Largest group of children affected by measles outbreak in Wales is 10-18 year olds

The United Kingdom is likely to see more outbreaks of measles as the cohort of children who missed routine vaccination because of safety concerns move into secondary schools, doctors said this week.

The warning came as the number of cases in the Swansea area rose to 808 (as at Thursday 18 April). Public Health Wales said that a total of 77 people had been hospitalised since the beginning of the outbreak.

Uptake of the combination measles, mumps, and rubella (MMR) vaccine fell from 92% in early 1995 to 79.9% in 2002-03, largely because of speculation that it might be linked to autism and Crohn’s disease. MMR uptake is now up again to 92.8% in the UK as a whole, with Scotland and Northern Ireland achieving the World Health Organization target of at least 95% coverage. However, pockets of much lower uptake exist, particularly in London, where the average coverage is only 87%.

Although children of all ages are being affected by the Swansea outbreak, the highest numbers of cases are being seen in those aged between 10 and 18 years. A targeted MMR catch-up campaign has started in schools in the area, and drop-in vaccination clinics have been set up.1

Marion Lyons, director of health protection for Public Health Wales, said, “Although we want children of all ages who have missed vaccinations to catch up now, we are particularly concerned about those aged between 10 and 18.

“These are the children who would have missed vaccination because of concerns about the safety of MMR in the late 1990s. The vaccine is safe, effective, and the only protection against a potentially fatal disease.”

Speaking at a media briefing in London this week, Helen Bedford, senior lecturer in children’s health at the paediatric epidemiology unit at University College London’s Institute of Child Health, said, “There are approaching two million children who are susceptible to measles as they have not received the two doses of MMR vaccine. Last year there were over 2000 confirmed cases of measles in England and Wales, with outbreaks in the north west [of England], north east, and Surrey. There is the potential for further outbreaks.”

She added that the bulk of cases was among teenagers, as young people mixed with a far larger group of children once they moved into secondary school.

Michael Fitzpatrick, a retired Hackney GP, told the briefing, “The MMR autism scare has finished, but we are now dealing with the aftermath of it. Now we are in the position of trying to mop up on those that missed out on two doses of MMR.”

Some children missed out on both doses of the MMR vaccine because of problems with healthcare access. Others chose not to have the vaccine because they thought the risks outweighed the benefits. This second group tended to be concentrated in certain areas of the country. The GP and Conservative MP Sarah Wollaston wrote on her blog this week that in her constituency of Totnes only 70% of 5 year olds were fully protected against measles.2 She also called on homeopathic bodies to issue unequivocal statements that homeopathic products offered no protection against measles.

David Elliman, a specialist in immunisation at the Royal College of Paediatrics and Child Health, said it was important that children received both doses of MMR. “The first dose of MMR gives 90-95% protection against measles, but it takes a second dose to get 99% protection.” Elliman said that the take-up of vaccines was not routinely measured beyond the age of 5. “But what we do know about catch-up campaigns is that they are moderately good in preschool children but not very good among school age children.”

A small investigative study funded by the Medical Research Council recently showed that there were many gaps in teenagers’ understanding of vaccination. The Scottish study of 12 focus groups, involving 59 self selected teenagers, showed that they tended to underestimate the risks from diseases of which they had had little direct experience.3 Another common misapprehension was that only infants were at risk from the serious consequences of meningitis. The study’s author, Shona Hilton, said, “Our study found participants were generally positive about the need for immunisation even if sometimes unaware about the severity and impacts of the diseases vaccines protect against.” She added that it was important to inform teenagers about vaccination, given that they would be the next generation of parents.

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