Disease
Measles is a highly contagious infection; before vaccines became available, this disease affected most people by the time of adolescence. In 2005, measles still affected nearly 21 million persons, and the number of global measles deaths was estimated to be 345 000. Common complications include middle-ear infection and pneumonia. Transmission, which is primarily by large respiratory droplets, increases during the late winter and early spring in temperate climates, and after the rainy season in tropical climates.
Occurrence
Measles occurs worldwide in a seasonal pattern. However, following the introduction of large-scale measles immunization, far fewer cases now occur in industrialized countries and indigenous transmission has virtually stopped in the Americas. Epidemics may still occur every 2 or 3 years in areas where there is low vaccine coverage. In countries where measles has been largely eliminated, cases imported from other countries remain an important continuing source of infection.
Risk for travellers
Travellers who are not fully immunized against measles are at risk when visiting countries or areas where vaccine coverage is incomplete.
Vaccine
The measles/mumps/rubella triple (MMR) or measles/rubella (MR) vaccine is given in many countries instead of monovalent measles vaccine. In industrialized countries, measles vaccination is usually given at the age of 12–15 months, when seroconversion rates in excess of 90% are expected. In most developing countries, high attack rates and serious disease among infants necessitate early vaccination, usually at 9 months of age, despite the relatively low (80–85%) seroconversion rates following vaccination in this age group. To ensure optimum population immunity, all children should be given a second opportunity for measles immunization. Although generally administered at school entry (age 4–6 years), the second dose may be given as early as one month following the fi rst dose, depending on the local programmatic and epidemiological situation. Special attention must be paid to all children and adolescent/young adult travellers who have not been vaccinated against measles at the appropriate time. Measles is still common in many countries and travel in densely populated areas may favour transmission. For infants travelling to countries where measles is highly endemic, a dose of vaccine may be already given at 6 months of age. However, children who receive the fi rst dose between 6 and 8 months should subsequently receive the two doses according to the national schedule. Older children or adults who did not receive the two lifetime doses should consider this before travel. It is generally recommended that individuals with a moderate degree of immune defi ciency receive the vaccine if there is even a low risk of contracting measles infection from the community. There is a low level of risk in using measles vaccine in immunocompromised HIV-infected individuals. Where the risk of contracting measles infection is negligible, physicians who are able to monitor immune status, for instance CD4 counts, may prefer to avoid the use of measles vaccine.