This article is from the Childhood Vaccinations FAQ, by Lynn Gazis-Sax firstname.lastname@example.org with numerous contributions by others.
It protects against 23 strains of pneumococcus, 85% of those which
cause ear infections and almost all of those which cause pneumonia and
meningitis. Harrison's Internal Medicine estimates its effectiveness
Some recent articles discussing (and debating about) the effectiveness
of pneumococcal vaccine can be found in Arch Intern Med 1994 Dec;
154:373, 154:2666 and 154:2531; these articles and others are
summarized in "Feature: Does Pneumococcal Vaccine Live Up to Its
Reputation?" in the February 28, 1995 Journal Watch (electronic form)
or Mar 1, 1995 Journal Watch (print form). Other relevant articles are
in the Annals of Internal Medicine 1988;108:616-625 and the New
England Journal of Medicine for 11/21/91.