serotypes that cause disease in older people based on epidemiological data, while V117 is taking the same approach for the paediatric population.

Another rival – Affinivax – recently reported phase 2 data with a new 24-valent pneumococcal vaccine, partnered with Astellas, that it thinks could challenge the established companies.

"By nature, pneumococcal disease is constantly evolving," said Merck chief medical officer Dr Roy Baynes.

"Strains of the disease associated with invasiveness cause significant disease burden in children, calling for innovation to help protect this vulnerable population worldwide," he added.