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expert reaction to UKHSA risk assessment for measles resurgence in the UK, reporting that London is at risk of measles outbreaks

A press release from the UK Health Security Agency (UKHSA) states that, unless MMR vaccination rates improve, London could be at risk of measles outbreaks, with modelling estimating tens of thousands of cases.


Prof Sir Andrew Pollard, Director of the Oxford Vaccine Group, and Ashall Professor of Infection and Immunity, Pandemic Sciences Institute, University of Oxford, said:

“These new data paint a harrowing picture of the risk to the capital of a measles outbreak because of the large numbers of unvaccinated children and young adults. Measles is very infectious and those at risk are the unvaccinated, including those too young to be vaccinated (<12 months) and children & adults with certain health conditions that weaken their immunity. We must not underestimate the seriousness of this message – if the scenarios modelled in London occur, an outbreak on this scale means that some families will be facing the death of a child.”


Dr Sally Hargreaves, Associate Professor/Reader in Global Health, Institute for Infection and Immunity, St George’s, University of London, said:

“These data highlight that there are pockets of under-immunised communities concentrated in London, which will include migrant communities as one of several groups, who never had a measles vaccine as a child or may only have received one dose.  Some migrant groups we know have low coverage for diseases such as measles, with WHO’s Immunization Agenda placing a renewed focus on the benefits of life-course vaccination, targeting under-immunised communities across the life-course for missed vaccinations, doses, and boosters.  Our data has shown adult and adolescent migrants – alongside other under-immunised communities – in the past have been involved in outbreaks of measles across Europe, due to having missed vaccination for measles in their home countries as children because of war or poorly functioning health systems, their mobility, and then subsequent marginalisation from health and vaccination systems on arrival to Europe/UKThe vaccination of these older groups is an important but poorly evidenced aspect of public health policy in the UK, with the focus mainly on children, and innovative service-delivery approaches are required to increase vaccine coverage.  In the UK, primary care is not currently geared up to engaging and offering catch-up vaccination to migrants and other under-immunised groups who missed measles vaccines as children, and certainly migrant communities may face barriers to registering with primary care where most vaccines are administered.  So these communities will face structural barriers to catch-up vaccination for MMR, but there are also a range of other issues we need to better consider in migrants and ethnic minority groups more broadly – such as lack of trust and confidence in routine vaccines, specific concerns around the MMR vaccine itself and circulating misinformation, lack of tailored health information about the benefits of vaccination across the life-course, alongside challenges faced by healthcare providers in implementing current guidance for catch-up vaccination.

“What the COVID-19 pandemic showed us is that more inclusive and accessible services and policies, including using non-clinical, familiar and community-based settings for vaccine delivery, and culturally tailored and community-led information campaigns and interventions co-produced with the communities themselves, are critical to support vaccination initiatives and drive increases in coverage in under-immunised communities.

“Migrant groups showed lower and slower uptake of COVID-19 vaccines in the UK compared to the host population, due to a range of personal and structural barriers to vaccination systems in the UK; however, the pandemic also led to a great number of innovations in the area of vaccine delivery to these populations that merit further consideration in designing more equitable and inclusive vaccination programmes for routine immunisations such as MMR, which I am sure are being well considered in this new campaign to drive uptake in MMR vaccines in children and adults.  Declining population-level coverage for routine immunisations across the UK, which has accelerated post-pandemic, places these under-immunised populations at even greater risk.”


Dr Peter English, Retired Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice, past Chair of the BMA Public Health Medicine Committee, said:

“Measles is one of the most infectious diseases known.2 It is also a lot more serious than many people realise, with about 1 in 15 cases suffering significant complications.3 Measles can also cause “immune amnesia”, reducing immunity to other infections.4-6

“Measles tends to be more serious if it you catch it after adolescence. In pre-vaccination days, nearly everybody caught it as a child – hardly anybody would reach adolescence or adulthood without becoming immune. But with herd immunity from vaccination, more people will survive to adulthood without measles immunity; and these people will be more susceptible to more serious disease.

“As the introduction of this paper makes clear, in the absence of immunity, each case of measles will typically infect between 10 and 20 people.1 This number, known as R0, is often estimated as being about 15-17.

“If all of the people who would have been infected are immune, then none of them will be infected, so the disease won’t spread. If, on average, less than one person can be infected, we have “population immunity” or “herd immunity”. But if, on average, more than one person is infected by each case, the disease will spread and cause an outbreak. In the absence of control measures, the outbreak will stop when enough people have become immune.

“To ensure It is estimated that over 90% of people need to be immune to ensure herd immunity.

“After a single dose of MMR vaccine, around 90-95% of people will be immune, usually with life-long immunity. After two doses this rises to 99% or more.

“This means that over 90% of the population need to have received two doses of MMR (or been previously infected with measles) for population immunity to be achieved.7

“Even with our excellent data systems, estimating the proportion of the population to have been fully vaccinated is not entirely straightforward, especially in areas (like London) where there is high population turnover.

“This report shows that vaccine uptake rates have dropped. This means that, if measles is introduced to the population (as it inevitably will be at some point), it could be like a spark in a tinderbox, with the disease spreading exponentially as most of the non-immune people exposed to cases become infected, and then spread the disease on to other non-immune people.

“The reports recommendations are very sensible, including:

There is an urgent need to:

  • catch-up children under the age of 5 years nationally
  • catch-up children, teenagers and young people in London
  • coordinate efforts to catch-up teenagers and young people nationally”


  1. Branswell H. Watch: The tricks that make measles so infectious 2019 [updated 14 Feb 2019. Available from: accessed 14 Jul 2022.
  2. Salisbury D, Ramsay M, Noakes K. Chapter 21: Measles. Immunisation against infectious disease. updated 1 July 2013, v2_0 ed. London: HMSO 2013:209-34. Available from:
  3. Hagen A. Measles and Immune Amnesia: American Society for Microbiology; 2019 [updated 18 May 2019. Available from: accessed 14 Jul 2023.
  4. Guglielmi G. Measles erases immune ‘memory’ for other diseases 2019 [updated 31 Oct 2019. 04 Jul]. Available from: accessed 2023 2019.
  5. Morales GB, Muñoz MA. Immune amnesia induced by measles and its effects on concurrent epidemics. J R Soc Interface 2021;18(179):20210153. doi: 10.1098/rsif.2021.0153 [published Online First: 20210616] Available from: accessed 179 18. Available from: accessed 179 18.
  6. English PMB. Should we worry if an increasing proportion of Covid-19 cases are in people who have been vaccinated? 2021 [updated 27 Jun 2021. Available from: accessed 27 Jun 2021.


Dr David Elliman, Consultant in Community Child Health, Great Ormond Street Hospital, said:

“The announcement that London could experience a large outbreak is no surprise.  MMR rates in London have never reached satisfactory levels and have been falling slowly, but steadily, over the last 10 years.  Uptake of all routine vaccines in London has always been lower than most of the rest of the UK, as a whole, and within London are pockets of very low uptake.  It is in these areas that the danger of outbreaks is greatest.  The greatest risk is in teenagers and young adults, but infants under one year of age are also at risk and of course we do not usually offer them MMR.  About 1 in 1000 to 1 in 3000 people who contract measles will die.  If UKHSA projections are correct we could see dozens of deaths in London.

“This assumes that nothing changes.  The intention is to take action to ensure that this does not happen.  All opportunities should be used to check that, especially, but not exclusively, children and young people are fully immunised.

“This, along with the recent concerns about polio and diphtheria, should act as a wake up call about the state of childhood immunisation in general.  It would be much better that everyone is immunised on time, rather than have repeated catch-up programmes.”


Prof Beate Kampmann, Professor of Paediatric Infection & Immunity, London School of Hygiene and Tropical Medicine, said:

“For every 1,000 children who get measles, one or two will die from it.  To avoid deaths, serious cases and a community outbreak, also in the UK, 95% of the population needs to have been vaccinated against this infection, but our current coverage is well below this target.  The measles vaccine is safe and well tolerated.  Each child should have receive their first dose by their first birthday and their second dose by 3.5 years of age to stay fully protected against measles long term and to prevent spread in the community.”



UKHSA press release:

UKHSA risk assessment for measles resurgence in the UK:



Declared interests

Dr Sally Hargreaves: “No conflicts of interest.”

Dr Peter English: is on the editorial board of Vaccines Today: an unpaid, voluntary, position. This comment is made in a personal capacity.

Dr David Elliman: “No conflicts of interest.”

Prof Beate Kampmann: “No COI for a measles vaccine whatsoever.”

For all other experts, no reply to our request for DOIs was received.

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