Three Decades of Dengue Surveillance in Five Highly Endemic South East Asian Countries.

We described and quantified epidemiologic trends in dengue disease burden in 5 Asian countries (Indonesia, Thailand, Malaysia, Philippines, and Vietnam) and identified and estimated outbreaks impact over the last 3 decades. Dengue surveillance data from 1980 to 2010 were retrieved from DengueNet and from World Health Organization sources. Trends in incidence, mortality, and case fatality rate (CFR) were systematically analyzed using annual average percent change (AAPC), and the contribution of epidemic years identified over the observation period was quantified. Over the 30-year period, incidence increased in all countries (AAPC 1980-2010: 6.7% in Thailand, 10.4% in Vietnam, 12.0% in Indonesia, 18.1% in Malaysia, 24.4% in Philippines). Mortality also increased in Indonesia, Malaysia, and Philippines (AAPC: 6.8%, 7.0%, and 29.2%, respectively), but slightly decreased in Thailand and Vietnam (AAPC: -1.3% and -2.5%), and CFR decreased in all countries (AAPC: -4.2% to -8.3%). Epidemic years, despite representing less than a third of the observation period, contributed from 1 to 3 times more cases versus nonepidemic years. Implementation of more sensitive surveillance methods over the study period may have contributed to a reporting or ascertainment bias in some countries. Nonetheless, these data support the urgent need for novel, integrated, or otherwise effective dengue prevention and control tools and approaches.

Pre-discharge immunization among hospitalized Filipino children.

Identifying opportunities to vaccinate eligible children is one way to boost rates of immunization especially in countries with low immunization coverage and where convalescence from infectious illness is a contraindication to vaccination. To determine the safety and immunogenicity of diphtheria-tetanus toxoid-pertussis and oral polio immunization, 210 convalescing infants and children and community controls, comparable image and nutritional status, were studied. Using the pertussis agglutination and poliovirus neutralization tests, quantitative serologic responses were compared in the two study groups. No significant differences in the incidence rates of febrile reactions (23% in controls; 28% in convalescents) of local reactions (92% in controls; 87% in convalescents) and of seroconversion (P greater than 0.05) were noted between the two groups. Our investigation suggests that infants and children convalescing from infectious illnesses can be safely and effectively vaccinated. This study further suggests that hospitalization provides an opportunity to vaccinate such children.

Effect of transplacentally acquired tetanus antibodies on the antibody responses to Haemophilus influenzae type b-tetanus toxoid conjugate and tetanus toxoid vaccines in Filipino infants.

BACKGROUND: Pregnant women in developing countries are vaccinated with tetanus toxoid (TT) to prevent neonatal tetanus. In populations in which the maternal TT-vaccination program is efficiently implemented, responses of the infant to TT and TT-conjugated vaccines such as Haemophilus influenzae type b (Hib) capsular polysaccaride (PS) TT-conjugate (Hib-TT) vaccine may be depressed. OBJECTIVES: To study the influence of transplacentally acquired anti-TT antibodies on responses to TT vaccination and to Hib-TT vaccine. METHODS: One hundred ninety-four healthy Filipino infants received three doses of a Hib conjugate (either Hib-TT, PRP-OMP or HbOC) with diphtheria-tetanus-pertussis vaccine (DTP) given simultaneously but in a separate syringe at the age of 6, 10 and 14 weeks (primary series). In addition 54 of the study children received a booster dose of Hib-TT at 9 months simultaneously with the measles vaccine. RESULTS: Transplacentally acquired anti-TT did not interfere with the anti-Hib PS antibody (anti-Hib PS) response to any of the conjugates. The transplacentally acquired anti-TT was not significantly associated with the concentration of anti-Hib PS either before or after the booster dose of Hib-TT. High concentrations (> or =1 IU/ml) of transplacentally acquired anti-TT inhibited the infants' anti-TT responses. CONCLUSIONS: High concentration of transplacentally acquired anti-TT did not depress anti-Hib PS responses to the Hib-TT vaccine. On the other hand the high anti-TT concentrations somewhat depressed the anti-TT responses of the infants. However, the anti-TT concentrations attained were in the protective range in all study children after either the primary series (DTP + Hib-TT) or the booster dose of Hib-TT.

