Epidemiology of tetanus in the Marches Region of Italy, 1992-95.

Introduction In 1994, the countries of the Region of the Americas established the goal of eliminating measles from the Western Hemisphere by the year 2000 (1). Measles is one of the most highly infectious diseases, and in the prevaccine era, essentially everyone eventually acquired measles infection, usually as a very young child. Humans are the only reservoir for measles infection, although some other primates, such as monkeys, can be infected. The patient is most infectious during the prodromal phase of the disease before the onset of symptoms such as fever and rash. Communicability decreases rapidly after the appearance of rash (2). Live attenuated measles vaccine, first licensed for use in the USA in 1963, was in widespread use by the late 1970s (3). Immunization with this vaccine has been demonstrated to be protective for over 20 years, but immunity following vaccination is thought to be life-long (4). Vaccine efficacy has been shown to be 90-95%. Because of interference of maternal antibodies, vaccine efficacy increases steadily after 6 months of age, reaching its maximum plateau of 95-98% at 12-15 months of age. By 1982, virtually all countries in the world had incorporated measles vaccine into their routine vaccination schedules and, since then, coverage has increased substantially. By 1990, the estimated overall global coverage for children by 2 years of age was approximately 70%. Before the introduction of measles vaccine, epidemics characteristically tended to recur every 2-3 years in most densely populous areas, but with the widespread use of measles vaccine, the interval between outbreaks has lengthened (5, 6) and an increase in the average age of infection is observed. In the developing countries which recently introduced the vaccine and have not yet achieved high immunization coverage, measles remains endemic with most cases occurring in young children and infants (7). WHO has estimated that 40 million measles cases, with 1 million deaths, are still occurring annually in the world. PAHO measles eradication strategy The Pan American Health Organization (PAHO) recommends a strategy that aims to interrupt rapidly measles transmission by initially conducting a one-time-only mass campaign targeting all children aged 9 months to 14 years and to maintain interruption of transmission by sustaining high population immunity through vaccination of infants at routine health services facilities, supplemented by periodic mass campaigns conducted approximately every 4 years, targeting all 1-4-year-olds, regardless of previous vaccination status. "Fever and rash" surveillance and measles virus surveillance are other key elements of the strategy (8). The initial "catch-up" measles vaccination campaign is conducted during periods of low measles transmission. All children aged 9 months to 14 years, irrespective of vaccination history or reported history of measles infection, are immunized with measles vaccine within a very short period of time, usually one week to one month. These campaigns result in a rapid increase in population immunity and, if high enough coverage is achieved, measles transmission is interrupted. After a catch-up campaign has been conducted, there may still remain pockets of susceptible children. To detect these, a post-catch-up campaign evaluation is conducted and special vaccination (mop-up) activities are carried out in such areas to increase their level of coverage. After the initial catch-up campaign and mop-up operations, routine immunization services (keep-up) should ensure that all new birth cohorts of children are vaccinated with a dose of measles vaccine at 12-15 months of age. However, there will inevitably be an accumulation of susceptible preschool-aged children over time. Two major factors contribute to the accumulation of susceptibles. First, measles vaccine is not 100% effective, thus leaving some children unprotected despite vaccination. …