I didn't realize that the pfizer and merck vaccines have a bunch of non-overlapping serotype coverage. Per the PR MRK's covers 8 serotypes that are unique, so that means prevnar 20 has at least 7 serotypes that MRK's doesn't contain What I don't know is which vaccine provides better coverage overall, and you have to factor in the fact that there is selective pressure for pneumonia from serotypes that aren't covered currently so the coverage is likely to evolve over time actually