How well does the vaccine work?
A recent Cochrane review of 124 studies assessing vaccine effectiveness showed that two doses of MMR vaccine were 96% effective in preventing measles, and one dose was 95% effective in preventing measles.
Two doses of MMR vaccine are also around 86% effective against mumps, and 89% effective against rubella.
Varicella vaccine effectiveness is also very high, with effectiveness estimated to be 93% after one dose and 97% after 2 doses. Since the varicella vaccination programme was introduced in the USA, it is estimated that, in 25 years, more than 91 million varicella cases, 238,000 hospitalisations, and almost 2,000 deaths have been averted.
Public Health England estimates that around 20 million measles cases and 4,500 deaths have been prevented in the UK since a measles vaccine was introduced in 1968.
In addition, they estimate that rubella vaccination has prevented around 1.4 million cases of rubella and 1,300 cases of birth defects and averted 25,000 terminations.
MMRV in other countries
Varicella vaccination is included in the routine vaccine schedules of many other countries, either as a 2-dose or single-dose schedule. These include the USA, Canada, Australia and Germany.
Countries that have introduced programmes have observed a significant impact on cases of varicella and resulting hospitalisations.
In countries introducing a 2-dose schedule, younger children not eligible for vaccination have also been less likely to get the infection because of smaller number of chickenpox cases in the community.
There is also no evidence of increased rates of infection among those who are not eligible for vaccination due to their age following the introduction of a programme.
MMRV and febrile convulsions
Preschool children with a fever (a high temperature), caused by infections including many viruses (such as cold or flu viruses, measles, or chickenpox), can sometimes have a seizure or fit. These are called ‘febrile convulsions’ and can happen with a fever caused by anything.
Febrile convulsions usually last for just a few minutes, during which the child may become stiff, have jerking movements, and not respond to you. Most febrile seizures do not need treatment. But your child will need to be checked in hospital after having a febrile seizure for the first time. They may also need to stay in hospital for a short time.
The NHS advises to make a note of the time the seizure starts and ends, to protect the child’s head during the seizure, remove any dangerous objects nearby, and put the child in the recovery position after the seizure ends.
1 in 25 children will have a febrile convulsion by the time they turn 5, and they are common in children aged between 6 months and 5 years. Children make a full recovery and usually have no long-term side effects. Children “grow out” of and stop having febrile convulsions by the time they start school
Following the first dose of the MMRV vaccine, there is a slightly higher risk of having a febrile convulsion (35 in 100,000), than there is with the first dose of the MMR vaccine (24 in 100,000). However, the chance of a febrile convulsion is much higher if the child is unvaccinated and catches measles (2,300 in 100,000).
Myths about the MMR vaccine and autism
There is no evidence of any link between the MMR vaccine and autism. Autism is a developmental disorder which is usually diagnosed in preschool children. The original research which suggested a link has now been discredited.
The National Autistic Society in the UK has issued a statement saying that ‘there is no link between autism and the MMR vaccine’.
Below is a list of studies and their findings. Click on the links to view the abstracts (summaries) of the scientific papers:
- A Danish study of over 650,000 children found no increased risk for autism after MMR vaccination (Hviid et al., 2019 )
- An analysis of studies involving over 1 million children found no relationship between vaccination and autism. There was no evidence of a link between the MMR vaccine and autism development in children, and the study also found no evidence of a link between thiomersal and autism development (Taylor et al., 2014 ).
- There is no increased incidence of autism in children vaccinated with MMR compared with unvaccinated children (Farrington et al., 2001 ; Madsen and Vestergaard, 2004 ).
- There is no clustering of the onset of symptoms of autism in the period following MMR vaccination (Taylor et al., 1999 ; Mäkelä et al., 2002 ).
- The increase in the reported incidence of autism preceded the use of MMR in the UK (Taylor et al., 1999 ).
- The incidence of autism continued to rise after 1993 in Japan despite withdrawal of MMR (Honda et al., 2005 )
- There is no correlation between the rate of autism and MMR vaccine coverage in either the UK (Kaye et al., 2001 ) or the USA (Dales et al., 2001 )
- There is no difference between the proportion of children with a regressive form of autism (i.e. who appear to develop normally but then lose speech and social skills between around 15 and 30 months) who develop autism having had MMR compared with those who develop autism without vaccination (Fombonne and Chakrabarti, 2001 ; Taylor et al., 2002 ).
- There is no difference between the proportion of children developing autism having had MMR who have associated bowel symptoms compared with those who develop autism without vaccination (Fombonne and Chakrabarti, 2001 ; Taylor et al., 2002 )
- No vaccine virus can be detected in children with autism using the most sensitive methods available (Afzal et al., 2006 ; D’Souza et al., 2006 ).
