ABSTRACT
Objective: To investigate the long-term safety of a tetravalent dengue vaccine (CYD-TDV) in children in a phase Π b follow-up study in Thailand. Methods: In the phase Π b study, children aged 4-11 years were randomized (2:1) to receive three injections of CYD-TDV or serve as control at 6-month intervals, with 25 months' active follow-up (active phase). This study was an additional four-year passive surveillance for hospitalized virologically-confirmed dengue (VCD; hospital phase). Cases of hospitalized VCD, severe hospitalized VCD, vaccine-related serious adverse events, and deaths were reported for the total population, with post-hoc analyses by enrollment age (<9 and years). Results: Of 3 997 participants receiving injection, 80.1% were recruited to the hospital phase [2 131 (CYD-TDV); 1 072 (control)]. Eighty-five hospitalized VCD cases were reported in the CYD-TDV group and 46 in the control group during the four-year hospital phase [relative risk (RR): 0.93, 95% confidence interval (CI): 0.64-1.36]. The RR over six years of follow-up was 0.77 (95% CI: 0.57-1.05). In those aged ≥9 years, the cumulative RRs in the active phase, hospital phase, and entire six years were 0.28 (95% CI: 0.08-0.81), 0.51 (95% CI: 0.25-1.05), and 0.42 (95% CI: 0.24-0.75), respectively. In the overall population, there were ten severe hospitalized VCD cases in the CYD-TDV group and five in the control group over six years (RR: 1.00, 95% CI: 0.31-3.75). Conclusions: Over six years of follow-up, in children aged ≥9 years, CYD-TDV administration is associated with a reduced risk of hospitalized VCD.
ABSTRACT
Streptococcus pneumoniae (S. pneumoniae) is the major pathogen that causes health problems worldwide. Invasive disease includes meningitis, bacteremia with or without focus and pneumonia. It causes morbidity and mortality, especially in children. In Thailand, no relevant study was done to estimate the exact incidence of invasive pneumococcal diseases. Serotypes, in children with invasive diseases, differ slightly by age; less than five years old: serotype 23F, 6B, 14, 9V, and 19F, more than five years old: serotype 4, 23F, 19F, and 9V, while the most frequent serotypes in nasopharyngeal specimens are serotype 6B, 19F, 23F, and 14. The prevalence and the level of drug resistance of S. pneumoniae (DRSP) have been increasing. A significant risk factor for S. pneumonia infections is previous antibiotic use within three months. Seven-valent pneumococcal conjugate vaccine can prevent 73.9% of the most common pneumococcal serotypes in children younger than five years of age. There is a need for cost-effectiveness studies for inclusion of this vaccine in the national children immunization programme.