This week, Public Health Wales warned the measles epidemic in southwest Wales was growing at an "alarming rate" with 432 cases and 51 hospitalizations. The outbreak shows no signs of fading and authorities say there could be 1000 cases before April's end. Officials fear this outbreak could echo the 1999/2000 Dublin outbreak before which vaccination coverage was below 80 percent. Over 1000 children were infected and three died.
One of the great tragedies of the current outbreak is how easily it could have been prevented. After a massive measles-rubella vaccination campaign in 1994, the United Kingdom eliminated measles. Research suggested subsequent sporadic cases were due to imported infection rather than continued circulation of the virus within the United Kingdom.
Unfortunately, vaccine uptake decreased due to now discredited studies linking the MMR vaccine and autism. Measles is one of the most contagious infectious diseases and outbreaks can occur when less than 10 percent of the population is susceptible (unvaccinated or unable to mount an appropriate immune response). Vaccination rates dropped well below 90 percent for many years in England, Wales, and Scotland.
The lag between the start of the decrease in vaccination and the subsequent outbreaks is partially explained by waning maternal antibodies and infection opportunity. Children are protected by their mother's immunity till they are about one year old. Wales recommends a first vaccination at 13 months and a booster at around three and half years. When children miss their vaccines at one and three years old, they may not yet have contact with infected individuals, but when these children enter school and begin to interact with a broader range of their community, they have greater opportunity to be exposed to measles.
In 2008, only about 80 percent of Welsh five-year-olds had received their second MMR vaccine. Those unvaccinated children are now 10 years old, and many of them are likely at risk of contracting measles during this epidemic. Health officials are pleading for parents to immunize their children, but the slight increase seen in vaccinations is insufficient to address the large number of unprotected children.
People with measles are generally infectious for several days before the rash appears. Keeping children home after the rash starts is similar to closing the barn door after the horse has bolted (although it should be noted that the cases continue to be contagious after the rash appears as well).
Measles killed 158,000 globally in 2011. Among the malnourished, very young, or very old, up to 40 percent of cases can have complications, including pneumonia, encephalomyelitis, and permanent neurologic deficits. Even among the healthy, about 20 percent report at least one complication. Before the vaccine was introduced in 1968, about 100 children died from it in England and Wales every year.
The World Health Organization is working to eliminate measles in at least five WHO regions by 2020, but recent outbreaks in Europe, especially in France, show how easily ground can be lost in the fight to eliminate this ancient, deadly, and preventable disease.
Click here for the March 26 2013 Public Health Wales Press Release.