Age Factors Child, Preschool Drug Resistance, Microbial Humans Malaysia Middle Aged Penicillin Resistance Pneumococcal Vaccines Pneumococcus vaccine Prevalence Serotyping Streptococcus pneumoniae Vaccines, Conjugate age antibiotic resistance antibiotic sensitivity article bacterial strain bacterium isolate controlled study drug effect drug efficacy human immunology infection risk isolation and purification middle aged minimum inhibitory concentration multiplex polymerase chain reaction nasopharynx