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

Ayako Kobayashi; Tomoe Shimada; Keiko Tanaka-Taya; Mizue Kanai; Hideo Okuno; Masaru Kinoshita; Tamano Matsui; Kazunori Oishi

doi:10.1016/j.vaccine.2020.05.067

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

Vaccine. 2020 Jul 6;38(32):4996-5001. doi: 10.1016/j.vaccine.2020.05.067. Epub 2020 Jun 10.

Authors

Ayako Kobayashi¹, Tomoe Shimada², Keiko Tanaka-Taya², Mizue Kanai¹, Hideo Okuno², Masaru Kinoshita³, Tamano Matsui², Kazunori Oishi⁴

Affiliations

¹ Field Epidemiology Training Program, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjyuku, Tokyo 162-8640, Japan.
² Infectious Disease Surveillance Center, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjyuku, Tokyo 162-8640, Japan.
³ Medical Administration Division, Public Health and Medical Administration Office, Department of Public Health and Medical Affairs, Osaka Prefectural Government, Otemae, Chuo, Osaka 540-8570, Japan.
⁴ Infectious Disease Surveillance Center, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjyuku, Tokyo 162-8640, Japan; Toyama Institute of Health, Imizu, Toyama 939-0363, Japan. Electronic address: toyamaeiken1@chic.ocn.ne.jp.

PMID: 32535017
DOI: 10.1016/j.vaccine.2020.05.067

Abstract

Objectives: 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).

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: Measles elimination; Modified measles; Outbreak; Travel industry; Vaccine.

Publication types

Case Reports
Research Support, Non-U.S. Gov't

MeSH terms

Airports*
Disease Outbreaks
Humans
Japan / epidemiology
Measles Vaccine
Measles* / epidemiology
Measles* / prevention & control
Vaccination
Workplace

Substances

Measles Vaccine