Hepatitis D virus and hepatitis B virus infection in Amerindian communities of the Amazonas state, Colombia.

BACKGROUND: In Colombia, cases of Hepatitis D virus (HDV) infection have been officially described since 1985 mainly in Amerindian population from Sierra Nevada de Santa Marta (North Caribbean Coast), Uraba (North West), and Amazon (South East). The last official report of a clinical case of HDV infection in Colombia was registered in 2005. OBJECTIVES: The aims of this study were to identify cases of HDV and/or Hepatitis B virus (HBV) infection in asymptomatic Amerindians from Amazonas state, South East Colombia, and to describe the circulating viral genotypes in this population. STUDY DESIGN: The study population was recruited in 19 Amerindian communities in the Amazonas state. Individuals over 18 years old were screened by rapid test for Hepatitis B surface Antigen (HBsAg). Blood samples obtained from individuals positives for HBsAg in the rapid-test assay were analyzed for HBsAg, anti-HBc, anti-HDV IgM/IgG by ELISA. The detection of HBV DNA and HDV RNA was performed by PCR amplification. The viral genotype was determined by sequencing and phylogenetic analysis. RESULTS: A total of 23/861 individuals were positive for HBsAg detection by rapid test. Serological and/or molecular markers of HDV infection were demonstrated in 43.5 % (10/23) of samples from Amerindians. The phylogenetic analysis demonstrated the exclusive circulation of HBV subgenotype F1b of and HDV 3 in this population. CONCLUSIONS: A high frequency of HBV/HDV infection was found in Amerindian population from Amazonas State, Colombia (43.5 %, 10/23). Nine cases were identified in a population of 861 asymptomatic Amerindian individuals; one symptomatic case (with diagnosis of end-stage hepatic disease) was also identified in the study. The circulation of HDV 3 and HBV subgenotype F1b suggests a constant flow of these viral genotypes as a result of the interaction of the Amerindian populations from Amazon basin. Further studies are necessary to confirm whether HBV subgenotype F1b is the prevalent in the population from South East region in Colombia.

Internal travel and risk of dengue transmission in Colombia.

Human behavior plays a key role in the dynamics of dengue transmission. However, research on the relationship between human movement and dengue transmission within endemic countries is limited. From January 2008 to December 2011, the authors of this study conducted a retrospective analysis of imported dengue infections in Bogotá, Colombia. Bogotá is a vector-transmission-free city that is also the capital district and most populated municipality in Colombia. The study revealed that 1) Bogotá inhabitants acquired dengue infection in diverse localities throughout the country but the largest proportion of cases (35.6%) were contracted at popular tourist destinations in dengue-endemic areas near Bogotá (<200-km radius from city limits), and 2) the number of imported dengue cases increased after major holidays, a transmission pattern not seen in dengue-endemic areas, where disease incidence correlates with rainy periods. It is therefore recommended that physicians consider the effect of travel when diagnosing their patients' illnesses, especially outside dengue-endemic areas where diagnosis of the disease can be challenging due to its nonspecific symptoms. The study also showed that analysis of dengue cases imported to regions free of vector transmission can generate an evidence-based model for characterizing the impact of human movement on the spread of diseases like dengue in countries where they are endemic.

[Impact assessment of the rotavirus vaccine in Colombia using rapid evaluation methods]. / Evaluación del impacto de la vacuna contra rotavirus en Colombia usando métodos rápidos de evaluación.

