Abstract: A shortened process for producing a solution containing substantially purified capsular polysaccharides from a cellular Streptococcus pneumoniae lysate broth is described. Ultrafiltering and diafiltering a clarified S. pneumoniae lysate followed by pH adjustment to less than 4.5, preferably about 3.5, precipitated at least 98% of the protein in the solution without seriously affecting polysaccharide yield. Furthermore, following ultrafiltration and diafiltration and acidification to a pH of less than 4.5, filtration using activated carbon precipitated at least 90% of remaining protein without seriously affecting polysaccharide yield. Exemplary, non-limiting S. pneumoniae serotypes that can be purified using the shortened process of the invention are 1, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F.