Invasive bacterial infections of children in a rural province in the central Philippines.

The etiology of invasive bacterial infections was studied among 956 Filipino children less than five years old who fulfilled the World Health Organization criteria for severe or very severe pneumonia or had suspected meningitis or sepsis. The most common invasive infections were due to Streptococcus pneumoniae (12 [1.3%]) and Haemophilus influenzae (12 [1.3%]); including four cases of pneumococcal meningitis and 11 cases of H. influenzae meningitis. Type 1 was the most common (six of the 12 isolates) of the pneumococcal serotypes. Serotypes/groups 1, 6, 14, and 23 accounted for 91.7% of the invasive isolates. The majority of the H. influenzae strains from blood (10 out of 10) and cerebrospinal fluid (6 out of 7) were type b. Almost all of the invasive S. pneumoniae (9 out of 12) and H. influenzae (11 out of 12) infections were seen before one year of age, which stresses the need to investigate early immunization of children for H. influenzae type b and S. pneumoniae, as well as maternal immunization to maximize the potential of immunoprophylaxis.

The immunogenicity of three Haemophilus influenzae type B conjugate vaccines after a primary vaccination series in Philippine infants.

Serum antibody responses to three Haemophilus influenzae type b (Hib) capsular polysaccharide-protein conjugate vaccine (PRP-OMP, PRP-T, and HbOC) were evaluated in 174 Philippine infants after a primary vaccination series. Children were randomized to receive one of the Hib vaccines (Hib groups) or into a control group. Vaccination was carried out at six, 10 and 14 weeks of age based on the local Expanded Program of Immunization schedule. Sera were collected at six weeks of age for the Hib groups and one month after the third dose for all subjects. Anti-Hib concentrations were determined by the Farr-type radioimmunoassay. There were no significant differences (P = 0.3626) in the prevaccination anti-Hib geometric mean concentration (GMC) among the three Hib groups. Differences in the GMC after the primary series of three doses were significant (P < 0.0001); GMC was highest for PRP-T (6.62 micrograms/ml), followed by HbOC (1.9 micrograms/ml), then PRP-OMP (1.06 micrograms/ml), and lowest for the control group (0.11 microgram/ml). We conclude that all three Hib conjugate vaccines (PRP-T, HbOC, and PRP-OMP) were immunogenic after three primary doses among Philippine infants.

Etiology of acute lower respiratory infection in Filipino children under five years.

This study conducted at the Research Institute for Tropical Medicine from April 1990 to December 1992, identified the etiology of acute lower respiratory tract infection (ALRI) in 119 (36.9%) of 317 hospitalized children < 5 years of age. A higher proportion of respiratory viruses (27.2%) than bacterial agents (10.7%) were identified. Viral agents (adenovirus, RSV, parainfluenza 3, influenza A and influenza B) and bacterial agents (mainly Haemophilus influenzae and Streptococcus pneumoniae) are the pathogenic agents involved in ALRI among Filipino children less than 5 years old.

Dengue surveillance in Metro Manila.

In a one-year surveillance of dengue infection in four hospitals in Metro Manila, Philippines, 143 patients were enrolled. Sixty seven were diagnosed by virus isolation and serology. Majority of patients had secondary antibody response. Only 5 patients developed dengue shock syndrome. Only dengue types 1 and type 2 were isolated. Highest incidence occurred among older children and young adults. Thrombocytopenia and hemoconcentration were observed in 37% and 77% of patients, respectively. There was no fatality. Several problems were identified in the course of the study which need to be corrected in order to have good quality surveillance data in future undertakings.

Blood culture confirmed typhoid fever in a provincial hospital in the Philippines.