OBJECTIVE: Estimate the effectiveness of the monovalent rotavirus vaccine in preventing the need to hospitalize children under 2 years old for acute diarrheal disease in five Colombian cities. METHODS: A population survey was conducted based on a probability sample of children over 2 months and under 24 months of age in five Colombian cities (Barranquilla, Bogotá, Cali, Cartagena, and Riohacha) over the period from August through October 2010. The vaccine had been introduced in the Expanded Program on Immunization in January 2009. Rotavirus vaccination coverage was estimated by age group; the cumulative incidence of hospitalization for severe diarrhea was determined; and the magnitude of correlation between vaccination with one or two doses of rotavirus vaccine and hospitalization for diarrhea was calculated using the age-adjusted probability ratio (PR) and other epidemiologically significant factors. Effectiveness of the vaccine was estimated using the expression 1-PR. RESULTS: Coverage with a single dose of the rotavirus vaccine was 87.3%. During the 12 months prior to the survey, 1 453 of the children under 24 months old in the study areas (43.2%) had presented with diarrhea, and of these, 174 (5.2%) had been hospitalized for this cause. The effectiveness of two doses of the vaccine in preventing hospitalization for severe diarrhea was 68% (CI 95% = 55%-77%). CONCLUSIONS: In Colombia, rotavirus vaccination protects against hospitalization for diarrhea due to any cause. The use of cross-sectional surveys appeared to be adequate for rapid evaluation of an immunization program's effectiveness with a new vaccine.

Understanding how socioeconomic inequalities drive inequalities in COVID-19 infections.

Across the world, the COVID-19 pandemic has disproportionately affected economically disadvantaged groups. This differential impact has numerous possible explanations, each with significantly different policy implications. We examine, for the first time in a low- or middle-income country, which mechanisms best explain the disproportionate impact of the virus on the poor. Combining an epidemiological model with rich data from Bogotá, Colombia, we show that total infections and inequalities in infections are largely driven by inequalities in the ability to work remotely and in within-home secondary attack rates. Inequalities in isolation behavior are less important but non-negligible, while access to testing and contract-tracing plays practically no role because it is too slow to contain the virus. Interventions that mitigate transmission are often more effective when targeted on socioeconomically disadvantaged groups.

Risk factors for SARS-CoV-2 transmission in close contacts of adults at high risk of infection due to occupation: results from the contact tracing strategy of the CoVIDA epidemiological surveillance study in Bogotá, Colombia, in 2020-2021.

OBJECTIVES: To estimate the risk factors for SARS-CoV-2 transmission in close contacts of adults at high risk of infection due to occupation, participants of the CoVIDA study, in Bogotá D.C., Colombia. SETTING: The CoVIDA study was the largest COVID-19 intensified sentinel epidemiological surveillance study in Colombia thus far, performing over 60 000 RT-PCR tests for SARS-CoV-2 infection. The study implemented a contact tracing strategy (via telephone call) to support traditional surveillance actions performed by the local health authority. PARTICIPANTS: Close contacts of participants from the CoVIDA study. PRIMARY AND SECONDARY OUTCOME MEASURES: SARS-CoV-2 testing results were obtained (RT-PCR with CoVIDA or self-reported results). The secondary attack rate (SAR) was calculated using contacts and primary cases features. RESULTS: The CoVIDA study performed 1257 contact tracing procedures on primary cases. A total of 5551 close contacts were identified and 1050 secondary cases (21.1%) were found. The highest SAR was found in close contacts: (1) who were spouses (SAR=32.7%; 95% CI 29.1% to 36.4%), (2) of informally employed or unemployed primary cases (SAR=29.1%; 95% CI 25.5% to 32.8%), (3) of symptomatic primary cases (SAR of 25.9%; 95% CI 24.0% to 27.9%) and (4) living in households with more than three people (SAR=22.2%; 95% CI 20.7% to 23.8%). The spouses (OR 3.85; 95% CI 2.60 to 5.70), relatives (OR 1.89; 95% CI 1.33 to 2.70) and close contacts of a symptomatic primary case (OR 1.48; 95% CI 1.24 to 1.77) had an increased risk of being secondary cases compared with non-relatives and close contacts of an asymptomatic index case, respectively. CONCLUSIONS: Contact tracing strategies must focus on households with socioeconomic vulnerabilities to guarantee isolation and testing to stop the spread of the disease.

[Epidemiological and economic impact of tetanus vaccination in Colombian adults]. / Impacto epidemiológico y económico de la vacunación contra el tétanos en adultos de Colombia.

