Epidemiological knowledge gaps
From this analysis, it is clear that recent improvements in the national surveillance system have contributed to an improvement in epidemiological knowledge in Malaysia. Nevertheless, some gaps in epidemiological knowledge still exist; for example, there is a lack of data on age-stratified seroprevalence , long-term regional incidence and serotype distribution, relationships between age and disease severity, and hospital admissions. Furthermore, the national surveillance data are likely to have underestimated the true incidence of the disease in Malaysia owing to the use of a passive reporting system and low levels of reporting from private or primary care [10]. In addition, further investigations are required to examine the reasons for epidemiological patterns that