- Measles kills 400 people every day, and has returned to countries where it had been eradicated.
- The MMR vaccine is a safe and effective way of protecting children from measles.
- Studies in countries where MMR was discontinued prove there is no association with autism.
- The best way to counter dangerous misinformation is with good information.
I spent much of the last decade in various African countries. I was often struck by how far mothers would go to get their babies vaccinated. They would spend hours being bounced around in rickety bush taxis on terrible roads. They travelled in the small hours of the morning to be first in line in case the clinics ran out of vaccines, which happens disturbingly often.
These women had lived with infectious disease for as long as they could remember. They may not have known a virus from a bacterium from a protist, but they knew what infections do to children and they weren’t taking any chances with their own.
When I returned to the UK, I found that the vaccination program here has become a victim of its own success. Parents who have never seen the ravages of infectious disease with their own eyes think of it as a myth. Misinformation and conspiracy theories have filled the gap where there was once rational fear. The debate has come to revolve around a few charismatic individuals and is often scientifically illiterate on both sides.
The misinformation seems to be mainly focused on the MMR vaccine, incorporating measles, mumps and rubella. Unsurprisingly, measles has returned to the UK, although it has subsided substantially since 2013. More recently, it has returned to the USA with outbreaks in 27 states, in spite of the fact that the USA was declared measles-free in 2000.
There is no good reason why measles is infecting children in countries where the means to prevent it is available to everyone.
This post is intended to address the myths that I’ve seen circulating. If you prefer simple advocacy, I recommend the illusionist Penn, who tackles the issue with his characteristic straight talking and colourful language:
Doesn’t the MMR vaccine cause autism?
No. The only study that claimed an association was methodologically flawed, and has been withdrawn. The full story has been thoroughly covered elsewhere. I recommend the account of the whole debacle by Ben Goldacre, the arch-enemy of pseudoscience, written when the lead investigator of the study was struck off the British medical register.
In Japan, vaccination with MMR was all but stopped between 1989 and 1992. If MMR really caused autism, fewer children born in those years would have autism than in the year before when they received it. In fact, no difference was observed.
That’s all very well but it’s impossible to prove a negative. Shouldn’t we err on the side of caution and give measles, mumps and rubella separately?
They tried that in Japan when they resumed vaccination in 1993. Autism diagnoses were no different to when children had received MMR.
But if we’re going to err on the side of caution, should we worry that having a television in the house might make a child autistic? Or how about living on the same street as a cat?
There’s as much evidence that televisions and cats cause autism as there is that MMR causes autism. None.
Perhaps the MMR vaccine is safe, but don’t they put mercury in vaccines? Aren’t heavy metals toxic?
Small amounts of thimerosal, a molecule that incorporates mercury, is added to a few vaccines as a preservative. There is no evidence that it caused autism.
In Denmark, thimerosal was removed from vaccines in 1992. If it had caused autism, fewer children born after 1992 would be autistic than before. In fact, the study found the opposite with more children diagnosed with autism after 1992. However, the trend toward higher autism rates started before 1992 so it cannot have anything to do with thimerosal.
While the supposed link between MMR and autism stirred up controversy in the UK and USA, the thimerosal controversy has been largely confined to the USA. The messy history was summarised in an article in the American Journal of Public Health.
There seem to be more and more vaccines given to babies. Won’t this overload their immune systems?
No. Vaccines account for a tiny percentage of what a baby’s immune system is bombarded with.
A baby spends its first year being introduced to the microbes we share our world with. That’s why they get ill so often. They have to come to an accommodation with the bacteria that live in our digestive systems. We can’t digest our food without them, but it’s our immune system’s job to keep them in the gut, where they belong, and to stop them wandering around the rest of our body where they will make us ill. This is a natural process that every newborn mammal endures.
An important element of the immune system is the part that remembers the proteins of microbes it has seen before. Each new species of bacteria the baby encounters introduces it to several thousand new proteins.
Most vaccines are either viruses, which are considerably smaller than bacteria, or single proteins from bacteria. The only exception is the BCG vaccine for tuberculosis which is a small bacterium with around 4,000 proteins, and is not used in every country. Measles, mumps and rubella are all viruses so small that the MMR vaccine has less than 30 proteins.
Isn’t vaccination just a ploy to make money for the pharmaceutical industry?
Please. You try getting a pharmaceutical company to invest in vaccine development. They’re not interested. Why? Because most vaccines are given once in a lifetime, and no public health service will buy them at more than pennies per dose.
Admittedly, there are occasional exceptions but most vaccine development is done in the non-profit sector.
