The Misery: Return of Measles
Low vaccination rates in London are an opportunity for the old scourge
“Are you feeling all right?” I asked her.
“I feel all sleepy, ” she said.
In an hour, she was unconscious. In twelve hours she was dead.
The measles had turned into a terrible thing called measles encephalitis and there was nothing the doctors could do to save her.
Roald Dahl
There are certain words what when used by paediatricians have a special meaning. Some are reserved for very specific diseases. The term “miserable”, refers to a state of near inconsolable sadness and distress which is saved for only 2 conditions: Kawasaki disease, and Measles.
Most junior paediatricians will never have seen a case of Measles. Almost no parents of young children will have encountered a case either. This is due to the success of the Measles vaccine (offered routinely in combination with the Mumps and Rubella vaccines as MMR).
In some parts of the country, that may soon change. Rates of vaccination in pockets of London are low enough that significant outbreaks are possible.
It’s time to learn everything you wish you never had to know about Measles.
Measles
Measles is a respiratory infection caused by the Measles virus, a morbillivirus which originated as early as 400BC from the virus that causes the animal disease Rinderpest (ironically, one of only 2 infections we have ever eradicated through vaccination). It was previously commonly known as “First disease”, the first of the 6 common childhood exanthems (infections with a distinct rash). It has also been known as Rubeola and English Measles.
The most common presentation of Measles is a nasty respiratory illness consisting of cough, conjunctivitis and coryza (the 3 C’s), alongside fever and the distinct rash. One of the most distinguishing features of the disease is that the child will be utterly miserable. It’s common for children to have diarrhoea and vomiting. It can also cause the pathognomonic “Koplik spots”, white spots on the inside of the cheeks which only occur in Measles. As they occur prior to the onset of rash and are only present for 2 - 3 days, in practice they are rarely noticed.
One of the remarkable features of Measles is that it is the most infectious pathogen known to humankind. It’s R0 is estimated to be around 15, meaning that in an unvaccinated population one infected individual would on average infect 15 others (compare this to Omicron, which is estimated to have an R0 of up to 8). If an infected person is introduced to a household of 10 people, 9 would be expected to become infected. The reason it is so infectious is that the virus is mainly produced at the top of your trachea, enabling huge amounts of virus to be expelled when breathing, coughing or sneezing. The virus is then able to hang in the air in respiratory aerosols for hours, and remains infectious when inhaled or in contact with respiratory membranes.
The primary danger from Measles comes from its complications, which are common. One in five cases will require hospitalisation. Pneumonia will develop in 1 in 20 children, and this is the most common cause of death. Although it is primarily a respiratory virus, it can also infect the brain. Acute encephalitis (infection and inflammation of the brain itself) will occur in 1 in 1000 cases, often resulting in significant disability such as deafness or brain damage, or death.
It gets even weirder. Measles can also cause blindness, and has been the most common cause of childhood blindness in low income countries. It can do this by either scarring the cornea at the front of the eye, or by damaging the retina (back of the eye) or causing inflammation and swelling of the optic nerve.
Measles can also cause a condition called immune amnesia. Whilst infected, the Measles virus replaces the old immune memory cells with new memory cells specific to Measles. This suddenly leaves you more vulnerable to all the pathogens you had previous acquired immunity against.
And then there is SSPE. Subacute Sclerosing Pan Encephalitis occurs after a child has seemingly recovered from the infection, but in fact the virus has laid dormant. Up to a decade or more later, generalised and progressive inflammation of the brain occurs, leading to untreatable and almost universally fatal neurological degeneration. I will not describe the symptoms here in detail as they are distressing. Whilst overall the rate of the condition is uncommon (1 in 5,000 cases), in unvaccinated infants it may occur as often as 1 in every 600.
There is a strange interaction between Measles and vitamin A. Malnourishment is a clear risk factor for death from Measles, and in particular vitamin A deficiency. Vitamin A supplementation early in the disease course is thought to reduce the risk of blindness and death in children <2 years. Measles itself causes Vitamin A depletion. The mechanisms of this interaction are not well understood.
The impact of Measles was immense. In 1915 in England it was the most common cause of death in children <5 years. The overall mortality rate in healthy populations was more recently estimated to be around 2 per 1000, but this is highly variable and is highest in younger infants. In Samoa in 2019, a state of emergency was declared when 3% of the population were infected due to vaccination rates falling to just over 30%. 83 people died, almost all of them less than 4 years old: a rate of over 14 deaths per 1000 infections. In a famous outbreak in the Faroe Islands in the 1850s, two thirds of the population became ill and up to 2% died. During the same decade in Hawaii, 20% of the whole population was killed by Measles. As recently as 1990 it killed around 800,000 people per year around the world.
