[Medical study of cases diagnosed as rubella in adults]

Model Comparisons of the Cost Effectiveness of Rubella Vaccination Method in Japanese Adults

The number of rubella cases has increased in Japan, especially among adults. Rubella infection in pregnant females can lead to congenital rubella syndrome (CRS). The Japanese government is promoting vaccination to prevent CRS. This study performs a cost-effectiveness analysis of the following four methods: (1) females who wished to become pregnant and partners, with an antibody-titer test; (2) females only, with an antibody-titer test; (3) females and males, without an antibody-titer test; (4) females only, without an antibody-titer test. A decision tree model with a hypothetical cohort of 500 males and 500 females was used for the analysis, and the parameters were obtained from previous studies. The number of avoidances of CRS was defined as the effect. Compared to the case where methods were not implemented, the number of CRS cases that can be prevented by implementing the methods was 0.0115589 by (1) and (3) and 0.0147891 by (2) and (4). The cost effectiveness of (1) to (4) was 287,413,677 JPY, 135,050,529 JPY, 388,524,974 JPY, and 197,744,219 JPY, respectively (1 JPY = 0.00963247 USD). Method (2) was the most cost-effective and did not change by sensitivity analysis. We conclude that the vaccination for females only with an antibody-titer test is recommended.

Conjunctivitis, the key clinical characteristic of adult rubella in Japan during two large outbreaks, 2012-2013 and 2018-2019

Background

Rubella virus infection mainly causes illness with mild fever, rash, and lymphadenopathy in children; however, the clinical characteristics of adult rubella are not well-known.

Methods

An observational study was conducted to compare the characteristics between adult rubella and adult non-rubella among participants aged ≥18 years, with suspected symptomatic rubella. Participants were screened for rubella-specific IgM expression using an enzyme immune assay kit, at a tertiary care hospital in Japan during two outbreaks (January 2012–December 2013 and January 2018–March 2019). Adult rubella diagnosis followed strong positive or paired rubella-specific IgM expression or positive rubella-specific reverse-transcription-polymerase chain reaction. Patients aged <18 years or with clinically suspected rubella with weak or negative IgM expression were excluded.

Results

Overall, 82 adult rubella and 139 adult non-rubella, with a median age (interquartile range) of 31 (25–41) years and 34 (27–42) years, respectively, were included. Multivariate analysis showed that conjunctivitis (odds ratio 80.6; 95% confidence interval 13.4–486.3; P <0.001) and male sex (odds ratio 7.1; 95% confidence interval 1.8–28.1; P = 0.005) were significantly associated with adult rubella. Among men born from 1962 to 1979 (high-risk population, n = 68), conjunctivitis also showed a significant association with adult rubella in the multivariate analysis (odds ratio 24.2; 95% confidence interval 1.1–553.7; P = 0.046) as these patients were not included in the national vaccination program. There was no difference in the clinical characteristics between one-time vaccination (n = 11) and no vaccination (n = 8) patient in the adult rubella group.

Conclusions

Conjunctivitis was the key clinical symptom associated with adult rubella. For the early diagnosis of adult rubella, clinicians should focus on assessing conjunctivitis in patients.

A case of adult rubella in Japan

We report the case of a 32-year-old Japanese female who presented with a mild sore throat, rash and posterior cervical and posterior auricular lymphadenopathy. She was diagnosed with rubella. Japan has experienced multiple outbreaks of rubella in recent times. Travelers to Japan should consider getting vaccinated for rubella.