Population-based study of a free rubella-specific antibody testing and immunization campaign in Chiba city in response to the 2018–2019 nationwide rubella outbreak in Japan

Figures & data

Table 1. History of the national immunization program for rubella in Japan

Birth date	Vaccine	Schedule of national immunization program
		Men	Women
June 2, 2006–	MR-MR	Two doses(1^st dose: in childhood 2^nd dose: 1 year before entering elementary school)
Apr. 2,2000–June 1, 2006	Rubella-MR	Two doses(1^st dose: in childhood 2^nd dose: 1 year before entering elementary school)
Oct. 2, 1987–Apr. 1, 2000	Rubella*	One dose(individual vaccination in childhood)**
Apr. 2, 1979–Oct. 1, 1987	Rubella*	One dose(individual vaccination in junior high school students)
Apr. 2, 1962–Apr. 1,1979	Rubella*	None	One dose(group vaccination in junior high school students)
–Apr. 1, 1962		None

*The measles-mumps-rubella (MMR) vaccine was introduced in Apr. 1989; however, this vaccine was terminated in Mar. 1993 due to the adverse effect of aseptic meningitis.

** The measles-rubella (MR) catch-up immunization campaign was designed in 2008 to be conducted for five years to give an additional dose of the MR vaccine to children born from April 2, 1990 to April 1, 2000.

Table 2. Epidemiology in Japan and Chiba city and comparison of the nationwide campaign and Chiba city campaign

	Japan	Chiba city
Population (Sep.30, 2019)	126,167,000	972,500
Men born between April 2, 1962 and April 1, 1979	12,160,000	138,800
Number of rubella infections (2019)	2,306	48
Number of CRS cases (2019)	4	0
Summary of campaign	Nationwide campaign	Chiba city campaign
Rubella-specific antibody testing
Target of this campaign	Men born between April 2, 1962 and April 1, 1979	Citizens who ●・want to become pregnant ●・are husbands or families of pregnant women or women who want to become pregnant
Subsidizing rate	100% free	100% free
Start date	April 2019 (June 2019 in Chiba city)	●・April 2014 (women wanting to become pregnant) ●・October 2018 (their husbands) ●・April 2019 (their families)
Measles–rubella vaccination
Target of this campaign	People who received the antibody campaign and did not have sufficient rubella specific antibodies	Citizens who did not have sufficient rubella-specific antibodies (regardless of whether the results were obtained through the Chiba city campaign)
Subsidizing rate	100% free	100% free
Start date	April 2019 (June 2019 in Chiba city)	November 2018

CRS, Congenital rubella syndrome

Table 3. Seroprevalence of rubella-specific antibodies from the nationwide campaign data

		n (%)
	Number of participants	HI < 1:8	HI ≤ 1:8	HI ≤ 1:16
Total	8273	1207 (14.6)	1944 (23.5)	2487 (30.1)

HI, hemagglutination inhibition test

Table 4. Seroprevalence of rubella-specific antibodies from the Chiba city campaign data classified according to sex and age

			n (%)
	Age (y.o.)	Number of participants	HI < 1:8	HI ≤ 1:8	HI ≤ 1:16
Total		6103	572 (9.4)	1202 (19.7)	2067 (33.9)
Men	Total	3256	399 (12.3)	735 (22.6)	1130 (34.7)
	0–9	5	2 (40)	3 (60)	4 (80)
	10–19	3	1 (33.3)	1 (33.3)	2 (66.7)
	20–29	533	55 (10.3)	153 (28.7)	264 (49.5)
	30–39	1708	167 (9.8)	341 (20)	544 (31.9)
	40–49	726	131 (18)	180 (24.8)	243 (33.5)
	50–59	257	41 (16)	53 (20.6)	66 (25.7)
	60–69	15	1 (6.7)	3 (20)	4 (26.7)
	70–	9	1 (11.1)	1 (11.1)	3 (33.3)
Women	Total	2847	173 (6.1)	467 (16.4)	937 (32.9)
	0–9	12	2 (16.7)	5 (41.7)	8 (66.7)
	10–19	18	3 (16.7)	8 (44.4)	11 (61.1)
	20–29	887	59 (6.7)	177 (20)	366 (41.3)
	30–39	1421	90 (6.3)	227 (16)	435 (30.6)
	40–49	374	9 (2.4)	26 (7)	80 (21.4)
	50–59	88	5 (5.7)	13 (14.8)	22 (25)
	60–69	38	4 (10.5)	9 (23.7)	13 (34.2)
	70–	9	1 (11.1)	2 (22.2)	2 (22.2)

y.o, years old; HI, hemagglutination inhibition test

Figure 1. The seronegative proportions from both campaigns evaluated at three different titer cutoff values and stratified based on age and sex

Each black, striped, and white bar indicates the percentage of participants whose rubella-specific antibody titers were <1:8, = 1:8, and = 1:16 according to the HI test results, respectively. The seronegative proportions were higher in young people, particularly those in their 20s, according to an HI ≤ 1:16 cutoff value (men: 49.5%, women: 41.3%); however, the seronegative proportions were higher in men in their 40s and 50s when an HI cutoff value of <1:8 was used (14.8% and 16.0%, respectively). y.o, years old; HI, hemagglutination inhibition test.

Table 5. Number of people who had received the measles-rubella vaccine in the nationwide campaign and the vaccination rate of the total population of the target ages in Chiba city

	Number ofparticipants	Vaccination rate of the total populationof the target ages in Chiba city (%)*
Total	1517	2.4

* The number of men born between April 2, 1972 and April 1, 1979 in Chiba city as of September 30, 2019 (62,943 people).

Table 6. Number of people who had received the measles-rubella vaccine during the Chiba city campaign classified according to sex and age

	Age (y.o.)	Number ofparticipants
Total		3593
Men	Total	1368
	0–9	4
	10–19	11
	20–29	272
	30–39	495
	40–49	463
	50–59	91
	60–69	22
	70–	10
Women	Total	2225
	0–9	7
	10–19	73
	20–29	843
	30–39	1043
	40–49	171
	50–59	67
	60–69	18
	70–	3

y.o, years old

Figure 2. The percentage of participants in the nationwide campaign who visited medical facilities on each day of the week

The black bar indicates the percentage of participants who visited medical facilities on Saturdays (rubella-specific antibody testing: 20.7%, measles–rubella vaccination: 34.8%). The participants in the nationwide campaign tended to visit medical facilities on Saturdays.