Almost a decade after it was declared officially eliminated, measles is making a comeback in the United States.

Increasing numbers of uppermiddle-class parents are opting out of the controversial measles, mumps and rubella (MMR) vaccine because of fears over a link to autism.

Although several studies have shown that no link exists between the two, parents panicked by the rumours have exercised their right to prevent their children being vaccinated. It is thought that 2 to 3 per cent of American schoolchildren are under-vaccinated under a non-medical waiver — meaning that their parents are opting out on principle. As a direct result, there have been 72 confirmed cases of measles in ten states this year, more than double the rate last year. Seven more cases were reported in Illinois last week. US health authorities fear that unless confidence in the MMR vaccine is restored the disease could make a devastating return, causing hundreds of deaths and costing billions of dollars.

“Of the people infected by the measles virus, only one had documentation of prior vaccination,” according to America’s Centres for Disease Control and Prevention. “Many of the cases among US children occurred in children whose parents claimed exemption from vaccination due to religious or personal beliefs.”

Before the MMR vaccine was introduced in 1963, America had hundreds of thousands of measles cases every year, with 48,000 hospitalisations, 400 to 500 deaths and about 1,000 patients left with disabilities.

An American-style MMR jab was introduced in Britain in 1988. British health authorities have also seen a reluctance in parents to vaccinate their children because of autism fears.Much to the dismay of pro-vaccine campaigners, both of America’s presidential nominees have contributed to the alarm. In January, John McCain told the mother of an autistic son that “there’s strong evidence that indicates that \ has a lot to do with a preservative in vaccines”; Barack Obama said in April that “the science right now is inconclusive, but we have to research it”.

In 1998 Andrew Wakefield published a paper in the journal The Lancet suggesting that exposure to the measles virus in vaccines could be a contributing factor in autism. Others have speculated that thimerosal — a mercury-laced preservative present in some vaccines — could be responsible for autism diagnoses.

Disease of the past?

4 Days people are contagious before rash shows, and after it disappears

6-20% of measles patients will get an ear infection, diarrhoea or pneumonia

1 in every 1,000 people with measles develops inflammation of the brain

450 measles-associated deaths were reported in the US each year before the vaccine’s introduction

Source: US Centres for Disease Control and Prevention

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