Eight years of hepatitis B vaccination in Colombia with a recombinant vaccine: factors influencing hepatitis B virus infection and effectiveness.

OBJECTIVE: To evaluate the effectiveness of a recombinant hepatitis B vaccine used in endemic areas of Colombia, as well as risk factors associated with hepatitis B virus (HBV) infection and carriage after vaccine introduction. METHODS: A cross-sectional study was carried out in urban and rural areas of the Colombian Amazon, a highly endemic area for hepatitis B infection. Children under 12 years of age and their mothers were selected for the study using one-stage cluster sampling (N=2145) and were examined for HBV serological markers and antibodies against surface antigen (anti-HBs). RESULTS: There has been a reduction of 60-75% in the prevalence of HBV infection and hepatitis B surface antigen (HBsAg) carriage since HBV vaccination was introduced. Receiving the first dose of HBV vaccine at more than two months after birth was one of the factors associated with HBV carrier status. Maternal HBV infection was also associated with infection in the child. CONCLUSIONS: The recombinant Cuban hepatitis B vaccine has contributed to the reduction of the infection in this highly endemic area, though further efforts are required to improve timely vaccination for children at high risk.

Hepatitis B infection control in Colombian Amazon after 15 years of hepatitis B vaccination. Effectiveness of birth dose and current prevalence.

BACKGROUND: Hepatitis B virus (HBV) infection is highly endemic in the Colombian Amazon basin. In Colombia, the universal hepatitis B vaccination in that area has been active since 1993. The program targets children aged under five years. Newborns receive at least three doses, and in 2001, HBV vaccine birth dose was included. This study aimed to evaluate the advances on HBV control in the Colombian Amazon. METHODS: A population-based cross-sectional study was conducted in children less than 11 years old in rural areas of the Colombian Amazon, in order to assess the current levels of HBV prevalence and evaluate the effectiveness of HBV vaccination. Participants were selected from villages scattered along the Amazon, Putumayo and Loretoyaco Rivers. Blood samples were taken from children. All the samples were examined for surface antigen (HBsAg) and IgG antibodies against core antigen (AntiHBc) of HBV. Data on HBV vaccination status and other risk factors were also collected. RESULTS: Blood samples from 1275 children were included in the study. The positivity for IgG AntiHBC and HBsAg was 3.8% and 0.5%, respectively. It was observed that receiving a dose of HBV vaccine within 48 h after birth decreased the risk of HBV infection and carriage by 95%. Being born to an AntiHBc positive mother increased 8 times the risk of HBV infection (OR = 7.8 CI 95% 3.3-10.2) and 7 times the risk of HBsAg carriage (OR = 6.6 CI 95% 2.1-10.1). CONCLUSION: The prevalence of HBV infection and HBsAg carriage continues to decrease among children living in the Colombian Amazon. The high protective effectiveness of an HBV birth does suggest that perinatal transmission is important in endemic areas of Latin America, an aspect that has not been fully studied in the region.

Hepatitis C virus seroprevalence in multi-transfused patients in Colombia.

BACKGROUND: Hepatitis C Virus (HCV) infection is a public health problem worldwide, with particular relevance in multi-transfused patients given that HCV is principally transmitted by exposure to infected blood. STUDY DESIGN: Between February and September 2003 a cross-sectional study was carried out in four hospital centres in Bogotá and Medellin, Colombia, to determine the risk factors for HCV infection in 500 multi-transfused patients. RESULTS: The study population was distributed in five groups: haemophilia, haemodyalsis, acute bleeding, ontological illnesses and sickle cell disease or thalassemia. Serum samples from patients were tested for HCV antibodies (Asxym, Abbott). An overall prevalence (9.0%; 95% confidence interval (CI): 6.4-11.6) (45/500) of HCV infection was found. Anti-HCV antibodies were detected in 32.2% of patients with haemophilia, 6.1% of patients undergoing haemodialysis, 7.1% of patients with sickle cell disease or thalassemia, 2.6% of patients with acute bleeding and 3.4% of patients with ontological or hematological diseases. The main risk factors associated with infection by HCV were: to be hemophilic (odds ratio, OR = 18.03; 95% Cl: 3.96-114.17), having received transfusions before 1995 (OR = 12.27; 95% Cl: 5.57-27.69), and having received more than 48 units of blood components (OR = 6.08; 95% CI: 3.06-12.1). In the multivariate analysis, only the year of transfusions (before 1995) remained significantly associated with risk of infection by HCV. CONCLUSIONS: The data show a 3-fold reduction in the infection risk between 1993 and 1995, when the serological screening for HCV in blood donors was being introduced. A reduction greater than 90% was achieved by 1995 when the screening coverage reached 99%.

Vaccine coverage with hepatitis B and other vaccines in the Colombian Amazon: do health worker knowledge and perception influence coverage?

OBJECTIVES: We conducted a vaccination coverage survey in the Colombian Amazon, an area highly endemic for hepatitis B (HB), where HB vaccine was introduced in 1992. The aim was to measure vaccine coverage and factors influencing it, especially those related to health services. METHODS: A total of 3573 children younger than 11 years were randomly selected from four populations. Vaccination status was ascertained through the vaccination card and a questionnaire on socio-demographic factors was applied to children's caretakers. Health workers (HW) in charge of vaccination in rural and urban areas were interviewed regarding knowledge and practices in vaccination. Individual and HW characteristics were related to individual vaccination using logistic regression. RESULTS: Overall cumulated vaccination coverage was high for polio (96%, 95% CI: 94-98), measles (94%, 95% CI: 92.8-95.2), BCG (91%, 95% CI: 90-93), DPT (90%, 95% CI: 88-92) and HB (88%, 95% CI: 86-90). However, <50% of children completed the primary course of vaccination in the first year of life. Individual factors improving the likelihood of being either fully or HB vaccinated were: age>1 year, living in Leticia, being affiliated to the social security, and living in a house with a roof made of tiles rather than palm tree leaf. Among the variables related to HWs, poor knowledge of vaccine contraindications predicted a lower chance of being fully or HB vaccinated in the population served by them, even after controlling for individual variables. CONCLUSIONS: The HB control program in Colombia has achieved good coverage in one of the most endemic areas of the country. However, barriers to vaccination arise from inequities in the distribution of health insurance and inadequate HW knowledge.