A previously monstrous disease causing huge numbers of death and even greater numbers of permanent neurological disability.
What changed?
The Measles Vaccine
One of the most successful medication interventions in history is the vaccine against Measles. It contains a live but severely weakened form of the Measles virus, hence it is not uncommon to develop an extremely mild form of Measles like symptoms around one week after vaccination. The MMR vaccine was developed by Maurice Hilleman (perhaps the most prolific vaccinologist of all time) and licensed in 1971.
It is astonishingly effective. A single dose provides 95% protection against infection. A second dose is recommended due to a small number of people who fail to seroconvert after the first dose, but will after one further vaccination. The immunity is also extremely long lasting, taking more than 200 years for antibody levels to halve. During the first 20 years of the 21st century, Measles deaths around the world fell by three quarters thanks to vaccination. A truly remarkable feat.
Side effects are usually very mild, representing a mild form of the illness from the live viruses used in the vaccine. There is a rare complication known as thrombocytopenia (low platelets) occurring in 1 in 40,000 vaccinations, which itself is a relatively benign condition which self resolved with monitoring alone.
The only controversy surrounding the vaccine stems from fraudulent claims made by the disgraced former doctor Andrew Wakefield. In an infamous, retracted paper published in The Lancet in 1998 (involving unethical research performed on friends of his own children), he claimed a link between the MMR vaccine and autism. No such link has ever actually been observed in any epidemiological research, despite being one of the most extensively studied questions in medical science. Wakefield had himself patented a stand alone Measles vaccine, which he claimed would remove the risk and from which he stood to profit. He also stood to earn up to $43 million a year from a diagnostic test he created for an associated syndrome which he invented and did not exist.
Sadly it is very easy to frighten parents with lies, and this particular lie has continued to have a small but important impact on rates of vaccination ever since. This really matters for Measles. Due to its incredible transmissibility, a very high rate of vaccination in the population is required to keep it out of endemic circulation - over 95%. The infectious disease epidemiologist Adam Kucharski has a excellent blog post covering this issue in more detail.
This leads us to our problem.
Pockets of vulnerability
The pandemic had impacted childhood vaccination rates around the world. This has happened due to lack of access during periods of lockdown or reduced health service availability, diversion of resources towards Covid-19 vaccination, and increases in vaccine hesitancy associated with the deployment of the Covid-19 vaccine.
There are particular populations who have historically had lower rates of vaccination, due to structural difficulties in accessing health services. Now in London, some of these communities have worryingly low vaccination related for MMR - below 70%. Rates of Measles are also increasing in London, with 128 cases in 2023 so far compared to only 54 in 2022. Modelling from the UKHSA has estimated the possible impact of Measles among these vulnerable pockets where vaccination rates are lower and large outbreaks could result. They estimate anywhere up to 160,000 thousand cases could occur, leading to significant morbidity, disability and death. It is a tragedy that this would occur when almost every single case could potentially be avoided by vaccination. A particularly vulnerable group are older adolescents and young adults, who missed their childhood MMR due to the fear caused by Wakefield’s fraudulent publication.
Public health outreach programs are needed to offer and promote catch up vaccinations in these communities to protect these vulnerable children.
Summary
Measles is the most infectious virus known to humankind, and has very high rates of complications in young children. It was one of the most common causes of childhood death and disability prior to the introduction of vaccination. The Measles vaccine (as part of MMR) is one of the most effective vaccines ever produced, providing near complete, lifelong protection from infection. Due to previous fraudulent publications, and the impact of the Covid-19 pandemic, rates of vaccination are now low enough in some population in London that large outbreaks could occur. This is entirely preventable by increasing rates of vaccination.
The quote at the start of the piece is from Roald Dahl, lamenting the death of his 7 year old daughter Olivia from Measles, prior to the availability of the vaccine.
…there is today something that parents can do to make sure that this sort of tragedy does not happen to a child of theirs. They can insist that their child is immunized against measles. I was unable to do that for Olivia in 1962 because in those days a reliable measles vaccine had not been discovered.
Today a good and safe vaccine is available to every family and all you have to do is to ask your doctor to administer it.
It really annoys me when ignorant people try to link vaccines to autism. I'm autistic, and due to my age, I didn't have any childhood vaccinations. My kids are both autistic too, because there is a genetic factor with autism which was discovered several years ago but, research being what it is, it's still in early stages.
My boys had all their childhood shots - my parents lost friends to measles as children. I'd had 4 miscarriages before my boys arrived, they were so precious. However I'm more circumspect about what they have now, so it's a no to the flu shot etc.