Is measles really that serious? Why take the risk?
Measles killed 400 children every day in 2013, mostly in Africa and South-East Asia. Horrendous as that is, it’s down from over 1500 per day in 2000. In the same period, the percentage of children vaccinated against measles went from 73% to 84%. You don’t have to be an epidemiologist to suspect that might not be a coincidence. This is why African mothers are so keen to get their children vaccinated.
If your child gets measles, there’s only so much a hospital can do about it. Ribavirin is the only drug that targets the virus directly, but it was never intended for use against measles. You wouldn’t want to bet your child’s life on it. Otherwise, the best hospital in the world can only try to keep the child going with hydration, painkillers and vitamin A, and leave their immune system to fight it out with the virus.
Still think skipping the vaccine is worth the risk?
What’s this ‘herd immunity’ I keep hearing about?
If enough people in a population are immune to a virus, the few who are not are protected because they will never meet anyone who can infect them. The ‘herd’ they are part of is immune even if they as an individual are not.
Measles infections rarely last more than a couple of weeks. After that, most peoples’ immune systems will have cleared out the virus and an unfortunate few will be dead. To survive, the virus needs to infect someone else before either of those happen. People who have been infected or vaccinated are no use to it as their immune systems kill it on sight. It has to find someone who is not immune to infect.
For measles, a population becomes immune when around 90% of people are vaccinated. In other words, if more than one in ten people is not immune to measles, there is a strong chance of a measles outbreak that will affect those people.
People can become immune by either surviving an infection with measles or being vaccinated. In countries where there has not been an outbreak for several years, the only way children can become immune is by being vaccinated.
There’s a more complete explanation in Clinical Infectious Diseases.
Is an unvaccinated child a risk to other people?
Yes. A child with measles is infectious before they know they are ill, so they can pass it on to anyone who is not immune. There are several groups of people who are at risk of catching it:
Babies who have yet to be vaccinated
Babies are born with antibodies from their mother, which decline over the first few months as the baby develops its own immunity. The mother’s antibodies would neutralise the vaccine, so MMR is given between nine and twelve months depending on the country. However, there is usually a gap between the point where the baby no longer has enough antibodies to see off the measles virus and being vaccinated. In that time, the baby is vulnerable to measles.
Babies born prematurely have immune systems that are not fully developed, which makes them unable to respond to vaccines and far more likely to die of measles than term babies.
People with immune disorders
There are a number of reasons why someone’s immune system may not function correctly. Some people are unfortunate enough to have genetic disorders that mean they cannot respond to vaccines or protect themselves against infection. Some of the more common types are listed on Wikipedia.
Some cancers are treated with a bone marrow or stem cell transplant. These are effectively immune system transplants, and wipe out the immunity that person had before the transplant. As with most transplants, it takes some time to settle in and the patient must take immunosuppressive drugs for some time. As they lose their own immune system, these people lose any protection they had from vaccines and cannot be vaccinated again until they stop taking immunosuppressants. As well as making vaccines ineffective, the immunosuppressants make those people very vulnerable to infections such as measles.
A child with measles is extremely dangerous to people with any of these conditions.
People who have been vaccinated but are not immune
No vaccine is so good it protects every single person it is given to. Working out how many people are protected is difficult because giving people measles to see if they get ill is unethical. However, studies from outbreaks in the USA and Poland showed 90-95% of people who had been vaccinated were protected, going up to 99-100% if they had been vaccinated a second time. That still leaves a few healthy, vaccinated people vulnerable to measles.
Of course, everyone whose parents decided not to vaccinate them is also vulnerable.
So should parents have their children vaccinated for the sake of other people?
No. They should vaccinate their children for their own sake. MMR protects a child from three nasty viruses and does not cause autism. What more reason is needed?
It’s unfortunate that some of the pro-vaccination rhetoric has gone down this route as undecided parents may see it as pressure to risk their child’s health for the sake of other people. Any parent who feels that is more likely to be put off vaccination than persuaded by it.
The primary benefit is for the child receiving the vaccine. Contributing to herd immunity will benefit others, but that benefit is secondary to the benefit to the child being vaccinated.
If all this is true, parents who don’t vaccinate their children must be terrible people?
Let’s not get carried away. The vast majority of parents want the best for their children, and there’s a lot of misinformation around. Over the last few years, the a few misinformers have been a lot more media-savvy than the rest of us. While the recent outbreaks have made a very convincing argument, it’s not fair to blame people who have fallen for it.
Nobody is persuaded by namecalling, least of all parents who are unsure what is best for their child. What those people need are the facts, which I hope I’ve provided here.