OBJECTIVE: Assess the potential epidemiological and economic impact of vaccinating the over-15 Colombian population against tetanus with a booster dose every 10 years. METHODS: A cost-effectiveness analysis of tetanus vaccination with a booster dose every 10 years was conducted in Colombia and compared with the current strategy (2, 4, 6, 18, and 60 months). Estimates of the burden of disease were based on three official data sources. A Markov model from the perspective of the third party payer was developed. The time horizon was the lifetime of a person. Deterministic and probabilistic sensitivity analyses were conducted. RESULTS: In Colombia, 30 to 48 cases of tetanus resulting in 9.6 to 10.1 deaths are reported each year. Although booster vaccination for the entire population was cost-effective (the cost per disability-adjusted life year [DALY] avoided was US$ 11,314 in the entire population), gender-based differentiation of the results showed that it would not be cost-effective in women (cost per DALY avoided was US$ 4,903 in men and US$ 22,332 in women). CONCLUSIONS: This is the first study that evaluates the cost-effectiveness of a tetanus vaccine booster dose every 10 years in a developing country. Use of this measure would be cost-effective in Colombia, especially for men. As a result of the gender-based differences in the results, any decision about its use in women of childbearing age should take current vaccination into account.

Incidence of acute respiratory symptoms and COVID-19 infection in children in public schools in Bogotá, Colombia, from July to November, 2020 / Incidence of acute respiratory symptoms and COVID-19 infection in children in public schools in Bogotá, Colombia, from July to November, 2020

INTRODUCTION: More than 90% of children infected with COVID-19 worldwide developed mild to moderate disease. In Colombia, during 2020, COVID-19 infections in children stayed below 9.2% of the total cases, with no trends for age group or sex. OBJECTIVE: To estimate the incidence of acute respiratory symptoms and COVID-19 in children from public schools in Bogotá, Colombia during the second semester of 2020. MATERIAL AND METHODS: A telephone survey was conducted in over 5,000 scholar children. Antecedents and use of health services were informed. Descriptive statistics were used. RESULTS: A total of 151.470 persons per day accounting for an IR of 157,8 per 100,000 people; almost three times the rate reported by the official surveillance system in the city. CONCLUSION: A lack of diagnosis and consultation in children was found compared to the general population. Further research is needed to elucidate the true burden of the disease in children.

Introducción. Más del 90% de los niños infectados con COVID-19 en el mundo, desarrollaron enfermedad leve a moderada. En Colombia, durante el 2020, la infección del COVID-19 en niños se mantuvo por debajo de 9,2 % del total de los casos sin tendencias por grupo de edad o sexo. Objetivo. Estimar la incidencia de síntomas respiratorios agudos y COVID19 en niños de escuelas públicas en Bogotá (Colombia) durante el segundo semestre de 2020. Materiales y métodos. Se hizo una encuesta telefónica en más de 5.000 escolares. Se recolectó información de antecedentes médicos y uso de servicios de salud. La información obtenida se describió mediante estadística descriptiva. Resultados. Se contabilizó un total de 151.470 personas al día para una tasa de incidencia de 157,8 en 100.000 personas, casi tres veces la tasa reportada por el sistema de vigilancia oficial de la ciudad. Conclusión. Se encontraron deficiencias en el diagnóstico y consulta de los niños, al compararlos con la población general. Se necesita más investigación para dilucidar la verdadera carga de la enfermedad en la población infantil.

COVID-19 spread, detection, and dynamics in Bogota, Colombia.

Latin America has been severely affected by the COVID-19 pandemic but estimations of rates of infections are very limited and lack the level of detail required to guide policy decisions. We implemented a COVID-19 sentinel surveillance study with 59,770 RT-PCR tests on mostly asymptomatic individuals and combine this data with administrative records on all detected cases to capture the spread and dynamics of the COVID-19 pandemic in Bogota from June 2020 to early March 2021. We describe various features of the pandemic that appear to be specific to a middle income countries. We find that, by March 2021, slightly more than half of the population in Bogota has been infected, despite only a small fraction of this population being detected. The initial buildup of immunity contributed to the containment of the pandemic in the first and second waves. We also show that the share of the population infected by March 2021 varies widely by occupation, socio-economic stratum, and location. This, in turn, has affected the dynamics of the spread with different groups being infected in the two waves.

