Measles transmission risk during commercial air travel

Measles transmission on aircraft has been well-documented, and many countries perform contact investigations after exposure events during air travel. This review summarized and updated available evidence for measles transmission risk during commercial air travel to inform best practices for public health response after such exposures.

We searched eight databases for articles and pre-prints about measles and air travel published during 2004-2023. Reviewers screened for articles that contained primary data about measles exposure events on commercial flights. Two reviewers used a piloted data extraction template to collect information from each article, including flight characteristics, approach to contact investigation, and outcomes. Risk of bias was assessed using the Mixed Methods Appraisal Tool.

The initial literature search identified 196 articles, of which 19 met the inclusion criteria. These articles described contact investigations performed for ≥182 flights, which identified 70 secondary cases associated with 144 index cases. In articles where the contact investigation did not include the whole plane, many secondary cases were seated outside the contact zone, as defined by the investigation. Among secondary cases where vaccination status was known, 73% (40/55) were unvaccinated, and vaccination rates among cases < 18 years of age were especially low (3/18, 17%). Uptake of post-exposure prophylaxis was low in the few articles that reported this information.

Measles transmission on aircraft is an established risk, especially for persons that are unvaccinated, and can affect passengers seated outside of the rows immediately around the index case. The available information suggests many barriers to provision of post exposure prophylaxis, and routine vaccination likely remains the best protection against measles outbreaks associated with air travel. However, most studies were designed and reported in a way that did not support robust analysis of the best approaches to contact investigation or the most effective way to prevent secondary cases.