Experts’ Opinions on the Measles Vaccine Efficacy

By Gift Briton

Experts from various fields have offered their insights and perspectives on the potential link between rising measles cases in the United Kingdom (UK) and the waning of the measles, mumps, and rubella (MMR) vaccine-induced immunity.

This follows a modelling study which examined whether protection against measles from the MMR vaccine decreases over time.

The study published in The Lancet Public Health found that the average waning rate of MMR vaccine is at 0.04 per cent per year.

The Science Media Centre, gathered the opinion of over seven leading experts regarding the study findings.

Prof Alex Richter, representing the British Society for Immunology, emphasized the importance of vaccination coverage and highlighted the challenges of assessing waning immunity in response to the MMR vaccine. He underscored the critical role of maintaining high vaccination rates to prevent measles outbreaks and protect vulnerable populations.

“Our national vaccination programme assumes that two doses of MMR vaccination does provide lifelong immunity and this paper challenges that assumption. However, most measles cases are in the unvaccinated and children under the age of 15. Also, the model assumes that everyone responds equally to the vaccine and we know for example that many immunosuppressed patients may not respond optimally,” Prof Richter narrated.

He added: “Low vaccine uptake likely has a more significant role in increased measles cases, with uptake rates below 90% particularly in younger age groups. However, to determine the true role of waning, immunogenicity studies will be required to assess the short and long-term immune response following vaccination. In the current UK outbreak, one in five children who contract measles are hospitalised. Making sure you and your children are fully up to date with both doses of the MMR vaccine is still the safest and most effective way to protect you and your family from catching measles. If someone is uncertain whether they have been vaccinated, they can check with their GP and request a catch-up vaccine if necessary.”

Dr Louise Dyson, an epidemiology expert from the University of Warwick, noted that while vaccine-induced immunity may decline slightly over time, the overall effectiveness of the vaccine remains significant in reducing the risk of measles transmission.

“The MMR vaccine is highly effective at preventing measles cases, but because measles is very infectious, high levels of vaccination are required to prevent major outbreaks. This research implies that the initial high protection afforded to double-vaccinated individuals wanes slowly over time, with efficacy decreasing by 0.04 percentage points per year. This means that an initial 98% efficacy may wane to 96.8% efficacy 30 years later. These estimates are made by fitting a mathematical model of infection, with and without immune waning, and observing that the model with waning is more consistent with the data. It is always difficult to ensure all the relevant mechanisms are captured well enough to make reliable estimates, but in my opinion, the modelling in this paper is good quality,” she noted.

Prof Sir Roy Anderson from Imperial College London emphasized the need for early childhood vaccinations and raised concerns about the focus on waning immunity in the study compared to broader vaccination coverage issues.

“At present, the key issue is vaccine uptake in the UK (and indeed in many other countries), which is at far too low a level. The second important issue is the age at which children are vaccinated. This needs to be as close to 2 years of age as possible. Loss of vaccine-induced immunity over time is very low in the estimates presented in this paper, which employs models that are relatively simple,” Prof Anderson remarked.

Offering a statistical perspective, Prof Thomas House from the University of Manchester discussed the challenges of interpreting observational data and modelling outcomes in infectious disease studies. He noted the complexity of measles transmission dynamics and the role of vaccination coverage in preventing disease resurgence.

“This study considers the possible impact of waning vaccine immunity to measles in explaining the observation that an increasing proportion of measles cases are vaccinated, although this is still a small minority of cases, and we have to keep in mind that the overwhelming majority of people are vaccinated. As the study press release says, the MMR vaccine remains highly protective against measles for life. As with all studies based on observational data, there is the possibility of confounding, however when a mathematical model is used that accurately captures basic scientific knowledge of the disease system – as has been done here – then that becomes less likely,” Prof House explained.

He added: “It has been known for some time that for a disease as infectious as measles, the period of extremely low infection rates seen after the rollout of MMR – sometimes called the ‘honeymoon period’ – would eventually end due to accumulation of a large enough susceptible population, and indeed we have seen measles re-emerge in the UK although at nothing like its pre-vaccination intensity. This was initially hypothesised as being due to lack of natural immunity with the disease not circulating, but the current study shows that waning vaccine immunity is also likely to play a role, although this study suggests any waning is slow and slight.”

Prof Sir Andrew Pollard from the University of Oxford emphasized the role of health systems in ensuring widespread access to vaccines and promoting community protection against infectious diseases.

“This new publication provides an interesting framework to think about measles transmission dynamics which may be useful for academic discourse. It is a modelling study which by definition uses assumptions which may or may not be correct and cannot capture the complexity of the real world. But in the real world measles cases are on the rise across the globe because children are just not getting jabbed. Most of the problem is the simple inadequacy of health systems, including the NHS, to connect with families, provide knowledgeable advice and ensure easy access to measles and other life-saving vaccines. It is a fact that measles goes away when at least 95% of children are consistently vaccinated in a population and achieving this will stop the ongoing and future outbreaks here in our communities – we must fix this for our children,” Prof Pollard said.

Dr David Elliman, a community paediatrician and consultant, highlighted the importance of reversing the decline in vaccination uptake to prevent measles-related fatalities and protect vulnerable individuals from severe illness.

“Using the authors estimates, this means that at age 45 years, someone who had had 2 doses of MMR in early childhood would have approximately 98.4% protection at 45 years old. That sounds very good to me and obviously, an enormous amount is better than no vaccine. It is vital that we reverse the downward trend in uptake by reassuring parents that the scientific evidence consistently shows that the vaccine is very effective (as shown by this research) and has a good safety record. It would be a tragedy if we see more deaths from this eminently preventable disease,” Dr Elliman said.

Prof Adam Finn from the University of Bristol praised the modelling paper for exploring population immunity changes over time and the implications for measles outbreaks. He emphasized the necessity of maintaining high two-dose MMR coverage to prevent the spread of measles and safeguard public health.

“Although it’s clear that two doses of measles vaccine are highly effective at protecting against measles, the modelling suggests that this protection may reduce very slowly as time passes at least in some people, meaning that they may get measles and pass it on to others if exposed. The implication of this modelling is that it is even more important to achieve and maintain high two-dose coverage with MMR in all areas of the country if we are to stop measles outbreaks from occurring and protect ourselves from the dire consequences of this dangerous but entirely preventable disease,” Prof Finn said.