Measles outbreaks in US and Canada show that MMR vaccines are needed more than ever – an expert in children’s health explains
Measles is one of the most challenging diseases to control. It requires a sustained uptake of well over 90% of two doses of a measles-containing vaccine such as MMR. But since the COVID pandemic, there has been a decline in uptake of routine vaccines in many countries including the US, Canada and Europe, resulting in outbreaks of the disease.
For instance, despite eliminating measles in 2000, the US experienced an outbreak in April 2025. In Texas, the centre of this outbreak, 57 people were hospitalised and two unvaccinated school-aged children died.
Canada has also exerienced its largest measles outbreak in 14 years, while last year, England experienced an outbreak of almost 3,000 confirmed cases and one death.
Before the measles vaccine was introduced in the UK in 1968, virtually every child caught the highly infectious disease and hundreds of thousands of cases were reported each year. In a peak year, there were over 100 measles-related deaths.
Twenty years after the introduction of a measles-only-vaccine, it was replaced with the combination vaccine MMR which also gives protection against mumps and rubella. The aim of this vaccine is to eliminate all three infections. There has been varying success in achieving this aim.
Rubella – also known as German measles – is a very mild infection, but can be devastating if caught in the early stages of pregnancy. Fortunately, it is now a rare condition in the UK thanks to MMR.
In rare cases, mumps can cause complications such as meningitis and hearing loss – but it too is now much less common than pre-MMR vaccine.
Measles can be fatal and is highly contagious, so it’s much more difficult to control than most other infections. It has a high rate of complications, including pneumonia and inflammation of the brain.
One vaccine dose gives about 95% protection against infection. But, because measles is so contagious, 95% uptake of two doses is needed to prevent outbreaks. Achieving such high uptake in all communities – and importantly, sustaining this high uptake once reached – is challenging.
Vaccine hesitancy
In 1998, research published in the medical journal The Lancet implied a link between the MMR vaccine and autism. This received intense media coverage and, not surprisingly, many parents decided not to have their children vaccinated.
The research was subsequently discredited and the study formally retracted by The Lancet in 2010. Since then, many studies have found no link between the MMR vaccine and autism, but for some parents, these fears persist.
Currently in England, vaccine uptake rates are too low. Only 89% of two-year-old children have had their first dose of MMR vaccine, and 83.9% have had two doses by the age of five. This means large numbers of unvaccinated children: more than 10% of children in each year group remain unprotected.
Vaccine uptake varies widely around the country. In some parts of London, as many as half the children starting school at five years of age have not had the two doses of vaccine needed for best protection.
Not only are current vaccine uptakes too low to prevent outbreaks of measles, but many years of less-than-optimal vaccine uptake – including among young adults who weren’t vaccinated as infants because of the autism scare – has resulted in a large number of unprotected people. The impact of COVID also resulted in many young children missing their vaccines.
Many factors affect whether people are vaccinated or not, including how, where and when vaccination services are provided, as well as behavioural and social factors. For example, vaccine hesitancy, defined by the World Health Organization as a “delay in acceptance or refusal of vaccination despite availability of vaccination services”, is frequently blamed for people not getting vaccinated. Research suggests that vaccine hesitancy has increased since the COVID pandemic – even for vaccines such as MMR that have led to the near-eradication of some infectious diseases.
In England, surveys are conducted regularly to investigate the views of parents of young children regarding vaccination. The most recent survey, conducted in 2023, showed that 84% of parents reported they considered vaccines to be safe – a [reduction from the previous year].
These findings are reflected in other studies. Since COVID, some parents have reported that the pandemic has affected their views, either making them keener to have their children vaccinated or increasing their concerns about vaccination.
Given the intense scrutiny and widespread discussion about vaccination that took place during the pandemic, this is not surprising. Unfortunately, due to pressures on general practice and other health services – resulting in a 40% reduction in the number of health visitors in England since 2015 – these trusted sources of advice about vaccination have become less easily available. In this context, people may turn to other sources of less reliable information, such as social media.
Although there is no robust evidence to show that health misinformation would stop a parent who was going to have their child vaccinated from doing so, it can be influential for people with existing concerns.
Accessing services
A large study using vaccination records of over ¾ million children born between 2000 and 2020 found that children born in the UK’s most deprived areas were less likely to receive the MMR vaccine. Parents also report having difficulty making or attending appointments as a barrier to vaccination.
Addressing these obstacles requires a multi-pronged approach, ensuring parents are sent vaccination reminders and are able to attend appointments at suitable times and locations. This may mean holding vaccination clinics at places other than the general practice and at weekends and evenings.
Work should be done with local communities to establish what works best for them to improve access to immunisation. Opportunistic immunisation is also important: when attending health services for another reason, unvaccinated children could be offered vaccines on the spot.
Urgent action is needed to improve vaccine uptake – and it requires sustained commitment and increased funding.
Helen Bedford receives funding from National Institute for Health and Care Research.