Both of my sons received the first vaccination at their nine month check-up and the second six weeks later. I happy to say that there were no side effects from either one. Our Ped highly suggested the vaccine. However, she said that it does not necessarily prevent ear infections. It is used to prevent pneumococcal diseases caused by steptococcus pneumoniate - like meningitis. It is not the same kind of strep that one gets in the throat. About 6 months ago a young girl in our area died from this disease. Supposedly, many of these bacterias are resistance when treated with antibiotics. Thats why she felt that the vaccine was such a good idea. Hope this helped:)