Pulse mass measles vaccination across age cohorts.

Abstract

Although vaccines against measles have been routinely applied over a quarter of a century, measles is still persistent in Israel, with major epidemics roughly every 5 years. Recent serological analyses have shown that only 85% of Israelis aged 18 years have anti-measles IgG antibodies. Considering the high transmissibility of the virus and the hih level of herd immunity required for disease eradication, the Israeli vaccination policy against measles is now being reevaluated.Motivated by theoretical studies of populations in perturbed environments, we examined the possibility of replacing the conventional cohort vaccination strategy by a pulse strategyi.e., periodic vaccination of several age cohorts at the same time. Numerical studies of a deterministic age-structured model suggest that vaccination, which renders immunity to no more than 85% of the susceptible children aged 1-7 years, once every 5 years will suffice to prevent epidemics in Israel, where infection rate is highest amongst schoolchildren. The model suggests that by using such a strategy the density of susceptible individuals is always kept below the threshold above which recurrent epidemics will be maintained. Analysis of simpler, non-age-structured, models serves to clarify the basic properties of the proposed strategy. Our theoretical results indicate that the advantages and disadvantages of a pulse strategy should be seriously examined in Israel and in countries with simlar patterns of measles virus transmission.

Failure of vaccination to prevent outbreaks of foot-and-mouth disease

“…The data are used to provide parameter estimates for a mathematical model of the impact of vaccination programmes at the population level [7,8]. The model is based on standard epidemiological theory [1] but includes a more detailed representation of antibody responses to vaccination and the decay of these responses through time.…”

Predicting the impact of measles vaccination in England and Wales: model validation and analysis of policy options

“…Specifically, primary school-children (aged 5-11 years) are offered vaccine once every 5 years. The rationale behind this pulse vaccination policy has been the subject of a recent study [32] and in principle rests upon the idea of preventing the build-up of susceptibles in the high contact rate age classes (school ages) so important in driving epidemic cycles, and regularly suppressing susceptible numbers below epidemic proportions. Again a 50 % success rate is assumed, and the policy may be either selective or unselective.…”

A note on semi-discrete modelling in the life sciences

“…The most important application is the comparison between classical (continuous) vaccination and pulsed vaccination in epidemiological models (Agur et al 1993). Some other applications deal with the effect of seasonal demographic processes (birth and death).…”

“…A schematic representation of the dynamics followed by a semi-discrete dynamical system is illustrated in figure 1. Although most mathematically oriented contributions in semi-discrete (or pulsed, impulsive) systems share the same classical common mathematical formalism (see Agur et al 1993;Funasaki & Kot 1993;Panetta 1996), some others differ (e.g. Shaw 1994;Ghosh & Pugliese 2004;Singh & Nisbet 2007).…”

“…In a seminal paper, Agur et al (1993) proposed the idea of a 'pulse vaccination strategy' to improve the control of measles epidemics. Instead of a constant vaccination effort spread throughout the year, they proposed to vaccinate a proportion of the population within a very short period of time; vaccination was then a discrete process, while epidemic evolution was assumed continuous.…”