A small decline in the uptake of vaccines could have a dramatic impact on both public health and the economy, research suggests, as concerns about outbreaks of preventable diseases grow in the US and Europe.

The new study reveals that even a 5% drop in uptake of the measles, mumps and rubella (MMR) vaccine among children in the US could result in a threefold increase in measles cases, and cost the public sector millions of dollars.



Experts warn that if MMR vaccination coverage in a community drops below a threshold of around 90-95%, so-called “herd immunity” is eroded, increasing the risk of outbreaks.



“We want to protect children’s health as much as we can and that means not only protecting your own children by vaccinating but also making sure the children around you are also vaccinated,” said Nathan Lo, co-author of the study from Stanford University.

Lo stressed that parents should not be concerned about side-effects of vaccination. “The scientific evidence is very clear, abundantly clear, that these vaccines are safe – there is no relationship with autism,” he said.



Concerns about measles are growing in the UK and the rest of Europe, with both Italy and Romania experiencing large outbreaks this year – a situation which has been linked to the anti-vaccination movement and a misplaced belief that measles is no longer a risk.



“We know that this is a very dangerous disease for young children,” said Andrew Pollard, professor of paediatric infection and immunity at the University of Oxford. “There have been deaths in Europe in the last year because of drops in coverage in various countries.”



Writing in the journal Jama Pediatrics, researchers in the US describe how they explored the impact of a drop in coverage of MMR vaccination, using a computer model based on recent state-level vaccination coverage data, together with data from a handful of counties within each state.

Using recent numbers of measles cases, the team estimated the number of times the disease entered the country and its infectiousness, and then modelled the number of cases that would be expected should MMR vaccination coverage fall. The process was repeated thousands of times to take into account different coverage scenarios within each state, with the model checked for accuracy using historical data on measles cases in England and Wales.



The results reveal that a 5% drop in coverage with the MMR vaccine among children aged between two and 11 in the US would, on average, result in 150 cases of measles a year – a three-fold increase – and lead to additional public sector costs of $2.1m.

But the authors warn the figures are likely to be an underestimate, pointing out that they do not take into account costs around hospitalisation or parental time off work, the impact on infants not yet old enough to receive the vaccine, or unvaccinated adults.



The research follows a number of recent outbreaks in the US, including that among the Somali community in Minnesota this year.



But the authors warn that without action to close non-medical exemption loopholes – present in 18 of the 50 states and thought to apply to 2% of children aged between two and 11 – such outbreaks will become increasingly common.



“Antivaccine groups have gained so much momentum now in the United States that the only thing that is going to reverse this trend, unfortunately, are catastrophic measles epidemics even larger than the ones we have had in Minnesota,” said Peter Hotez, director of the Texas Children’s Hospital centre for vaccine development and co-author of the research.

But Helen Bedford, professor of children’s health at University College London, warned that prohibiting non-medical exemptions would be difficult to enforce, and might even backfire, polarising views and prompting parents to find alternative ways to avoid vaccination of their children, such as home-schooling.



“I don’t think there is any good evidence to show that in any country where you have mandatory vaccination without other things you get good uptake,” she said, arguing instead that it was important parents have a trusting relationship with health professionals who can talk to them about their concerns.



While experts say that mandatory vaccination is not required in the UK, they warn there is no “quick fix” to drops in vaccine coverage, pointing out that even if rates among children bounce back, many individuals will have been left unprotected. “[People] may end up sitting on a timebomb,” said Adam Finn, professor of paediatrics at the University of Bristol.



Pollard agrees. “Immunisation is something that many people think of as personal, but it is actually part of being in a society,” he said. “Our children really have a right to be protected from this entirely preventable disease.”