[Economic impact of introducing the injectable inactivated polio vaccine in Colombia]. / Impacto económico de la introducción de la vacuna inactivada inyectable contra la poliomielitis en Colombia.

OBJECTIVE: Evaluate the cost-effectiveness of introducing the injectable inactivated polio vaccine (IPV) in Colombia versus the current system based on the use of the oral vaccine (OPV). METHODS: A Markov model was designed, based on a hypothetical cohort of newborns that would receive the IPV or the OPV vaccine, with a two-year follow-up and monthly estimates of the number of cases of vaccine-associated paralytic poliomyelitis (VAPP) that would emerge. The cost was analyzed from the perspective of the insurer (costs throughout life) and society (cases of VAPP and disability-adjusted life years [DALYs] prevented). RESULTS: From 1988 to 1998, some 22.5 million doses of OVP were administered in Colombia and nine cases of VAPP were detected, for a rate of 4.0 yen 10-7 dose. According to the model, 2 to 4 cases of VAPP could be anticipated in the following two years. The cost of treating the VAPP cases would total US$302,008, with the cost of vaccination with OPV coming to US$737,037 and with IPV, US$5,527,777. Vaccination with IPV would prevent 64 DALYs, at a cost of US$71,062 per DALY prevented; preventing one case of VAPP by substituting OPV with IPV would cost between US$1.8 and US$2.2 million. CONCLUSIONS: Substituting OPV with IPV is not a cost-effective measure in Colombia, even if the cellular vaccine against whooping cough currently in use were replaced with an acellular vaccine combined with an IPV.

Severe Acute Respiratory Syndrome Coronavirus 2 Seroprevalence Among Adults in a Tropical City of the Caribbean Area, Colombia: Are We Much Closer to Herd Immunity Than Developed Countries?

A serological survey was carried out in Monteria (500 000 population), a mid-size city in Colombia. An overall prevalence of 55.3% (95% confidence interval, 52.5%-57.8%) was found among a sample of 1.368 people randomly selected from the population. Test positivity was related to economic characteristics with the highest prevalence found in the most impoverished areas, representing 83.8% of the city's population. We found a prevalence that might be associated with some important level of population immunity.

Composition and biting activity of Anopheles (Diptera: Culicidae) in the Amazon region of Colombia.

To provide information for public health policy on mosquito nets in the Amazon region of Colombia, we conducted landing catches to estimate Anopheles species composition and biting activity. Two hundred twenty person-nights of catches were done in seven locations over a period of 14 mo. A total of 1,780 Anopheles mosquitoes were caught (8.1 per person-night). Among the nine species found, An. oswaldoi Peryassú was the most common (776 mosquitoes, 44%), followed by An. darlingi Root s.l. (498, 28%). An. oswaldoi was the most common species collected outdoors, where its biting rate dropped steadily from a peak of >15 bites/person-night at the start of the night (1800-1900 hours) to approximately equal to 2 bites/person-night before dawn. An. darlingi was the most common species collected indoors, with a biting rate of approximately equal to 3-4 bites/person-night until about midnight, when the rate dropped below 1 bite/person-night, before showing a secondary peak before dawn. Sixty-four mosquito nets were analyzed by the technique of high-performance liquid chromatography (HPLC) for levels of deltamethrin (DM). All but two (62) of these were reported by their owners to have been impregnated with insecticide, and 53 were found by HPLC to have deltamethrin. However, one half (32) of the nets had concentrations <4 mg/m2 and therefore were likely to have been inadequately protective. An inverse association was found between the reported time between washes and deltamethrin concentration. These findings show a need for additional protection from mosquitoes when not inside nets, as well as for more effective impregnation, possibly through wash-resistant insecticide formulation.

[Flu vaccine effectiveness: a metaanalysis]. / Efectividad de la vacuna contra influenza: metanálisis de literatura.

