LAUSR

The region of the Americas is currently experiencing its largest measles outbreak since measles elimination was declared in 1999 and Europe is experiencing unprecedented numbers of measles cases in the current era of measles control. The declaration of measles elimination from the region of the Americas was an historic milestone, as the first WHO region to eliminate measles and proof that measles and rubella elimination could be achieved through high routine coverage, regular supplementary immunisation activities and a high-quality case-based surveillance with a rapid, co-ordinated outbreak response. The extent of the current outbreak is a setback to the WHO’s global measles and rubella elimination goals and persistence of this current outbreak for longer than 12 months will result in the affected countries losing their elimination status. The resurgence of measles across Europe highlights the impact of ongoing insufficient two-dose coverage in affected countries. Ceccarelli and colleagues estimated a seroprevalence of measles IgG antibodies of 80–88% among recent migrants from the WHO African region, while sub-optimal, these rates are greater than WHO coverage estimates from the region and on par with coverage reported in some European receiving countries. Despite record numbers of migrants arriving in Europe, the contribution of migration on the current epidemiology of measles in Europe is minimal. However, immigrants from within and outside Europe are a growing population group and face barriers to accessing immunisation and other health services and strategies to reach migrant populations and provide catch-up immunisation are needed. For travel health practitioners in countries without endemic measles, these outbreaks are a reminder that MMR is an important travel vaccine. All travellers should be assessed for immunity, particularly if travelling to countries experiencing measles outbreaks. Two doses of MMR vaccine, administered at least 28 days apart, is recommended for all children aged 12 months and over and for adolescents and adults without documented two-dose coverage or measles immunity. Adults born before 1957 (USA), 1968 (Australia) and 1970 (UK, Canada), depending on the commencement of universal measles immunisation programmes and subsequent decline in measles transmission, are considered presumably immune through acquired natural immunity. For infants travelling to destinations experiencing high rates of measles a single dose from as young as 6 months of age is recommended for infants in the USA, the UK and Canada or 9 months of age in Australia. For infants receiving an early dose, two additional doses are recommended to commence from 12 months of age (except in Australia), where only 1 additional dose is recommended. While there are reports of measles importations resulting from international adoptions and humanitarian entrants, the majority of international travel and subsequently, the majority of importations of measles are in short-term travellers. Large, sustained outbreaks in countries with sub-optimal immunisation coverage, such as many countries in Europe, result in regular incursions by travellers into regions that have eliminated measles, some resulting in local outbreaks. One of the criteria set by the WHO for monitoring the maintenance of measles elimination is a rate of locally acquired cases of <1 per million population. However, this is difficult to achieve for countries with high rates of international travel, particularly during ongoing outbreaks in popular destinations. Rapid control efforts are required to prevent large outbreaks occurring from the importation of measles by an international traveller, which is costly and time consuming for public health authorities. The majority of imported cases of measles are young adults, who are more likely to travel and less likely to be vaccinated than children. While reported childhood immunisation coverage rates demonstrate high two-dose MMR coverage of >90% in countries such as Australia, the USA and Canada, this only provides data on the current programme, with historical coverage limited for older age groups and often not available for adults. Young adults are an important group at risk of underimmunisation, as a result of lower coverage of measles vaccine during childhood in an era of decline disease rates and singlevaccine dose recommendations. For those in the UK, young adults born between 1980 and 1990 are considered at risk of being unimmunised or partially immunised and for Australia, this includes those born between 1972 and 1978, identified in national serosurveys to have significantly lower population seroprevalence. In addition, adolescents and young adults were found to have a higher proportion of equivocal results, indicating potential for breakthrough disease. Migrant travellers visiting friends and relatives may be at increased risk of acquiring measles during travel. Measles in vaccine recipients is reported in enhanced surveillance, with time since vaccination and