Seroprevalence of hepatitis B and factors potentially associated in a population-based study in Medellin, Colombia.

The seroprevalence of hepatitis B (HB) and of potentially associated factors in Medellin, Colombia, were investigated 17years after the start of universal vaccination. Biological and sociodemographic data from a population survey with a multistage random sampling were analyzed in 6-64year old individuals. HB surface antigen, total HB core antibodies and HB surface antibodies, and in some cases IgM antibodies to HB core antigen, were tested in 2077 samples. Factors potentially associated with and natural, and vaccine immunity relative to susceptibility (absence of any marker) were analyzed using a multinomial logistic regression. The prevalence of serological patterns was: chronic infection 0.20% (95% CI 0.11-0.71), vaccine immunity 25.10% (95% CI 21.72-28.83) and natural immunity 2.60% (95% CI 1.80-3.74). No markers were detected in 71.30% (95% CI 67.70-74.83) of the individuals and evidence of recent infection was not detected. Relative to the absence of markers, natural immunity was potentially associated with age (6-17years and 41-64years) and sleeping less than 6 hours, while vaccine immunity was associated with age (6-17years), reporting vaccination against HB, belonging to high socioeconomic strata, home ownership and being obese, after adjusting for other variables. These results may be a population effect of mass vaccination. It is recommended to complete the vaccination schedule and to study in detail, persistence of antibodies and the role of obesity and socioeconomic strata in the vaccine immunity.

Seroprevalence of mumps in an epidemic period in Medellín, Colombia.

OBJECTIVE: We related seroprevalence and outbreaks data in order to identify factors that could explain the occurrence of outbreaks despite high vaccination coverage in Medellín Colombia. METHODS: Samples from a population seroprevalence data obtained in 2009 in a random survey were analyzed. IgG levels were determined for mumps using 2 commercial tests of 2119 individuals aged 6-64 years. A comparative analysis was undertaken using age-specific mumps seroprevalence data and information of 98 epidemiological investigations of mumps outbreaks reported in 2009. RESULTS: Overall, seroprevalence was 91.6% (95% CI=89.3-93.5%). The age-specific seronegativity was 20.3% and 20.6% in age groups 11-15 years and 16-20 years respectively. Individuals aged 6-20 years were the most affected during outbreaks. In individuals born in 2003, a year after the change in the booster schedule from 10 to 5 years, the proportion of unvaccinated individuals (14%) and those who received only one dose of MMR (45%) increased substantially. On average, 23.5 days elapsed between the onset of symptoms in secondary cases and the outbreak investigation. CONCLUSION: Potential contributing factors for the occurrence of outbreaks of mumps were the relatively high prevalence of seronegativity among individuals aged 11-20 years, delays in investigation and control of outbreaks, and incomplete vaccination schedules.