Liam Drew in Nature:
In 2015, the World Health Organization (WHO) declared that the United Kingdom had eradicated the infectious viral disease rubella. The following year, it similarly designated the country as measles-free after confirmed cases numbered fewer than 125 for the second consecutive year. Immunization rates in UK children were high at that time. They had slumped to a nadir in the mid-2000s following the false assertion in 1998 that the measles, mumps and rubella (MMR) vaccine was linked to autism. But by 2016, more than 95% of the country’s 5-year-olds had received one dose of MMR, and roughly 85% had received the pre-school booster that maximizes immunity. When 95% of a population is immune to measles, the disease cannot spread. This is known as herd immunity, and it is the cornerstone of the WHO’s long-held plan to eradicate measles globally. Achieving this would rid the world of a very serious disease, for which 1 in 1,000 cases is fatal. In 2010, eradication was considered achievable by 2020. But that time is almost here, and the disease is not close to being eradicated. In fact, it is on the rise.
During the first half of this year, Europe had 90,000 cases of measles — more than 17 times the number reported in the whole of 2016. In August, the United Kingdom lost its measles-free status (as did Albania, Greece and the Czech Republic). The United States, which is currently experiencing the highest number of measles cases since 1992, is also at risk of losing the measles-free standing that it has held since 2000. The resurgence of measles is a symptom of falling rates of immunization against infectious disease. “When immunization rates drop and herd immunity frays, it’s always measles that comes back first,” says Paul Offit, a paediatrician specializing in infectious disease at the Children’s Hospital of Philadelphia, Pennsylvania. “Measles is the canary in the coal mine.”