Immunization with pneumococcal conjugate vaccine reduces drug-resistant cases of pneumococcal diseases in children and adults

Studies in several countries have shown that, following the introduction of pneumococcal conjugate vaccine, there was a reduction in the number and percent of drug-resistant cases of pneumococcal diseases in children, and in some countries in adults, due to herd effects. In Japan there was a 10-fold decline in the proportion of penicillin-resistance among cases of invasive pneumococcal disease (from 56% to 5%), and in the U.S. there were reductions of 81% and 49% in the proportion of penicillin-resistant cases in children less than two years and in adults more than 65 years old, respectively.