INTRODUCTION: Seasonal influenza is a disease of great interest in public health due to its high rates of infection and big costs, especially in high-risk population. This situation has motivated studies related to development of control measures necessary to mitigate its impact. Immunization constitutes a key role in providing the necessary interventions; however, little information is available about its effectiveness as public health measure in tropical countries. OBJECTIVE: The vaccine effectiveness was evaluated by means of published results in the scientific literature. MATERIALS AND METHODS: Meta-analysis techniques were used to summarize the results of epidemiological analytical studies. A critical evaluation was undertaken for each study to identify the potential biases and methodological limitations. RESULTS: Two hundred and fifty-seven relevant studies were located, of which 28 were included in the analysis. The pooled estimator of the vaccine effectiveness for hospitalization was 0.74 [95% CI 0.68-0.81] in older adults (65 years and older) in cases-control studies. For cohort studies, the obtained estimator was 0.80 [95% CI 0.68-0.91]. CONCLUSION: Other conclusions were analyzed, and in general, a protective effect was demonstrated in the vaccine. About 1,200,000 were involved, 530,000 of them were vaccinated. Geographically, the analyzed studies came from developed countries in Europe, America and Asia.

[Seroprevalence of hepatitis B virus and human immunodeficiency virus infection in a population of multiply-transfused patients in Colombia]. / Seroprevalencia de infección por virus de la hepatitis B y por virus de la inmunodeficiencia humana en una población de pacientes con múltiples transfusiones en cuatro hospitales, Colombia, Sur América.

INTRODUCTION: Although the transfusion of blood products is a common therapy, it carries risk of transmission of infections, especially hepatitus B virus (HBV) and human immunodeficiency virus (HIV). OBJECTIVE: As part of the blood safety initiative, the Pan American Health Organization supported studies to estimate the prevalence of human immunodeficiency virus and hepatitis B virus infection in Colombia. MATERIALS AND METHODS: Between February and September 2003, a cross sectional study examined 500 multiply-transfused patients at four hospital centers in the cities of Bogota and Medellin. The serum samples were analyzed by enzyme immunoassay (EIA) using commercial kits. RESULTS: The seroprevalence of HIV infection was 1.8% (CI 95% 0.5-3.1). The seroprevalence of HBV infection was 18.6% (CI 95% 15.1-22.1). Six risk factors were associated with HIV and HBV infection: (1) receiving more than 48 units of blood or blood components, (2) diagnosis of hemophilia, (3) receiving transfusions for more than one year, (4) receiving whole blood, (5) coinfection with hepatitis C virus and (6) receiving transfusions before 1993. CONCLUSIONS: This is the first epidemiological study with a significant sample size performed in multiply-transfused patients in Colombia. The principal finding was the high prevalence of HBV and HIV infection in patients with diagnosis of hemophilia compared with the other five groups of multiply-transfused patients.

Treatment of laser in situ keratomileusis interface epithelial ingrowth with neodymium:yytrium-aluminum-garnet laser.

PURPOSE: To evaluate the results obtained with the treatment for interface epithelial ingrowth after laser in situ keratomileusis (LASIK) with neodymium:yytrium-aluminum-garnet (Nd:YAG) laser. DESIGN: Retrospective, interventional, noncomparative, consecutive case series. METHODS: Thirty eyes were treated with Nd:YAG laser for clinically significant epithelial ingrowth developed after LASIK. Each impact produced an explosion with evaporation of epithelial cells giving rise to bubbles. The mean intensity of the spots was 0.6 mJ, and they were variable in quantity depending on the size of the epithelial ingrowth area. The patients were followed up for two years. RESULTS: The opacities caused by the epithelial ingrowth disappeared in 80% of the cases with the Nd:YAG laser treatment. In 40% of the cases, two or more sessions of Nd:YAG laser treatment were necessary to eliminate the epithelial ingrowth areas entirely. In 60% of the cases, visual acuity improved by one or more lines of vision and the corneal topography was more regular. After the treatment, symptoms like glare and halos improved in all cases. The intensity of the laser was adjusted in each case and was focused perfectly on the epithelial ingrowth areas. There were no complications. CONCLUSIONS: Nd:YAG laser, in our experience, is an easy and effective technique for the treatment of epithelial ingrowth after LASIK.

Severe respiratory disease and its relationship with respiratory viruses in Colombia.

