Effectiveness assessment of vaccination policy against measles epidemic in Japan using an age–time two-dimensional mathematical model

Department of Human Ecology, Graduate School of Environmental Science, Okayama University, Okayama, 700-8530, Japan.
Environmental Health and Preventive Medicine 05/2011; 17(1):34-43. DOI: 10.1007/s12199-011-0217-y
Source: PubMed


In 2007, measles prevailed among the youth and young adult population in Japan, creating in a serious social problem. Among the developed countries, Japan has a relatively high incidence of measles. The objective of this study was to assess the effect of improvements in the vaccination policy against measles through simulations.
We developed an age-time two-dimensional model for the transmission of measles to reflect an age structure, enabling contact rate to be selected by age. Introduction of the maternal immunity class into the model allowed natural infection and vaccination to be discriminated along the course of an infant's mother acquiring the immunity, thereby resulting in an improved accuracy of the simulations in infants. Several vaccination scenarios were attempted in order to assess the influence of various vaccination policies on the prevention of a measles epidemic.
The results of this quantitative study indicated that suppression of a measles outbreak requires the maintenance of high vaccine coverage and that a decline in vaccine coverage may result in a measles epidemic.
The present standard immunization program for measles will maintain an acceptable level of immunity and is therefore associated with a low risk of an epidemic after discontinuation of the third and fourth stages as scheduled--as long as at least 90% vaccine coverage of the first and second is maintained. The simulation results show that discontinuation of the third and fourth stages of vaccination as scheduled should be accompanied by endeavors to maintain appropriate high vaccine coverage of the first and second stages.

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    ABSTRACT: Aim: Measles during pregnancy has deleterious effects on both perinatal and maternal outcomes. In Japan, local epidemics of measles and cases of measles during pregnancy are still being reported; therefore, the seroprevalence of antibodies to measles is suspected to be still not sufficient. The aim of this study was to analyze the seroprevalence of antibodies to measles in Japanese pregnant women and estimate the percentage of these women who require vaccination or revaccination against measles. Material and methods: We analyzed the seroprevalence of immunity to measles by the neutralization test in 10 349 pregnant women in the first trimester managed at the National Center for Child Health and Development between February 2004 and December 2010. The neutralization test titers were interpreted as follows: ≧1:8, seropositive; =4, low-positive; ≦4, seronegative. Results: Of the total number of pregnant women tested, 7408 (71.6%) were seropositive, 1864 (18.0%) were low-positive, and 1079 (10.4%) were seronegative for measles antibodies, respectively. Conclusion: Our results revealed that 28% of our pregnant population was seronegative or low-positive for measles antibodies, and thought to require revaccination or vaccination. Screening for measles immunity might be advisable for women of childbearing age.
    Journal of Obstetrics and Gynaecology Research 08/2012; 39(2). DOI:10.1111/j.1447-0756.2012.01997.x · 0.93 Impact Factor

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