Evaluation of an innovative differential serology for hepatitis A serodiagnosis, and a seroprevalence study in children and adolescents, up to 11 years following the introduction of universal mass vaccination with a single dose in Bogotá, Colombia.
Hepatitis A is one of the most common food- and water borne diseases in low and middle-income countries; it can trigger severe outbreaks and lead to acute hepatic faliure in high-risk population subgroups. The universal mass vaccination in infants has been an invaluable strategy to advance towards disease control in settings with an intermediate burden of infection. Although most of the vaccination programmes targeting children recommend two doses, a growing number of countries have started schemes with one single-dose to save costs substantially and to reach, presumably, an effectiveness that may be comparable to two doses.
Colombia is a middle-income country where universal vaccination with a single dose for 12-months old infants has been proposed as a cost-effective vaccination strategy and implemented at a nationwide level, within the mandatory immunization schedule. Bogotá, its capital city, was pioneer in the introduction of such vaccination programme in 2008. At both nationwide and worldwide levels, there is a critical gap of knowledge regarding the long-term persistance of antibodies following the administration of one single dose. Serological differentiation between infected and vaccinated individuals is of paramount importance to examine both persistance of vaccine-induced antibodies over time, and the seroepidemiological transition gained following the start of universal vaccination.
We conduct a study that follows two methodological approaches and aims primarily to validate an innovative differential serology for discrimination between natural infection and vaccination in a local setting of Colombia, as well as to examine the hepatitis A serostatus of children and adolescents, 11 years after the introduction of the universal mass vaccination in Bogotá, Colombia. Such examination will in turn allow evaluating the seroepidemiological transition achieved after the start of the immunization programme.
A cross-sectional study in scholar children and adolescents is conducted in Bogotá, Colombia. Two concurrent cohorts are defined: children born after the start of the vaccination programme (aged between 6 and 12 years old), and adolescents born before (13 and 17 years old). We collect a blood sample from each study participant to analyze their serological status through both ELISA and an innovative, luminiscence-based, differential multiplex serology. We apply a questionnaire to explore hepatitis A risk factors and possible predictors of vaccine response. Validity and realiability of such serology will be analyzed, compared to vaccination cards and ELISA. Prevalence of immune, infected, vaccinated and susceptible individuals will be estimated in each cohort.
To the best of our knowledge, this is the first study, at a worldwide level, to implement a differential serology that has previously demonstrated high diagnostic performance to discriminate between infected and vaccinated individuals, and the first serosurvey in Colombia to assess long-term persistance of antibodies within its immunization programme with one-single dose. Our results will help to inform local public health policies aimed at hepatitis A control, and to guide decisions on the need to implement a second dose.
- National University of Colombia. (Universidad Nacional de Colombia). Bogotá, Colombia.
- Local Institute of Science, Biotechnology and Innovation in Health. (Instituto Distrital de Ciencia, Biotecnología en Innovación en Salud - IDCBIS - ). Bogotá, Colombia
- Local Health Office (Secretaría Distrital de Salud de Bogotá). Bogotá, Colombia
PhD Student involved
Johanna Torres MD. MSc. PhD Candidate Epidemiology