For the second time in five weeks, the FDA approved a new pneumococcal vaccine, this time okaying a shot from Merck.
The vaccine, Vaxneuvance, is designed to protect against 15 strains of pneumococcal bacteria. That’s two more varieties 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 fewer than Prevnar 13’s successor, Prevnar 20, which the FDA approved in June.
These vaccines protect against pneumococcal infections, which are caused by the bacteria Streptococcus pneumoniae. 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 generally germ-free can cause invasive pneumococcal disease (IPD). According to Kenilworth, NJ-based Merck, about 80% of all IPD cases that occur occur in people age 50 and older.
There are more than 90 pneumococcal strains; Pharmaceutical 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 in the vaccine are polysaccharides, chains of sugar molecules from the outer bacterial coat. These chains are attached to a carrier protein. The more polysaccharides that bind to the protein, the more strains the vaccine can protect.
Merck tested Vaxneuvance in seven randomized, double-blind phase 2 and 3 clinical trials. Those studies were not placebo controlled. For some diseases, it is unethical to assign patients to receive no treatment, so an experimental therapy is compared to an existing one. Vaxneuvance was tested against Pfizer’s Prevnar 13, evaluating it against the 13 strains shared by both. The results showed that Vaxneuvance was “not inferior,” the jargon of saying it was no worse than the Pfizer shot. The most frequently reported side effects in the study included injection site pain, fatigue, muscle pain, and headache.
The clinical studies were not designed to evaluate the clinical efficacy of Vaxneuvance compared to Prevnar 13. But in one of the strains, serotype 3, Merck said the immune response to its vaccine was superior to that of Pfizer. Merck added that serotype 3 is the leading cause of IPD in adults in the US.
Vaxneuvance approval covers the use of the vaccine in adults 18 years of age and older. Vaccine testing is still on going in healthy babies, children and adolescents.
The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention is expected to meet in October to discuss and make recommendations on the use of the newly approved pneumococcal vaccines from Merck and Pfizer. The commercial market is not the only place where the two vaccines will collide. Merck said it has challenged several Pfizer patents related to pneumococcal vaccine technology.
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