It always strikes me that a strident movement against vaccinations is only possible in a society where vaccine-preventable diseases are mostly invisible.
I want to talk about measles, one of the most contagious viruses known and which, thanks to a very effective vaccine, is on the path to eradication. Australia was officially declared measles-free last year. Also last year, however, Australia saw a huge spike in the number of measles cases, and outbreaks on an increasingly alarming scale are happening now in places where it seemed until recently that measles was all but gone.
Let’s look for a moment at the virus. Measles virus is extremely infectious. It is estimated that 90% of people in close contact with someone with measles will become infected (unless they have immunity from either vaccination or previous infection). On top of this natural infectiousness, measles is spread by droplets which means that every time an infected person sneezes or coughs, they create a little cloud of measles that hangs around ready to infect others. What’s worse is that it can stick around for hours on surfaces like door handles, tables, taps and other places that are likely to be touched by others.
Measles is also not an infection to be taken lightly. Even an ‘average’ case of measles will cause fever, body ache, a full-body rash, runny nose and cough for a number of days. The complications of measles infection can be quite severe – ranging from ear ache, bronchitis and pneumonia through to brain inflammation (encephalitis) in a small number of people. These more severe consequences are not rare – they happen in more than 10% of cases. Measles can, and does, kill too. Most of the measles deaths happen in people who are otherwise not fully healthy – malnutrition and immune suppression make measles much worse.
Controlling a measles outbreak is hard. People generally become infectious a few days before the onset of the characteristic rash and other symptoms which make diagnosis possible. In a world where people travel so much, a vaccine and vigilant surveillance are the best methods for controlling the virus. It’s important to point out here that you need 95% of a population to be immune to measles to prevent its spread, and one of the reasons for the recent outbreaks is that vaccination rates have dropped below that 95% threshold.
So, how good is the vaccine? The measles vaccine, whether given alone or along with mumps and rubella (MMR) or also the chicken-pox virus, varicella (MMRV) is extremely effective and gives a protective immune response in over 95% of recipients. It is a live-attenuated vaccine, meaning that the vaccine contains a weakened form of measles that does not cause disease, but which contains all the parts of the virus that are needed to generate an immune response almost identical to a natural infection. After a single dose of the vaccine, about 90% of people will develop a protective response, and this is increased to about 95% when two doses are given. Most national vaccination schedules (including Australia’s) recommend two doses. Protection from disease is considered to be life-long, and involves both neutralising antibodies which block infection and measles-specific white blood cells which strengthen the response and kill cells which are infected.
The vaccine does have side effects in some recipients. The most common side effect, apart from tenderness at the injection site, is fever which can occur about a week after vaccination. This will occur in about 10% of vaccine recipients. A very small number of people who experience fever can also experience seizures (estimated at 1 in 3000 people, or 0.03%) . It is also possible for people to experience an allergic reaction to some of the vaccine ingredients such as the antibiotic neomycin, although this is vanishingly rare at less than 1 in 1 million vaccine recipients. It is important to remember that these vaccine side effects happen on a much smaller scale than the complications of natural measles infection.
Measles is a serious disease and the vaccine to prevent it is extremely good. It seems a no-brainer that if the vaccine is available, it should be used. Oh, and remember that the link between the MMR vaccine and autism has been well and truly debunked.
Some useful links:
shot of sanity 
Thanks for useful and persuasive facts clearly put – I have always taken for granted the wisdom of vaccinating against disease and now I know why.
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I’ve had some queries to this post, and thought I’d share my responses here. One query was why I’ve said that measles has been eradicated from Australia when there has been an increase in the number of measles cases. Here’s my response:
The current definition for measles elimination is a lack of endemic transmission, meaning that there is no local strain of measles circulating in the community. Elimination also requires a sophisticated and responsive surveillance system to pick up on imported cases, which can obviously still happen when elimination hasn’t happened in all countries around the world. By this definition, Australia still qualifies as measles free – the recent outbreaks have been started by imported cases and have been quite quickly recognised and controlled. Of course, the bigger the non-immune population, the more likely an outbreak is to continue and the more likely endemic transmission is to occur. So the measles free status is not permanent and could be compromised by a bigger outbreak.
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Another query was about the occurrence of complications with measles infection.
The 10% figure quoted in my post is an average for the rate of complications with natural measles infection. Complications are more likely in children under 5 years old and adults, and are affected by other issues like underlying medical conditions and nutritional status. The Centres for Disease Control in the US estimate that ear infections happen in about 10% of cases, and can cause long term hearing loss. Pneumonia is estimated in about 5% of cases, encephelitis in about 0.1%. The main point I was making is that measles is not a nice infection even without complications and that complications are not so uncommon.
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I loved reading a straight forward, unemotional post on this. There’s so much going around and I see the slinging matches between those for and against vaccination.
I read this post with interest. http://www.livingwhole.org/to-the-parent-of-an-immunocompromised-child-who-thinks-my-kid-is-a-threat/ I never know what to believe and what not to believe (not having children it doesn’t really matter for me, I’m just fascinated by the debate. ) I’m curious – do any of the facts in this person’s post stand up?
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