The National Epidemiological Surveillance of infectious Diseases (NESID): Weekly cases of measles and rubella reported by pediatric sentinel clinics (about 2,500-3,000 clinics nationwide) after 1994 and those of adult measles reported by sentinel hospitals (about 500 hospitals nationwide) after April 1999 are shown in Fig. 1. Measles cases counted 11.20 per sentinel in 2001 (cumulative cases counted at 33,812 and estimated cases nationwide 286,000), the highest count since 1993, whereas they decreased largely to 2.72 (8,285 and 55,000) in 2003, 0.51 (1,547 and 12,000) in 2004, and 0.18 (545 and 4,200) in 2005. Cases of adult measles also decreased in parallel with this decrease; 0.98 per sentinel (cumulative cases being 462) in 2003, 0.12 (59) in 2004, and 0.02 (8) in 2005. In 1995, routine immunization of rubella to boys and girls was started and rubella cases largely decreased after 1999 (see IASR 24: 53-54, 2003), reaching 0.92 (cumulative cases 2,795 and nationwide estimated cases 22,000) in 2003, however in 2004, increased to 1.40 (4,239 and 39,000) and decreased again to the fewest, 0.29 (895 and 7,600) in 2005.
Cases by prefecture (Fig. 2) were counted over 2.00 per sentinel in 16 prefectures for measles and in 5 prefectures for adult measles in 2003 and 2 and 0 prefectures for measles in 2004 and 2005, respectively. In 2005, cases per sentinel were counted less than 0.5 for both measles and adult measles in all prefectures. For rubella, cases were counted over 2.00 per sentinel in 7 prefectures in 2004, while 0 prefectures in 2005, and less than 1.00 in all prefectures except one.
The ages of measles cases reported by pediatric sentinel clinics in 2005 were mostly one year as usual (Table 1), and the ratio of cases aged 1-5 years relatively increased as compared with those in 2003 and 2004. No case of adult measles in those younger than 24 years was reported (6 cases of 25-44 years and 2 of over 65 years). The ratio of 1-3 years among rubella cases reported by pediatric sentinel clinics in 2005 increased relatively and that of 10-14 years decreased.
Cases of CRS, one of the category V notifiable diseases, occurred one in each year during 2000-2003, 10 in 2004, and 2 in 2005, totaling 16 cases (5 males and 11 females). It is noteworthy that CRS cases also occur in other areas than those where there are many reports of rubella cases from pediatric sentinel clinics (see p. 94 of this issue).
The National Epidemiological Surveillance of Vaccine-Preventable Diseases (see p. 92 of this issue): Measles antibody-positives by the gelatin particle agglutination (PA) test (antibody titer higher than or equal to 1:16) were 75% of 1-year children in the 2004 survey, a 13 point increase over the 2003 survey. The facts that they have increased to 92% among 2-year children, whereas antibody-negatives (susceptibles) were found among heretofore target age group for routine immunization (1-7.5 years) and gradual decrease in antibody titer until the first half of teens are important in future planning countermeasures against measles. The measles vaccination rate of 1-year children was 76% and that of 2-3 years 93%; an increase can be seen from the 2003 survey (1 year 59% and 2-3 years 84%).
Rubella antibody-positives by the hemagglutination inhibition (HI) test (antibody titer higher than or equal to 1:8) were 86% (90% among females and 81% among males). The results were similar to those of 2003. The rubella antibody-positive rate of adult males was as low as 70%. The rubella vaccination rate of 1-4 years was only 75%, lower than the measles vaccination rate. Among females, the rubella vaccination rate of 20-24 years was low (69%) and those of 20-24 years (56%) and 25-29 years (42%) were considerably low among males.
The Preventive Vaccination Law Enforcement Regulation: From April 1, 2006, measles-rubella vaccine has been used and a 2-dose schedule adopted; the first immunization (12-24 months after birth) and the second one (5-6 years, <1 year before primary school entrance) (see http://www.mhlw.go.jp/topics/bcg/tp1107-1.html). A plan has been shown that monovalent vaccine for measles or rubella is scheduled to be included in the vaccine for routine immunization in compliance with the Preventive Vaccination Law. For those who have failed to receive vaccination, such prefectures that are giving supplemental immunization are increasing (see p. 88, 100 & 101 of this issue).
Future problems: Cases of both measles and rubella are on the decrease and it has become difficult to detect a local limited outbreak by the present sentinel-surveillance system. Therefore, it is necessary to introduce a system of notification of all patients and to consider strengthening surveillance such as confirmation with laboratory diagnosis (see CDC, MMWR 54:279-282, 2005). By amendment of the vaccination system, a 2-dose schedule has been introduced. It is necessary to construct strategies to maintain a still higher vaccination rate including countermeasures against those who have failed to receive vaccination (see p. 102 of this issue) and against adult susceptibles toward elimination of measles and CRS (see p. 96 of this issue).
WHO Western Pacific Region aims at elimination of measles by 2012 (http://www.wpro.who.int/media_centre/press_releases/pr_20050922+RCM.htm).