Epidemiology of a workplace measles outbreak dominated by modified measles cases at Kansai international airport, Japan, during august–september 2016

• Published in: Vaccine Vol. 38; no. 32; pp. 4996 - 5001
• Main Authors: Kobayashi, Ayako, Shimada, Tomoe, Tanaka-Taya, Keiko, Kanai, Mizue, Okuno, Hideo, Kinoshita, Masaru, Matsui, Tamano, Oishi, Kazunori
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 06.07.2020; Elsevier Limited
• Subjects: Airports; Catarrh; Contact tracing; Disease Outbreaks; Epidemics; Epidemiology; Fever; Genotype & phenotype; Ground crews; Health risks; Households; Humans; Immunization; Immunoglobulins; Immunosuppression; Infections; Japan - epidemiology; Laboratories; Measles; Measles - epidemiology; Measles - prevention & control; Measles elimination; Measles Vaccine; Modified measles; Outbreak; Outbreaks; Patients; Surveillance; Travel industry; Vaccination; Vaccine; Vaccines; Viruses; Workers; Workplace; Japan; China; Modified measles; Vaccine; Outbreak; Travel industry; Measles elimination
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2020.05.067

•A workplace measles outbreak in a Japan airport started from a symptomatic tourist.•The index case was a classical measles patient with unknown vaccination status.•Most of the affected ground crews were vaccinated and lacked respiratory signs.•No onward measles virus transmission occurred from vaccinated patients.•Tracing contacts of unvaccinated individuals with measles is a priority. In August 2016, a measles outbreak at Kansai International Airport was the first workplace measles outbreak since Japan was verified as having achieved measles-elimination status in March 2015. We investigated this outbreak with a focus on evaluating the ability of vaccinated individuals to transmit measles virus (MV). We considered a case of laboratory-confirmed measles with onset between August 9 and September 29, 2016, among workers of Kansai International Airport. History of vaccination status with measles-containing vaccine (MCV) was confirmed by reviewing records. The potential sources of each MV infection were assessed by interviewing each infected worker about the clinical course of their infection and their behavioral history. Of 30 affected ground crews identified, 16 (53%) were vaccinated with ≥ 1 dose of MCV, 2 (7%) were unvaccinated, and 12 (40%) had an unknown vaccination status. The index case, a patient with classical measles with unknown vaccination status, presumably transmitted MV to all the subsequent 29 cases. The majority of patients (23, 77%; 15 vaccinated, 8 in unknown vaccination status) were diagnosed with modified measles due to mild illness. Modified measles were characterized clinically by signs of catarrh (4/23, 17%) in a few cases, with a median incubation period of 16 (range, 11–21) days. No onward transmission from vaccinated cases was suggested. An overseas traveler who visited the airport with measles symptoms was identified as the possible primary source of this outbreak. The low MV transmission ability of vaccinated individuals was reaffirmed. Contact tracing of vaccinated modified measles cases can be limited to a person at high risk of infection (e.g., households, person with immunosuppression). To maintain measles-elimination status, completing two doses of MCV should be ensured, especially for international travelers and for those who are frequently exposed to these travelers, such as airport workers.