BACKGROUND: There are important gaps in our understanding of the epidemiology of respiratory virus infections in tropical countries. In September 2003, the Colombian epidemiological surveillance system was notified of several deaths from an acute respiratory disease (ARD). METHODS: In order to identify the agents associated with ARD cases, a clinical and laboratory-based surveillance system was implemented throughout the country. RESULTS: Between September 19 and December 31, 2003, 64 suspected cases of ARD were reported; of these reported cases, 21 (33%) died. Among 25 patients who underwent virus studies, influenza A (H3N2) (n=7) was the most frequently identified agent. Other viruses included parainfluenza (4), influenza B (1), and respiratory syncytial virus (3). The peak occurrence of cases and deaths coincided with the replacement of the influenza A (H3N2) Panama strain, which had been circulating in Colombia since 1999, by three new influenza A (H3N2) strains (Korea, Fujian, and Wyoming). CONCLUSIONS: This outbreak led to the strengthening of surveillance for respiratory viruses and to new national recommendations for influenza vaccination in Colombia.

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.

[Molecular epidemiology of tuberculosis in Bogotá in clinical isolates obtained over an 11-year period]. / Epidemiología Molecular de la Tuberculosis en Bogotá en Aislados Clínicos obtenidos durante 11 Años.

OBJECTIVE: Characterising clinical Mycobacterium tuberculosis isolates obtained from 1995 to 2006 in Bogotá , Colombia , using standardised IS6110-based RFLP typing for determining phylogenetic relationships. Calculating cases due to recent infection (grouped cases) cf endogenous reactivation (single patterns). METHODS: This retrospective study characterised 137 clinical Mycobacterium tuberculosis isolates obtained in Bogotá from 1995 to 2006. Study variables consisted of gender, age, HIV status, homelessness, Ziehl Neelsen smear result and date of culture. All isolates were freshly identified by phenotypic methods, confirmed by PRA and evaluated for susceptibility to antimicrobial agents according to the proportional method. Mycobacterium tuberculosis cultures were typed by standardised IS6110-based RFLP. RESULTS: All isolates were confirmed as being M. tuberculosis by phenotypic and genotypic methods. 9,4 % monoresistance and 2,9 % MDR (rifampicin- and isoniazid-resistant) were found. 129 M . tuberculosis isolates were genotyped; 96 (74 %) of them presented unique DNA fingerprints, whilst 35 (26 %) were grouped into 17 clusters consisting of two to four isolates. Direct epidemiological links between patients could not be established in most cases. Only HIV status was a significant predictor of clustering amongst the variables being studied (p<0.05). CONCLUSION: The results of our study revealed a high proportion of unique DNA fingerprints, suggesting high genetic variability between M. tuberculosis strains in Bogotá , Colombia , meaning that most cases of TB in this study were attributed to endogenous reactivation.

Exploring scenarios of chikungunya mitigation with a data-driven agent-based model of the 2014-2016 outbreak in Colombia.

New epidemics of infectious diseases can emerge any time, as illustrated by the emergence of chikungunya virus (CHIKV) and Zika virus (ZIKV) in Latin America. During new epidemics, public health officials face difficult decisions regarding spatial targeting of interventions to optimally allocate limited resources. We used a large-scale, data-driven, agent-based simulation model (ABM) to explore CHIKV mitigation strategies, including strategies based on previous DENV outbreaks. Our model represents CHIKV transmission in a realistic population of Colombia with 45 million individuals in 10.6 million households, schools, and workplaces. Our model uses high-resolution probability maps for the occurrence of the Ae. aegypti mosquito vector to estimate mosquito density in Colombia. We found that vector control in all 521 municipalities with mosquito populations led to 402,940 fewer clinical cases of CHIKV compared to a baseline scenario without intervention. We also explored using data about previous dengue virus (DENV) epidemics to inform CHIKV mitigation strategies. Compared to the baseline scenario, 314,437 fewer cases occurred when we simulated vector control only in 301 municipalities that had previously reported DENV, illustrating the value of available data from previous outbreaks. When varying the implementation parameters for vector control, we found that faster implementation and scale-up of vector control led to the greatest proportionate reduction in cases. Using available data for epidemic simulations can strengthen decision making against new epidemic threats.

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.