To the Editor—Measles outbreaks have been reported in the Hong Kong Medical Journal in the past 2 years.1 2 Such outbreaks occur worldwide, including in countries where measles was previously considered eliminated. In March 2019, there was a measles outbreak at Hong Kong International Airport involving airport workers, some with documented evidence of at least two doses of measles vaccinations.3 Fortunately, the patients were all relatively young adults who experienced with mild symptoms, and the basic reproduction number of these cases was not high. In response to this outbreak, control measures at the airport included a vaccination programme and measles antibody testing for airport staff. The Hong Kong childhood immunisation schedule was also revised, so that the second dose of the MMRV (measles, mumps, rubella and varicella) vaccination is given at age 18 months (previously given at age 6 years) to enhance protection against measles.

Measles vaccination uptake rate is declining due to pockets of unvaccinated communities and anti-vaccination movements, both of which might have contributed to the recent outbreaks. To eliminate measles, a continuously high (>95%) level of vaccination coverage is required in all areas. Most recent outbreaks of measles in developed countries have been imported cases; thus, they are closely linked to the aviation industry. Early recognition of disease outbreak could prevent a global pandemic. Therefore, it is crucial to have contingency plans at every airport to prevent the spreading of contagious diseases. Travellers should ensure their vaccination status is up-to-date with two doses of measles vaccination; infants from 6 months of age should receive a supplementary dose of measles vaccine if they are travelling to areas with measles outbreaks.4 Affected patients, especially school-age children, should be isolated and quarantined at home for at least 4 days from the appearance of rash.

The 2019 measles outbreak saw a substantial increase in the number of measles cases reported worldwide relative to 2018. Such outbreaks will occur again if we do not learn from the past. The only hope to truly defeat measles is for humankind to work together.

The authors had full access to the data, contributed to the study, approved the final version for publication, and takes responsibility for its accuracy and integrity.

As an Editor of the Journal, KL Hon was excluded from the review process for this letter. The other author has disclosed no conflicts of interest.

1. Hon KL, Leung AK, Leung K, Chan GC. Measles outbreak at an international airport: a Hong Kong perspective. Hong Kong Med J 2019;25:331-3. Crossref

2. Leung AK, Hon KL, Leong KF, Sergi CM. Measles: a disease often forgotten but not gone. Hong Kong Med J 2018;24:512-20. Crossref

3. Centre for Health Protection, Hong Kong SAR Government. Daily update on measles situation in Hong Kong. Available from: https://www.chp.gov.hk/files/pdf/daily_update_on_measles_cases_in_2019_eng.pdf. Accessed 6 Dec 2019.

4. World Health Organization. WHO advice for international travel in relation to measles. 2019. Available from: https://www.who.int/ith/WHO-advice-for-international-travel-in-relation-to-measles.pdf?ua=1. Accessed 6 Dec 2019.