Serological tests (IgG) for dengue were performed at the Flavivirus Laboratory of the Oswaldo Cruz Institute (Rio de Janeiro) using PANBIO dengue selleck chemicals llc IgG indirect Elisa (Brisbane, Australia) [10]. Dengue is a flavivirus with widespread circulation in Brazil. Neutralising antibody response to
YF vaccine is highly specific with no or low-titre antibodies to other flavivirus, but evidence for interference by naturally acquired heterologous flavivirus immunity with 17D vaccine in humans is conflicting [11]. The response variable of interest was the serum neutralising antibody titres (in IU/mL), which were converted to log10 values and categorised. The co-variables of interest were age (in years), gender, presence of anti-dengue virus antibodies, prior vaccination, history of severe illness (hospitalisation, disease sequelae, and disability),
comorbidity and medications used at the Selleckchem AZD4547 time of blood collection. The rate of seropositivity and the geometric mean antibody titres, along with the corresponding 95% confidence intervals (CI), were estimated for each subgroup of time since vaccination. In the multivariate analysis, the immune response (indicated by log10 of titres in the multiple regression model and seropositivity in the logistic regression model) was modelled as a function of the time (in months) elapsed since vaccination as a continuous variable and categories: 30–45 days, 1–9 years, 10–11 years, and ≥12 years after primo-vaccination (categories 1–4 and 5–9 years were collapsed for multivariate analysis). The co-variables included in the model were age, gender, city of residence, and serological status for dengue. Statistical analysis was performed using the software SPSS® (SPSS Inc., Chicago, IL) and WINPEPI [12]. The study group consisted of a non-random sample of 721 adult volunteers, which included military personnel from 7 Army units located in the city of Rio de Janeiro (50.7%), and civilians from the Manguinhos campus at FIOCRUZ in Rio de Janeiro
(16%) and from health centres in Alfenas, Minas Gerais (33.3%). Volunteers were recruited between August 2011 and July 2012. The recruitment sites were selected based on expected numbers of eligible subjects. Of the 721 volunteers, 691 (95.8%) met all eligibility STK38 criteria and were included in the analysis (Fig. 1). The eligible volunteers were predominantly male (73.4%), aged 18–83 years, and the time since vaccination ranged from 30 days to 18 years. In the newly vaccinated subgroup all subjects were male, aged 18–30 years, and the time since vaccination ranged from 30 to 45 days (data not shown). Subjects aged 31–59 years had that highest proportion with 12 years or more of vaccination, whereas most volunteers 60 years and older had been vaccinated 5–9 years before (Table 1).