Question: how long has ppsv23 been available?
Answer: The first pneumococcal vaccine, licensed in 1977, was a polysaccharide vaccine. It contained purified capsular polysaccharide antigen from 14 different types of pneumococcal bacteria. In 1983, a 23-valent polysaccharide was licensed (PPSV23; Pneumovax, Merck).