Strains of drug-resistant S. pneumoniae have become increasingly common in China and in other parts of the world. In some areas as many as 35% of pneumococcal isolates have been reported to be resistant to penicillin. Many penicillin-resistant pneumococci are also resistant to other antimicrobial drugs (e.g., erythromycin, trimethoprim-sulfamethoxazole and extended-spectrum cephalosporins), therefore the importance of vaccine prophylaxis should be emphasized against pneumococcal disease.