[Update on chickenpox]. / Actualización en varicela.

Primary infection by varicella-zoster virus causes chickenpox and herpes zoster. At 14 years of age, 91% of the population have already suffered the illness and after 30 years, more than 95% have done so. In 1999, the hospitalization rate was 2.4 per 1,000 chickenpox cases in those under 14 and 15.5 per 1,000 cases in those over 14. A total of 73% of deaths recorded during the period 1991-2000 were in the older than 14 year old group. Efficacy of varicella vaccine after a 7-8 years period is 87%; a milder case of chickenpox (breakthrough) can appear in vaccinated people 42 days after vaccination. The introduction of the vaccine may be proposed to stop or decrease virus circulation among the population or to decrease complications and mortality from chickenpox. According to the objective proposed, different strategies that imply risks and benefits should be conducted.

[The effect of anti-measles control measures in health care within autonomous community of Madrid]. / Impacto de las medidas de control del sarampión por áreas sanitarias en la comunidad autónoma de Madrid.

BACKGROUND: Measles is a disease subject to a child vaceination programme that has undergone changes with respect to the epidemiological model employed. The purpose of this study is to define the temporal series of measles cases within the Autonomous Community of Madrid as of 1971 in each particular Medical Care Area, identify the risk of contracting the disease in each such area and to evaluate the effect of control measures against outbreaks of the disease. METHOD: A descriptive analysis is carried out of the temporal series relating to measles. Series components are obtained by means of a multiplication model: seasonal, cyclic or irregular trend. The break in transmission of the disease and risk attributed to each area is then compared. RESULTS: The number of reported cases of the disease decreased by 89% after implementation of the vaccination programme: the series has remained stable and it was observed that non-epidemie intervals have increased. The risk of contracting measles is greater in four Medical Care Areas and the transmission cycle has been broken in 6 Areas. CONCLUSIONS: Epidemiological behaviour of measles within the Autonomous Community of Madrid does not differ from other countries before and after the implementation of vaccination programmes. Evidence of the effects of control measures are evidenced by the decrease in the number of reported cases of the disease, change in the epidemiological pattern and break in transmission detected mainly in the Areas in which such controls have been carried out.

[Measures of the effect of vaccination in an outbreak of measles]. / Medidas del efecto de la vacunación en un brote de sarampión.

Vaccine efficacy, the effectiveness of a vaccination programme and the fraction of a population that would be necessary to vaccinate in order to prevent a measles outbreak are studied in a population having a vaccination programme. A dynamic model for acute, directly transmitted diseases was applied, based on the rate of transmission, namely, the probability that the infectious agent is transmitted from an infected to a susceptible person within a short space of time. We carried out a population-based study where we observed the final attack rates among vaccinated and unvaccinated people for a measles outbreak. In this population, the vaccination programme is responsible for a reduction of: 82.41% of all cases in the non-vaccinated sector; 98.45% of the average risk of disease among the vaccinated; and 97.29% of all cases among the population as a whole. Under these conditions there is the possibility of disease outbreaks arising, outbreaks which could be prevented if the percentage of the vaccinated population exceeded 95%.