15-valent pneumococcal vaccine shows promise in children in phase 3 trials
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Merck’s investigational V114 pneumococcal conjugate vaccine, which includes 15 serotypes, met its primary immunogenicity and safety endpoints in two phase 3 pediatric trials, the company announced.
Merck has already submitted the vaccine to the FDA for priority review for use in adults, with a decision expected by July 18. Pending that decision, Merck said it plans to submit a supplementary regulatory licensure application to the FDA for use in children by the end of the year.
“Pneumococcal disease continues to cause serious illness and death worldwide in children under the age of 5, despite the positive impact of pneumococcal conjugate vaccination on pediatric case numbers,” Roy Baynes, MD, PhD, head of global clinical development and chief medical officer for Merck, said in a new release. “Our goal is to expand coverage to new serotypes not targeted by currently available pediatric pneumococcal conjugate vaccines, while maintaining a strong immune response to current vaccine serotypes so as to help sustain progress achieved to date.”
According to the news release, data from the trials support the use of V114 in healthy infants who have already started a pneumococcal vaccination series with the currently available 13-valent pneumococcal conjugate vaccine (PCV13), or in a catch-up setting for healthy children who have not received a pneumococcal vaccine or who already received a full or partial regimen with lower valency pediatric pneumococcal conjugate vaccines.
In a study of infants aged 42 to 90 days, “immune responses in those who received a four-dose series of PCV13, and those who received a mixed dose schedule of PCV13 followed by V114, were generally comparable for the 13 serotypes, or strains of pneumococcal disease, targeted by both vaccines,” Merck said.
In a catch-up study, immune responses were comparable to PCV13 for the 13 shared serotypes when V114 was used as a catch-up regimen in healthy children aged 7 months to 17 years, who were either pneumococcal vaccine-naive or who previously received a partial or full regimen of a licensed pediatric PCV, according to the company.
In two serotypes included in the V114 vaccine but not the PCV13 — 22F and 33F — immunogenicity was higher in the V114 group than in the PCV13 group, the company reported.
Full results from both trials will be presented a future meeting, Merck said.
Perspective
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There is a 20-valent version of the conjugate vaccine that's likely to be approved relatively soon, as well. There's uncertainty about for whom these are going to be targeted. So, on the one hand, it is a good thing to have vaccines that cover more serotypes. Although, there are issues because serotype replacement can occur. And it's not clear yet what the best strategy is, and it will have a lot to do with dosing strategies and with costs.
The vaccines are very safe, so safety isn't an issue. It's possible that both of the new conjugate vaccines will be approved, and authorities will say, “well, you can use the PCV13, or PCV15 or the PCV20.” A lot of it has to do with the indirect effects on adults, because what's important to realize is that by immunizing children, you protect adults, because children are the major reservoir, they are vectors for disease in adults.
When PCV7 first came out, invasive disease due to those serotypes in children went down 98%. It went down 92% in adults aged over 65 years, even though they didn't get the vaccine.
So, the problem is that in adults, a certain proportion of the disease that is prevented by giving the conjugate vaccine to children is replaced by other serotypes not in the vaccine. So, I think it's not completely clear yet, for whom these are going to be recommended, or how they're going to be used. It's certainly not a bad thing, but it's going to have a lot to do with costs.
Eventually, it’s likely there may be different vaccine formulations for adults and children. It may be better, for example, to give children PCV13 and adults PCV20. I'm not suggesting that that's what the recommendation will be, but I'm just saying that it may be a completely different formulation, specifically targeting adults for the types that may become important for disease.
There are a couple of serotypes for which even the current vaccine has not been effective. Namely, serotype 3, even though it is included in PCV13. A lot of the residual disease in the U.S. is due to serotype 3 and whether that is actually a question of immunogenicity or because serotype 3 has a very thick mucoid capsule and it sheds that capsule periodically and it may be that even though you have the antibodies that attach, it may shed and so the antibodies may not be as effective. Or, perhaps higher titers with new vaccines might make a difference. I think there are a lot of unknowns still
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