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Article in Japanese

Epidemiological and virological investigation of measles in Sapporo during 2007-2008

Mayuko MORII1), Yuki KUROIWA1), Toshihiko MORI1), Koichi YANO2), Hiroyuki TSUTSUMI3)

We experienced a measles outbreak in Sapporo from August 2007 through July 2008. The Sapporo City Health Service recorded a total of 758 measles cases during this period. The outbreak was first observed among children in nursery school and kindergarten in the 2007 season. The epidemic continued and expanded to high school and university students during the 2008 season. The largest number of illnesses was observed among children less than 6 years old, accounting for 46% of all cases in 2007. However, it was most common among children more than 15 years old (60%) in 2008. We speculate that the epidemiological difference between 2007 and 2008 was caused by the low rate of vaccination and age-dependent decline of antibody titer. Most cases more than 15 years old had received only a single dose of vaccination, and some were unvaccinated. Almost a quarter of the patients in both 2007 and 2008 had already been vaccinated before the outbreak. Since the MR vaccine now in use is live attenuated, it is considered that low antibody production ability causes secondary vaccine failure (SVF). The effectiveness of defending infections by vaccination is expected to expire about 6 to 12 years later. Therefore multiple doses of measles vaccination for boosters are recommended to eliminate of an unexpected outbreak.

1) Departmeant of Pediatrics, NTT Higashinihon Hospital
2) Sapporo City of Institute of Public Health
3) Department of Pediatrics, School of Medicine, Sapporo Medical University

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Received January 28, 2010
Accepted September 21, 2010

23 (1):10─16,2011