Investigating the immunizing effect of the rubella epidemic in Japan, 2012-14

Nishiura, Hiroshi; Kinoshita, Ryô; Miyamatsu, Yuichiro; Mizumoto, Kenji

doi:10.1016/j.ijid.2015.07.006

Cited by 11 publications

(12 citation statements)

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“…The epidemic in Japan has indicated that a major rubella epidemic can occur with adult patients making up the majority of cases. Given the limited immunising effect of the 2012–2014 epidemic, 24 our findings call for a supplementary vaccination among those remaining susceptible.…”

Section: Discussionmentioning

confidence: 77%

“…The unfortunate tragedy that was identified in Greece in the 1990s 9 has been repeatedly experienced by present day Japan. While a recently published study focused on estimating the impact on the age-specific rubella seroprevalence of the most recent epidemic in Japan from 2012 to 2014, 24 the present study has comprehensively assessed the herd immunity in Japan through the analysis of longitudinal seroepidemiological data, which allowed us to compare between the age-standardised seropositive proportion and the theoretical herd immunity threshold, and, moreover, an elevated age at infection over time was confirmed based on an analysis of reported case data.…”

Section: Discussionmentioning

confidence: 99%

“…Seroconversion, following the convention in Japan (corresponding to results of ≥7.3 IU/mL from ELISA), was defined as an HI titre ≥32. 24 The basic reproduction number, R 0 , acknowledged as the average number of secondary cases generated by a single primary case, was estimated at 6.1 for rubella using an age-structured realistic model. 25 The herd immunity threshold against rubella was calculated by 1−(1/R 0 ), and came to 83.6%.…”

Section: Methodsmentioning

confidence: 99%

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Assessing herd immunity against rubella in Japan: a retrospective seroepidemiological analysis of age-dependent transmission dynamics

Kinoshita

Nishiura

2016

BMJ Open

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ObjectiveWe aimed to epidemiologically assess rubella herd immunity as a function of time, age and gender in Japan, with reference to the recent 2012–2014 rubella epidemic.DesignThis study is a retrospective seroepidemiological analysis.Main outcome measuresThe susceptible fraction of the population was examined as a function of age and time. The age at infection was assessed using reported case data.ResultsWhereas 30 years ago rubella cases were seen only among children, the median (25–75th centiles) age of cases in 2014 was elevated to 32.0 (17.0–42.0) years among males and 27.0 (7.0–37.0) years among females. Susceptible pockets among male birth cohorts 1989–1993 and 1974–1978 were identified, with seropositive proportions of 70.0% and 68.0%, respectively. The majority of female age groups had greater seropositive proportions than the herd immunity threshold, with a minor susceptible pocket for those born from 1989 to 1993 (78.3% seropositive). The age-standardised seronegative proportion decreased to 18.3% (95% CI 16.8% to 19.8%) among males and 15.6% (95% CI 10.0% to 21.2%) among females in 2013, and the immune fraction was not sufficiently below the herd immunity threshold. While the number of live births born to susceptible mothers in 1983 was estimated at 171 876 across Japan, in 2013 it was reduced to 23 698.ConclusionsAn elevated age at rubella virus infection and the presence of susceptible pockets among adults were observed in Japan. Although, overall, the absolute number of rubella cases has steadily declined in Japan, the elevated age of rubella cases, along with increased numbers of susceptible adults, contributed to the observation of as many as 45 congenital rubella syndrome (CRS) cases, which calls for supplementary vaccination among susceptible adults. Assessing herd immunity is considered essential for routinely monitoring the risk of future rubella epidemics and CRS cases.

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Section: Discussionmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Assessing herd immunity against rubella in Japan: a retrospective seroepidemiological analysis of age-dependent transmission dynamics

Kinoshita

Nishiura

2016

BMJ Open

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“…Spatial heterogeneity in susceptibility could act as the key to discriminating the metapopulation model from homogeneous models, and our approach was unable to capture that aspect. It should be remembered that the susceptible pocket was observed mainly among males aged 35–49 years in Japan [ 19 , 20 ], which we intend to address in the forthcoming study with age structured model. The fraction of this “high risk” subpopulation may vary by prefecture and heterogeneous contact patterns would also differ.…”

