MMR versus Separate Single Vaccines for Measles, Mumps and Rubella
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Some people have suggested that children should be vaccinated against measles, mumps and rubella using separate single vaccines, rather than the combined MMR vaccine. This is based on the supposed link between MMR vaccine and autism spectrum disorders (ASD). The theory is that because MMR contains three different components it somehow "overloads" or weakens the child's immune system, making them more susceptible to developing ASD.
Parents are understandably concerned when links are suggested between a vaccine and a devastating disease such as ASD. Even if the link were only theoretical, giving the three vaccine components separately would seem to be a sensible precaution. The evidence, however, suggests otherwise:
There is no evidence of any association between MMR and ASD
The original supposed link between MMR and ASD was based on a study by the Inflammatory Bowel Disease Study Group (IBDSG), at the Royal Free Hospital in London.1 They described 12 children with ASD where the onset of ASD apparently coincided with receiving the MMR vaccine. The original study stated: "We did not prove an association between measles, mumps and rubella vaccine and the syndrome described". Further studies, including ones carried out by the IBDSG, have not shown any link between MMR and ASD.2
One study, by Kaye et al, found that there was a significant increase in reported cases of ASD in the UK between 1988 and 1999. However, the rate of MMR vaccination remained the same throughout this period. Thus the increase in ASD cases could not be explained by exposure to MMR.3 Another study, by Dales et al, compared the number of cases of ASD with rates of MMR vaccination in California from 1980 to 1994. Again they found a large increase in the incidence of ASD, but only a small increase in MMR vaccination rates. The small increase in MMR rates could not explain the increase in ASD. Furthermore they found that the large increase in ASD incidence occurred before the small increase in MMR vaccination rates.4
Seven international expert groups have reviewed the evidence relating to MMR and ASD. They were all unanimous in their conclusions that the current evidence does not support a link between MMR and ASD.5
Combination vaccines do not overload or weaken the immune system
The MMR vaccine contains 24 different antigens (the chemicals that stimulate the immune system to produce immunity to viruses and other foreign substances). This number of antigens is minute compared to the total number that the immune system is capable of responding to (up to 100,000,000,000).6 Indeed there are fewer antigens in all of the current childhood vaccinations combined then there were in either the single smallpox or older pertussis (whooping cough) vaccines. Likewise we are all exposed to hundreds of times as many antigens every day, in the food we eat, the water we drink and the air we breathe.
Vaccines are designed to strengthen the immune system, not weaken it. In one study from Germany it was found that vaccinated children were not only protected against the diseases for which they had received the vaccines, but also had fewer infections with other bacteria and viruses compared to non-vaccinated children. This was thought to be due to an overall boosting of the immune system by vaccines.7
On the other hand infections with bacteria and viruses often make children more prone to infection with other bacteria or viruses. Measles infection often leads to other infections, such as pneumonia and middle ear infections.
Using three separate vaccines is untested, untried and raises too many unanswered questions
The use of three separate vaccines for measles, mumps and rubella has never been used in any country in the world. There have been no studies done to determine whether or not this approach is safe or effective. Likewise there is no experience with using this approach. This raises a number of unanswered questions: Is this approach safe? Will it protect children against these diseases? What order should the vaccines be given? How much time should be taken between vaccine doses?
In contrast the MMR vaccine has been in use for over 30 years and underwent rigorous studies to ensure that it was safe and effective before it was released for general use. The combined research evidence and decades of experience with MMR has confirmed that it is safe and effective. Indeed, the World Health Organisation recently concluded that MMR is one of the safest vaccines ever produced.
Using three separate vaccines may be less effective and cause more side effects than MMR
The three separate vaccines do not have as long or as rigorous a safety record as MMR. Some varieties of the individual mumps vaccine, in particular, give cause for concern. Some mumps vaccines may contain the Rubini strain of the virus, which was found to be ineffective. Others may contain Urabe strain, which is associated with an increased risk of viral meningitis.2
Separating the vaccines leaves a child exposed to the risk of infection
Leaving a gap between the individual measles, mumps and rubella vaccines means that children are at risk of acquiring one of the other infections before they receive the next vaccine.
Separating the vaccines requires six injections
Two doses of measles, mumps and rubella vaccine are required to ensure maximum protection against these diseases. This means that giving them separately will require six trips to the doctor and six separate injections. Apart from the difficulty of organising six separate visits to the doctor this means that children will have to have an extra four injections unnecessarily. Combining the three vaccines together in the MMR vaccine means fewer traumas for children and fewer visits to the doctor.
MMR is a safe vaccine and protects children against potentially devastating infections. It also prevents the weakening of the immune system that occurs with natural infections. Giving the three vaccines separately is less effective and may be less safe. Given that we have a proven safe, effective vaccine, backed up by more than 30 years experience, it would be unwise to recommend three separate vaccines.
References:
- Wakefield AJ et al. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet 1998; 351: 637-41.
- Elliman DAC and Bedford HE. MMR vaccine: worries are not justified. Arch Dis Childhood 2001; 85: 271-4
- Kaye JA et al. Mumps, measles and rubella vaccine and the incidence of autism recorded by general practitioners: a time trend survey. BMJ 2001; 322: 460-3
- Dales L et al. Time trends in autism and in MMR immunization coverage in California. JAMA 2001; 285: 1183-5
- Medical Research Council. Review of autism research: epidemiology and causes. Department of Health (UK), 2001
- Offit PA et al. Addressing parents' concerns: do multiple vaccines overwhelm or weaken the infant's immune system? Pediatrics 2002; 109: 124-9
- Otto S et al. General non-specific morbidity is reduced after vaccination within the third month of life: the Greifswald study. J Infect 2000; 41: 172-5
