Rise of the Measles

I was chatting to my colleagues during a brief respite in our Friday duty session last week about measles. A mix of ages and experience, but not one of us had seen a case of measles in our clinical careers. The fact that none of us had seen a case of measles highlights what a success story the measles immunisation programme had been in the UK. Or at least until recently….

The current widely publicised outbreaks of measles are a genuinely sad state of affairs, given how far we had come in keeping this disease under control. Barring a slight blip in the 2000s (thanks in large part to the ‘study that shall not be named’..Lancet 1998, I’m sure you will all remember..) there had been a generally steady reduction in measles in the UK since the introduction of the measles vaccination in 1968, followed more latterly by the MMR vaccine. Indeed, by 2016 and 2017 the WHO declared measles eliminated in the UK. But as discussed in a BJGP review (BJGP 2023; 73 (734)) by 2019 vaccination rates were dropping, measles incidence was rising, and whilst there was an inevitable drop in cases during the COVID pandemic, by 2023 cases were rising steeply. By July 2023 there was enough concern to trigger a a warning by the UKHSA of the risks of a major measles outbreak in London, due to poor vaccine uptake.

In 2022/23 coverage of 2 MMR vaccines by age 5 in England had dropped to <85%, the lowest level since 2010/11 and well below the 95% level required for stable herd immunity, with large regional disparities. Although London remains the most vulnerable area with the lowest vaccine uptake, it is the outbreak in the West Midlands that has hit the headlines (BMJ 2024;384:q113). Birmingham Children’s Hospital has treated >50 children with measles in the last month, with the number of lab confirmed measles cases (1.10.23-18.1.24) in the West Midlands hitting 216, the vast majority in unvaccinated children aged under the age of ten. To put this in context that is more lab confirmed cases (209) than in the whole of England last year (1.1.23-30.11.23).

There is understandable concern that cases could rise steeply across the UK. Measles is highly infectious with an R0 number (the number of cases one index case will generate in a susceptible population) of 15-20. It is thought that, if susceptible, spending 15 minutes in a room with someone with measles confers a 90% risk of transmission. Together with the fact that people are often infectious for 4 days before the rash appears, this is a disease that can spread quickly. As is often the case with successful vaccination programmes, there is a double edged sword that once incidence declines it is very easy to forget what all the fuss was about when the illness was more prevalent. Whilst thankfully death from measles is rare in the UK, this is not a disease you would want to get. Whilst the acute illness is unpleasant enough, measles knocks the immune system meaning a higher risk of secondary infections. Viral pneumonitis, secondary bacterial infections and tracheobronchitis (‘measles croup’) are common complications, and as seen from the West Midlands experience, a lot of these children end up unwell enough to need hospital admission. Rarer serious complications such as encephalitis (0.05%-0.1%) and subacute sclerosis pan encephalitis (SSPE ~0.01%) are likely to be seen more as incidence increases.

So for those of us inexperienced in dealing with measles, what do we need to look out for, and how do we manage this disease? We summarise the assessment and management in our KISS, incorporating recent updated guidance from the UKHSA Jan 2024 and NHSE Jan 2024. It goes without saying, anything we can do to promote MMR uptake in unvaccinated populations could make a huge difference to controlling the spread of the disease.