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Measles on the increase

Measles featured prominently in the news throughout April following the rapid spread of an outbreak in South Wales. At the time of writing (3 May 2013) 1,039 cases of measles have been reported (but not yet confirmed) in a six month period, with about 40-50 new cases each week. The age group affected mostly are aged 10-18 years.1 As measles is sometimes described as being no more than a benign childhood disease, it may seem surprising that this outbreak has attracted quite so much attention. 

Before a measles vaccine was introduced into the UK in 1968, virtually everyone had caught the disease before the age of 10 years with huge epidemics every two to three years. For example, in 1967, the year before the vaccine came in, there were 460,407 notifications of the disease. Its significant death rate is evidence of the seriousness of this infection, with 99 deaths in 1968.2 Even an uncomplicated case of measles can make children feel very ill, with early symptoms of high fever, cough and cold and conjunctivitis. Koplik spots - tiny white spots like grains of sand on the inside of the cheeks - may also be present. Although these are diagnostic of measles, they do not appear in all cases. 

Between two and four days after the initial symptoms, the rash comprising flat red areas with small raised bumps (maculopapular) appears behind the ears and then spreads down the body. About one in 15 people with measles have complications which include otitis media, pneumonia and convulsions. About one in 1,000 cases have encephalitis.3 The disease is more serious in very young children, in adults, and in individuals who have an underlying condition. Of the 587 confirmed cases in England in the first three months of 2013, 108 (almost 20%) were admitted to hospital.4 There is no specific treatment for measles other than treating symptoms such as with paracetamol or ibuprofen to reduce fever, aches and pains and fluids to avoid dehydration. Antibiotics may be needed to treat secondary bacterial infections, such as pneumonia.3

In Europe in recent years, the death rate from measles has been about one in 1,000-3,000. An outbreak in Dublin in 2000 resulted in 1,500 cases and three deaths.5 In the recent Swansea outbreak there has been one reported death of a young adult, yet although he had measles it is not clear whether measles caused his death. A rare complication of measles is sub-acute sclerosing panencephalitis (SSPE), a progressive neurological complication which comes on some years after an attack of measles and is caused by persistent measles infection. It affects about four per 100,000 people with the disease, but the rate is over four times higher among children who have measles under the age of one year.3

Measles is a particular concern because it is so highly infectious and, as is so apparent in the Welsh outbreak, it spreads rapidly through susceptible populations. The virus is spread through coughs and sneezes and droplets can linger in the air and survive on surfaces for several hours.  

Measles is preventable by vaccination with the measles, mumps and rubella (MMR) vaccine. Preliminary data from the Welsh outbreak suggests 95% protection against measles after one dose of MMR, and 99% after two doses, confirming previous estimates.1  Although rates of vaccination are currently high in young children, with 94% of five-year-olds having had one dose of MMR,4 the children and young people affected by measles in the current outbreak are largely unimmunised. These children and young people were toddlers in the early 2000s at the height of the MMR vaccine safety scare, which was triggered by a publication in a prestigious medical journal. The paper, published in 1998, described 12 children who had autism or autistic symptoms and bowel disease, eight of whom were reported to have started their symptoms shortly after having MMR vaccine.6 Although the authors themselves stated in the paper that they had not proved an association with the conditions and MMR vaccine, it was widely interpreted as showing a link. 

Despite this statement, the lead author went on to make public statements that children should be given single measles, mumps and rubella vaccines at yearly intervals rather than MMR vaccine.7 The topic attracted much interest in the press, and for many years this was largely negative and gave the public the impression that the weight of evidence was equally balanced for and against MMR vaccine.8 Not surprisingly many parents chose not to have their children immunised with the combined MMR vaccine and some sought single vaccines instead. These had never been used in the way suggested and are not recommended as a safe and effective alternative to MMR vaccine. The lack of experience of using the single vaccines in the way suggested, at yearly intervals in young children, means there is no evidence of their safety and efficacy used in this way. Furthermore, because two doses of MMR vaccine are required for optimum protection, this would require six injections if given separately. In the interval between vaccines, children would remain at risk of the infections and as uptake of the more complex completed course may be lower, herd immunity would be lost. The original study suggesting a link between MMR vaccine and autism has now been discredited7 and there is a significant body of robust evidence showing no link between MMR vaccine and autism or bowel disease.9 On the other hand, since no studies have explicitly set out to investigate whether a single vaccine regimen is associated with autism and bowel disease, it cannot be excluded. 

MMR vaccine also provides protection against mumps and rubella, infections which can both give rise to serious consequences. Although rubella is generally innocuous, if a pregnant women catches it in the first 10 weeks of her pregnancy there is a high risk that the developing baby will be damaged and born with congenital rubella syndrome. This can result in foetal death, retarded growth, heart abnormalities, eye problems and sensorineural deafness.3 Previous high uptake of MMR vaccine has led to this serious condition becoming a rare event in the UK, but current measles outbreaks are a warning that susceptibility levels to rubella among teenagers as they approach their childbearing years may also be sub-optimal. Contrary to myths that mumps is only dangerous for boys, it can have serious complications for girls too; both sexes can suffer pancreatitis, meningitis or encephalitis.

In response to the Welsh outbreak and an increase in numbers of cases of measles in England in the first few months of 2013, a MMR catch up campaign targeting 10-16-year-olds who have had either no doses or only one dose of MMR vaccine was announced in April 2013.4 The aim is to ensure that as many of this group as possible have optimum protection by September 2013. Local arrangements for conducting the catch-up campaign will differ, but it is likely that practice nurses will play a vital role. As some parents may have lingering doubts about the safety of MMR vaccine, it will be important to ensure they are aware of the importance of protection against these potentially serious infections and are reassured about the safety and effectiveness of the combined MMR vaccine. 

 

References

1. Wales PH. Measles Oubreak: Data. MMR vaccine effectiveness. 2013. Available at: www.wales.nhs.uk/sitesplus/888/page/66389.

2. Public Health England Health Protection Agency. Measles notifications and deaths in England and Wales,1940-2008. 2013; Available at: www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1195733835814.

3. Royal College of Paediatrics and Child Health. Manual of Childhood Infections. Oxford: OUP; 2011.

4. Public Health England. National MMR vaccination catch-up programme announced in response to measles cases. 2013. Available at: 

www.gov.uk

5. McBrien J, Murphy J, Gill D, Cronin M, O'Donovan C, Cafferkey MT. Measles outbreak in Dublin, 2000. The Pediatric infectious disease journal 2003;22(7):580.

6. Wakefield AJ, Murch SH, Anthony A, Linnell J, Casson DM, Malik M, et al. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet 1998;351(9103):637-41.

7. Dyer C. Lancet retracts Wakefield's MMR paper. BMJ 2010;340.

8. Hargreaves I, Lewis J, Speers T. Towards a better map: Science, the public and the media: Economic and Social Research Council. Swindon: UK; 2003.

9. Demicheli V, Rivetti A, Debalini M, Di Pietrantonj C. Using the 

combined vaccine for protection of children against measles, mumps and rubella. Cochrane Database of Systematic Reviews 2012, Issue 2. Art. No.: CD004407. DOI: 10.1002/14651858.CD004407.pub3