Pilar Muñoz

Effectiveness of measles vaccination for control of exposed children

The effectiveness of measles vaccine for postexposure prophylaxis at educational centers was investigated. A total of 166 children who shared the classroom with 10 confirmed cases during the infectious period of cases were studied. Of total susceptible exposed children, 72% (54/75) were vaccinated and 25 contracted measles. Vaccine effectiveness in children vaccinated within 72 hours of exposure was 90.5% (95% confidence interval, 34%–99%).

Monitoring mortality as an indicator of influenza in Catalonia, Spain.

STUDY OBJECTIVE: This study aimed to investigate the behaviour of two indicators of influenza activity in the area of Barcelona and to evaluate the usefulness of modelling them to improve the detection of influenza epidemics. DESIGN: Descriptive time series study using the number of deaths due to all causes registered by funeral services and reported cases of influenza-like illness. The study concentrated on five influenza seasons, from week 45 of 1988 to week 44 of 1993. The weekly number of deaths and cases of influenza-like illness registered were processed using identification of a time series ARIMA model. SETTING: Six large towns in the Barcelona province which have more than 60,000 inhabitants and funeral services in all of them. MAIN RESULTS: For mortality, the proposed model was an autoregressive one of order 2 (ARIMA (2,0,0)) and for morbidity it was one of order 3 (ARIMA (3,0,0)). Finally, the two time series were analysed together to facilitate the detection of possible implications between them. The joint study of the two series shows that the mortality series can be modelled separately from the reported morbidity series, but the morbidity series is influenced as much by the number of previous cases of influenza reported as by the previous mortality registered. CONCLUSIONS: The model based on general mortality is useful for detecting epidemic activity of influenza. However, because there is not an absolute gold standard that allows definition of the beginning of the epidemic, the final decision of when it is considered an epidemic and control measures recommended should be taken after evaluating all the indicators included in the influenza surveillance programme.

The impact of the introduction of the 14-3-3 protein assay in the surveillance of sporadic Creutzfeldt-Jakob disease in Catalonia

Abstract The 14-3-3 assay in the CSF has a high predictive value for the diagnosis of sporadic Creutzfeldt-Jakob disease (CJD). Our objective was to analyse the trends in mortality and incidence rates of CJD in Catalonia, an autonomous community of Spain, setting the cut off point the date when the 14-3-3 assay was incorporated to our CJD surveillance system. Only definite and probable cases according to the criteria adapted from Masters and colleagues were included for the analysis. Familial cases were excluded after genetic analysis of the PrP gen. We found a quasi three-fold increase in the incidence and mortality rates for CJD after introduction of the 14-3-3 assay in our surveillance system in 1997 as compared with the period 1993–1996. Our findings suggest an improvement of case ascertainment in part due to the introduction of the 14-3-3 assay in the surveillance system.

A GEE moving average analysis of the relationship between air pollution and mortality for asthma in Barcelona, Spain

Several studies have assessed the association between air pollution and hospital admissions or emergency room visits for asthma. Because of both the presence of missing data and the small number of observations, the relationship between air pollution and mortality for respiratory causes has been rarely analysed, and when it has, the results are very inconclusive or even inconsistent. The objective of this study is to assess the relation between levels of air pollutants (black smoke, sulphur dioxide, nitrogen dioxide and ozone), meteorological variables (24th average temperature and relative humidity) and daily mortality for asthma (ICD-9 493, 2 to 45 years old) in Barcelona, Spain, during the period 1986-1989. Since the range of daily mortality for asthma (2 to 45 years old) during the period 1986-1989 was 0-1), we have preferred to consider this variable as dichotomous. First, the relationship between air pollutants, meteorological variables and daily mortality (controlled for the occurrence of asthma epidemics) was estimated using logistic regression models. As was expected, the residuals from this regression were autocorrelated, showing a complex moving average (MA) structure. If covariates were not time dependent the so-called generalized linear mixed models, could be applied. In our case the covariates vary. As a consequence the likelihood is numerically intractable because it involves the evaluation of n-fold integral. An alternative method that avoids these numerical problems is the generalized estimating equations method (GEE). It is a multivariate analogue of quasi-likelihood estimation. In the absence of a likelihood function the parameters can be estimated by solving a multivariate analogue of the quasi score function. We have modified the GEE method in this paper, allowing for a different structure in the error covariance matrix (MA). Both air pollutants and meteorological variables are related with the occurrence of a death for asthma. In this sense, nitrogen dioxide, NO(2) (ss=0.037, p<0. 05), ozone, O(3) (ss=0.021, p<0.06) and high temperature (the sss were in the range (0.098-0.182), p<0.05) increased the probability of dying for asthma in Barcelona during the period 1986-1989.

Evaluación del impacto de los programas de vacunación masiva: la experiencia de la hepatitis A en Cataluña

Background: The hepatitis A + B vaccination programme of preadolescents was introduced in 1998 in Catalonia. During the following years, one of the main objectives has been to quantify the reduction in the incidence of hepatitis A caused by the vaccination programme. Methods: A retrospective analysis applying the space-time scan statistic to reported incidence rates of hepatitis A was carried out in the counties of Catalonia from 1992 to 2007. The relative risk (RR) was calculated and the spatial autocorrelation was estimated using Morans I statistic. Results: Six of the 7 space-time clusters identified by the scan statistic occurred in the pre-vaccine era (1992-1998) and only one in the post-vaccine era (1992-2007). In the first 10 four-weekly periods of the post-vaccine era (1999-2005) there was a significant reduction in the incidence of hepatitis A in Catalonia with respect to the pre-vaccine era (1992-1998) (p<0,01). Conclusions. Morans I statistic showed no pattern of global spatial dependence and was useful in detecting local clusters. These results corroborate previous studies that attributed most of the reduction in the incidence of hepatitis A in Catalonia to the effect of vaccination.

Capítulo 10 – Análisis de supervivencia

en la investigación clínica y epidemiológica. Gran número de artículos en las revistas más prestigiosas usan alguno de sus métodos. Aunque el origen del nombre se debe a la construcción de tablas de vida en el siglo XVII, sus aplicaciones se extienden al estudio del tiempo transcurrido entre dos eventos de interés, como podría ser la aparición de un acontecimiento adverso tras una intervención terapéutica o el tiempo transcurrido entre el inicio de una infección y su diagnóstico. En el proceso de obtención de pruebas empíricas en las que basar las decisiones clínicas, el análisis de supervivencia abordará las tres situaciones clásicas que resuelve la inferencia estadística: