Immunogenicity, reactogenicity and safety of the human rotavirus vaccine RIX4414 (Rotarix™) oral suspension (liquid formulation) when co-administered with expanded program on immunization (EPI) vaccines in Vietnam and the Philippines in 2006-2007.

Evaluation of immunogenicity and safety of a 2-dose liquid formulation of human rotavirus vaccine, RIX4414 following WHO's Expanded Program on Immunization (EPI) schedule (0, 1, and 2 months; Month 0 indicates day of enrollment) in Vietnam and the Philippines. Infants aged 6-10 (mean=8.7 ± 1.07 weeks Vietnam) and 5-10 weeks (mean=6.6 ± 1.03 weeks Philippines) received two doses of RIX4414 vaccine (V) and one dose of placebo (PL) or three placebo doses concomitantly with commercially available diphtheria-tetanus-whole-cell pertussis, hepatitis B and oral poliovirus vaccines. The vaccination schedules were: V-V-PL, V-PL-V and PL-PL-PL (Vietnam); PL-V-V, V-PL-V and PL-PL-PL (Philippines). Anti-rotavirus seroconversion rate was assessed pre-vaccination and post-vaccination (ELISA cut-off=20 U/ml). 375 infants were enrolled in each country. Seroconversion rates at one month post-Dose 2 of RIX4414 were Vietnam 63.3% (95% CI: 54.3-71.6) in V-V-PL group and 81.5% (95% CI: 73.4-88) in V-PL-V group; Philippines 70% (95% CI: 61-78) in PL-V-V group and 59.2% (95% CI: 49.8-68) in V-PL-V group. Frequencies of solicited (8-day post-each dose) and unsolicited symptoms (31-day post-each dose) were similar. Two-doses of rotavirus vaccine administered within the WHO EPI offer flexibility in existing schedule, though both schedules provides good immune responses.

Immunogenicity and adverse effects of live attenuated varicella vaccine (Oka-strain) in children with chronic liver disease.

Varicella infection may cause significant morbidity and mortality especially in immunocompromised persons. Children with chronic liver disease who undergo liver transplantation and need long term immunosuppressive therapy are at risk to acquire the infection. Twenty-nine children (aged 1-12 years) with chronic liver disease were enrolled to receive one dose of live attenuated varicella vaccine (Oka-strain). During the 16-week follow-up period, no vaccine-related serious adverse events were reported. Seroconversion rates at 8 weeks post vaccination were 100%. Geometric mean titer (GMT) values and seropositive rates at 16 weeks tended to relate to the clinical severity of liver disease. This study demonstrates that varicella vaccine is safe and Immunogenic in children with chronic liver disease.

Effect of climatic factors and population density on varicella zoster virus epidemiology within a tropical country.

Blood samples were collected from healthy subjects, aged 9 months-29 years in urban and rural communities from 4 distinct regions in Thailand, to determine the seroprevalence rate of varicella-zoster virus (VZV) antibody and its relationship with demographic, climatic, and socioeconomic factors. The overall seroprevalence rate was 52.8% and increased from 15.5% in the 9-month to 4-year-old group to 75.9% in the 20-29 year-olds. The age-adjusted seroprevalence was significantly higher in the cooler than in the warmer regions. In the warmer regions only, the age-specific seroprevalence was significantly higher in the urban population than in the rural population. In Thailand, climate is the main determinant of VZV seroprevalence. The delayed onset of natural immunity is more marked in warmer climate areas. Population density is a secondary determinant; in the warmer areas, the pattern of adolescent and adult susceptibility was greater in rural than in urban areas.