Epidemiologic Characteristics of Streptococcus pneumoniae in Vietnam and Implications for Population Vaccination.

Abstract

Streptococcus pneumoniae is the leading cause of bacterial infections worldwide and causes a range of illness from otitis media to pneumonia and meningitis. Use of the heptavalent pneumococcal conjugate vaccine (PCV7) in the United States led to a reduction in invasive pneumococcal disease caused by vaccine serotypes (VTs), reduced nasopharyngeal (NP) carriage of VTs, and reduced antibiotic-resistant pneumococcal disease. However, an increase in colonization and disease due to non-vaccine serotypes has been observed and may threaten the long-term utility of this vaccine. Other countries now want to introduce a PCV. Vietnam, in particular, would like to introduce a PCV, but the epidemiologic data upon which to base this decision are lacking. In order to provide Vietnamese health policymakers with the data upon which to base a decision about a pneumococcal vaccine and to more broadly advance the understanding of the epidemiology of S. pneumoniae, we conducted a cross-sectional study of NP carriage among 519 healthy individuals of all ages who lived in 115 households in one hamlet of Nha Trang, Vietnam. NP carriage was common among children (40%), and colonization decreased with age to 2% among adults ≥ 50 years. Children ≤5 years were more likely to carry PCV serotypes, while older children and adults were more likely to carry non-PCV serotypes. The prevalence of multidrug resistance was high among PCV and non-PCV serotypes (83%). We also identified an unusually high proportion of nontypeable (NT) pneumococci colonizing children and adults in Vietnam (30% of isolates). These NTs were more likely to be resistant compared to encapsulated pneumococci. Furthermore, we demonstrated that a multiplex PCR assay for capsular typing of invasive isolates can also be used with carriage isolates. Finally, we identified age as the most important predictor of individual- and household-level pneumococcal colonization. Children in Vietnam may greatly benefit from use of a PCV, although a vaccine may not reduce antibiotic resistance in Vietnam in the long-term because of the high prevalence of resistance among non-PCV serotypes and the low probability of decreases in inappropriate antibiotic usage in Vietnam.