Persistence of long-term immunity to hepatitis B among adolescents immunized at birth.

The long-term duration of recombinant hepatitis B vaccine-induced immunity among persons vaccinated starting at birth is still not well understood. Waning of vaccine-induced immunity could leave young adults at risk of hepatitis B virus infection due to behavioral or occupational exposures. We followed a cohort of children immunized starting at birth with a 3-dose regimen of recombinant hepatitis B vaccine (5 mcg, 2.5 mcg, 2.5 mcg). They were challenged with a booster dose of the hepatitis B vaccine 10 and 15 years after vaccination to assess anamnestic response as a measure of persistence of protection. Among 108 participants who had lost protective antibody levels against hepatitis B, the majority (>70%) had an anamnestic response to the booster dose; response rates did not decline significantly between 10 and 15 years follow-up periods. A high antibody concentration following primary vaccination was independently associated with an anamnestic response later on in life. Nonetheless, ~20-30% of participants were unable to mount an immune response after boosting. Hepatitis B revaccination might be required for persons vaccinated starting at birth if opportunities for hepatitis B virus exposure exist. Future vaccine recommendations should be based on studies ascertaining protection against clinically significant disease.

The epidemiology of leptospirosis in Palau.

BACKGROUND: Leptospirosis has been a longstanding problem in Palau, and Public Health programs were implemented in 2000 to conduct surveillance for cases of the disease. Epidemiologic analysis of leptospirosis cases is needed to describe disease occurrence in Palau and to help target prevention and control efforts. METHODS: Case data were collected from the Palau Ministry of Health's Reportable Disease Surveillance System. Descriptive epidemiology was performed on the case data, and spatial analysis was used to assess the distribution of leptospirosis cases in Palau. RESULTS: Between May of 2000 and June of 2006, 81 cases of leptospirosis occurred in Palau. Characteristics of the case population included being male (72.8%), being Palauan (70.4%), having an indoor occupation (71.0%), and living in an urban area of Palau (80.3%). It was also found that non-Palauan cases were significantly more likely to die of leptospirosis compared to the Palauan cases (p = 0.0018). Non-Palauan cases were significantly more likely to live in rural areas of Palau (p = 0.0001). There was no significant difference in the disease risk when comparing urban and rural areas. The crude disease risk for Palau is 401.9 (95% Cl 313.8-489.9) cases per 100,000 for the 6.2-year study period, and the average annual risk was 65.2 per 100,000. CONCLUSIONS: Leptospirosis continues to be present in Palau, and prevention and control measures should be continued and targeted toward specific states and hamlets of Koror. Furthermore, non-Palauan populations should be targeted for interventions to prevent more severe outcomes of this disease.

The epidemiology of dengue fever in Palau.

BACKGROUND: Dengue fever has been a longstanding problem in Palau, and Public Health programs were implemented in 2001 to conduct surveillance for cases of the disease. Epidemiologic analysis of dengue fever cases in Palau is needed to describe disease occurrence in Palau and to help target prevention and control efforts. METHODS: Case data were collected from the Palau Ministry of Health's Reportable Disease Surveillance System. Descriptive epidemiology was performed on the case data, and spatial analysis was used to assess the distribution of dengue fever cases in Palau. RESULTS: Between January of 2001 and June of 2006, 676 cases of dengue fever occurred in Palau, and sporadic outbreaks without seasonality were noted. Characteristics of the case population included being male (57.8%), being under the age of 20 (mean age = 23.4 years), being Palauan (88.2%), having an indoor occupation (91.7%), and having no history of travel outside of Palau during the estimated exposure period (96.3%). Most cases also lived in urban areas of Palau (92.0%), and the disease rate was significantly higher in urban areas compared to rural areas (3941.8 versus 1175.7 cases per 100,000, respectively for the 5.4-year study period; p = 0.0007). CONCLUSION: This study supports the idea that dengue fever is still endemic in Palau. Control and prevention measures should be continued, and targeted toward urban areas and populations at increased risk of this disease.