Section: Discussionmentioning

confidence: 99%

Reconstructing the transmission dynamics of rubella in Japan, 2012-2013

2018

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BackgroundJapan experienced a nationwide rubella epidemic from 2012 to 2013, mostly in urban prefectures with large population sizes. The present study aimed to capture the spatiotemporal patterns of rubella using a parsimonious metapopulation epidemic model and examine the potential usefulness of spatial vaccination.Methodology/Principal findingsA metapopulation epidemic model in discrete time and space was devised and applied to rubella notification data from 2012 to 2013. Employing a piecewise constant model for the linear growth rate in six different time periods, and using the particle Markov chain Monte Carlo method, the effective reproduction numbers were estimated at 1.37 (95% CrI: 1.12, 1.77) and 1.37 (95% CrI: 1.24, 1.48) in Tokyo and Osaka groups, respectively, during the growing phase of the epidemic in 2013. The rubella epidemic in 2012 involved substantial uncertainties in its parameter estimates and forecasts. We examined multiple scenarios of spatial vaccination with coverages of 1%, 3% and 5% for all of Japan to be distributed in different combinations of prefectures. Scenarios indicated that vaccinating the top six populous urban prefectures (i.e., Tokyo, Kanagawa, Osaka, Aichi, Saitama and Chiba) could potentially be more effective than random allocation. However, greater uncertainty was introduced by stochasticity and initial conditions such as the number of infectious individuals and the fraction of susceptibles.ConclusionsWhile the forecast in 2012 was accompanied by broad uncertainties, a narrower uncertainty bound of parameters and reliable forecast were achieved during the greater rubella epidemic in 2013. By better capturing the underlying epidemic dynamics, spatial vaccination could substantially outperform the random vaccination.

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“…As a consequence, the country remains prone to imported cases and experienced a rubella epidemic during 2012-14 (Mori et al, 2017). Moreover, owing to the absence of an identifiable increase in the proportion of rubella antibody-positive individuals following the 2012-14 epidemic (Nishiura et al, 2015), another epidemic began in August 2018. Because the remaining susceptible people are adult male, and owing to the elevated age at infection over time, cases during both the 2012-14 epidemic and the ongoing 2018 epidemic are most frequently seen in adults National Institute of Infectious Diseases, 2018).…”

Section: Introductionmentioning

confidence: 99%

Predicting congenital rubella syndrome in Japan, 2018–2019

Lee

Kayano

Nishiura

2019

International Journal of Infectious Diseases

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A B S T R A C TObjectives: A rubella epidemic has been ongoing in Japan since August 2018. In the present study, we aimed to predict the likely size of a congenital rubella syndrome (CRS) epidemic during 2018-19. Methods: The expected number of CRS cases was estimated using an integral equation based on agespecific incidence of rubella among adult women, the time delay from gestational age of infection to diagnosis of CRS, and distribution of the mothers' age at delivery. We used epidemic data during 2012-14 to parameterize the model and applied this in the prediction for 2018-19. Results: In analyzing the 2012-14 epidemic data, the mean delay from the mother's infection to diagnosis was estimated at 24.2 weeks (95% confidence interval (CI): 20.7, 28.1). Applying the parameterized model, together with the more than 480 rubella cases in women in 2018 as well as delayed mother's age at delivery in 2017, we determined that the expected number of CRS cases would be 9.7 (95% CI: 6.5, 12.5) cases. As the epidemic is ongoing, the cumulative number of CRS cases could potentially reach 96.8 (95% CI: 65.3, 125.5) cases, if rubella cases in adult women rose to 10 times the number by week 49 in 2018. Conclusions: CRS is expected to occur an average of 24 weeks following the mother's infection with rubella virus. Accounting for an increase to 650 cases in women by week 5 in 2019, the expected number of CRS cases during 2018-19 has already exceeded 13 cases, as of week 5 in 2019.

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Investigating the immunizing effect of the rubella epidemic in Japan, 2012-14

Abstract: Susceptible pockets remain in Japan, exposing the country to risk of additional rubella epidemics.

Cited by 11 publications

References 8 publications

Assessing herd immunity against rubella in Japan: a retrospective seroepidemiological analysis of age-dependent transmission dynamics

Assessing herd immunity against rubella in Japan: a retrospective seroepidemiological analysis of age-dependent transmission dynamics

Reconstructing the transmission dynamics of rubella in Japan, 2012-2013

Predicting congenital rubella syndrome in Japan, 2018–2019

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