For the second time in five weeks, the FDA has approved a new pneumococcal vaccine, this time giving the nod to a shot from Merck.
The vaccine, Vaxneuvance, is designed to protect against 15 strains of pneumococcal bacteria. That’s two more strains than Prevnar 13, a product sold that generates more than $5.8 billion in annual sales for rival Pfizer. But the total number of strains covered by Vaxneuvance is five shy of Prevnar 13’s successor, Prevnar 20, which the FDA approved in June.
These vaccines protect against pneumococcal infections, which are caused by the Streptococcus pneumoniae bacteria. Young children and the elderly are particularly susceptible to these bacteria, which can lead to infections such as pneumonia and meningitis. Infections in parts of the body that are usually free from germs can cause invasive pneumococcal disease (IPD). According to Kenilworth, New Jersey-based Merck, about 80% of all IPD that occurs is in those 50 and older.
There are more than 90 pneumococcal strains; drug companies have been working to develop vaccines capable of protecting against more and more of them. Like the Prevnar vaccines, Vaxneuvance is a conjugate vaccine. The antigens for the vaccine are polysaccharides, chains of sugar molecules from the outer bacterial coat. These chains are bonded to a carrier protein. The more polysaccharides bonded to the protein, the more strains the vaccine can protect against.
Merck tested Vaxneuvance in seven randomized, double-blind Phase 2 and 3 clinical trials. Those studies were not placebo controlled. For some diseases, it’s not ethical to assign patients to receive no treatment, so an experimental therapy is compared against an existing one. Vaxneuvance was tested against Pfizer’s Prevnar 13, evaluating it against the 13 strains shared by both of them. Results showed that Vaxneuvance was “non-inferior,” the jargony way of saying it was no worse than the Pfizer shot. The most commonly reported side effects in the study included injection site pain, fatigue, muscle pain, and headache.
The clinical studies were not designed to assess Vaxneuvance’s clinical efficacy compared to Prevnar 13. But in one of the strains, serotype 3, Merck said the immune response to its vaccine was superior to Pfizer’s. Merck added that serotype 3 is the leading cause of IPD in adults in the U.S.
Approval of Vaxneuvance covers use of the vaccine in adults 18 and older. Tests of the shot are still ongoing in healthy infants, children, and teens.
The Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices is expected to meet in October to discuss and make recommendations on the use of the newly approved Merck and Pfizer pneumococcal vaccines. The commercial market isn’t the only place where the two vaccines will clash. Merck said it has been challenging several Pfizer patents relating to pneumococcal vaccine technology.
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