Not enough children are being immunised against measles, mumps and rubella to ensure adequate control of the diseases, finds a large study of children born 2000-2002 in the UK.
Researchers at the UCL Institute of Child Health and Great Ormond Street Hospital for Children found that 88.6% of children had been immunised with MMR by the age of three. 5.2% had received at least one of the single vaccines, and 6.1% were unimmunised. Of the 634 children who had received at least one single vaccine, just over half (52%) had received all three.
The study published on bmj.com today emphasises that this is well below the level needed to prevent outbreaks of the diseases. Although the uptake of MMR vaccine has increased recently, there have been more cases of measles in 2007 than in any year for the past decade so further improvement is essential, say the authors.
The combined measles, mumps and rubella vaccine (MMR) was introduced in 1988 in the UK. Following the publication of research in 1998, which was interpreted as suggesting a link between the vaccine and autism and bowel disease, uptake fell from a high of 92% in 1995 to a low of 79% in 2003.
The UCL researchers explored social, economic and cultural factors associated with uptake as well as parents' reasons for not having MMR vaccine for the 14,578 children in the study. They only looked at uptake of the first dose of MMR vaccine. Uptake of the second dose is much lower, say the authors, but is necessary to ensure all children are adequately protected.
Children who had not received any MMR vaccine were more likely to come from a large family, their mother was more likely to smoke, and was either younger (under 20) or older (over 34) than average when she gave birth.
In contrast they found that parents who chose single vaccines were significantly more likely to be white, well educated, affluent, older, and have just one child compared with parents who fully immunised their child. The authors stress that single antigen vaccines are not licensed for use in this country and are not a good substitute for the combined MMR vaccine. They are only available on a private basis.
Of the parents who chose not to have their child immunised with the MMR vaccine, nearly three quarters (74.4%) said it was due to a "conscious decision." Common reasons given were being too scared, thinking the vaccine was too dangerous, links with autism, and negative media attention.
Although MMR uptake in this study is high, say the authors, a substantial proportion of children remain susceptible to avoidable infection, largely because parents consciously decide not to immunise.
They conclude, as does an accompanying editorial, that to achieve the best possible control of vaccine preventable diseases, a variety of measures may be required to target the different groups where uptake of the vaccine is low.