Measles elimination: old and new challenges?

Life attenuated measles vaccines have dramatically reduced measles morbidit y and mortality world-wide. Despite high vaccination coverage, measles outb reaks continue to occur both in developed and developing countries. While s econdary vaccine failure may be responsible for disease in some seroconvert ed individuals, evidence suggests that many more vaccinees who are protecte d against disease may not be fully protected against virus infection. In lo w-income developing countries protection by maternal antibodies seems to er ode faster than previously estimated especially in infants who were born to vaccinated mothers. Problems of infectivity and susceptibility of vaccinee s will be compounded in case wild-type viruses become less sensitive to vac cine induced immunity. These observations suggest that elimination may be m ore easily achieved as long as large proportions of populations are protect ed by wild-type virus-induced immunity. (C) 2001 Elsevier Science Ltd. All rights reserved.