Epidemiological features of blood culture confirmed typhoid fever and antibiotic sensitivity of isolated Salmonella typhi strains were investigated in Bohol Province in Central Philippines from where no earlier information of these was avialable. Typhoid fever is endemic elsewhere in the Philippines (eg Metropolitan Manila and surroundings) where also multidrug resistant S. typhi strains have been detected. A laboratory for surveillance of invasive bacterial infections was established in a tertiary care government hospital, in Bohol, Central Philippines, in 1994. Patients with suspected typhoid fever or other serious infection were managed and blood cultures from them were taken according to clinicians' judgment. Blood cultures were processed and the isolated bacteria identified using generally accepted methods. S. typhi and other Salmonella isolates were identified using commercial antisera. Patient data were collected from hospital records. Of a total of 4,699 blood cultures done during a period of 3 3/4 years, 1,530 (32%) were requested for suspected typhoid fever. S. typhi was the most common pathogen isolated from 422 patients (8.9%), followed by S. paratyphi A from 55 patients (1%). Most patients were young adults (43%) and school age children (28%). Male:female ratio was 1.5:1. Among the 422 patients, there were 9 (2%) deaths due to typhoid fever, all with complications. All S. typhi isolates were sensitive to chloramphenicol, cotrimoxazole, and ampicillin. Our observation on blood culture confirmed typhoid fever demonstrates its importance as a major infectious disease in Bohol and gives a sound basis for treatment of typhoid patients and for further clinical and epidemiologic studies of typhoid fever and for following antibiotic sensitivity of S. typhi in Bohol and elsewhere in the Philippines.

Antibody responses of three Haemophilus influenzae type b conjugate vaccines after one, two and three doses in Filipino children.

Differences in the magnitude of antibody response after one, two or three doses of Haemophilus influenzae type b conjugate vaccines have been reported which may influence decision-making regarding which vaccine should be used. This is of particular importance in developing countries where children may not receive a full immunization series and the vaccination schedule may be delayed. Serum antibody responses to three Hib capsular polysaccharide protein conjugate vaccines (PRP-OMP, HbOC and PRP-T) were evaluated in 102 Filipino infants. Vaccination was carried out at 6, 10 and 14 weeks of age based on the national Expanded Programme on Immunization (EPI) schedule together with diphtheria-tetanus-pertussis, hepatitis B and oral poliomyelitis vaccines. Sera were collected at 6 weeks and 1 month after each vaccination. Anti-Hib polysaccharide antibody concentrations were determined by Farrtype radioimmunoassay (RIA) and enzymeimmunoassay (EIA), Following the first dose, the geometric mean concentrations (GMC, micrograms ml-1) for PRP-OMP, HbOC and PRP-T were 0.69, 0.27 and 0.38, respectively. After two doses, there was a significant response (P < 0.05) to PRP-OMP and PRP-T (0.89 and 1.47) but not for HbOC (0.37). Differences in the GMC after the primary series were significant (pairwise P < 0.05): GMC was highest for PRP-T (4.0), followed by HbOC (1.6) and PRP-OMP (1.1). All three Hib vaccines were immunogenic when given in the local EPI schedule in Filipino infants although significant differences in the kinetics and magnitude of antibody responses were noted. The anti-Hib antibody concentrations determined by RIA and EIA were also compared in order to validate the latter for use in laboratories where it is feasible. There was a good correlation (r2 = 76%; P = 0.0001) in the Hib antibody titres obtained by both assays.

Evaluation of sampling sites for detection of upper respiratory tract carriage of Streptococcus pneumoniae and Haemophilus influenzae among healthy Filipino infants.

Two sampling techniques, nasal swabbing and oropharyngeal swabbing, for detection of the upper respiratory tract carriage of Streptococcus pneumoniae and Haemophilus influenzae were studied prospectively with 296 healthy Filipino infants at various ages: 6 to 8, 10 to 12, 14 to 17, 18 to 22, 32 to 39, and 46 to 65 weeks. In all age groups S. pneumoniae was isolated significantly more often (P < 0.0001) from the nasal site than from the oropharyngeal site. H. influenzae was found equally often at both sites.