Since it's halloween weekend, the tv has been filled to overflowing with a variety of horror movies. Zombies continue to be popular. In may, some wag at the CDC put together a short webpage on zombie apocalypse preparedness. It was a lighthearted way to make a serious point about emergency preparedness.
Most of the zombies movies are largely unremarkable but share a common theme - infection. Get bitten by a zombie, turn into a zombie. One film, Syfy's Zombie Apocalypse explicitly invokes the concept of a viral outbreak. Well it got me thinking about the notion of herd immunity. If you set aside the the obvious medical flaws (you get zombie bite and the virus turns you within minutes), the zombie movies are interesting precisely because they point to a situation in which no one has immunity, in which there is no immunity at all. Everyone gets the virus and everyone dies from it.
It got me thinking, though, despite being an otherwise awful movie, 28 Weeks Later portrayed a viable scenario - some people are immune to the zombie virus. This created the promise that someday a vaccine could be found to prevent zombification. Some small portion of the population is genetically immune to HIV; some individuals are not immune to HIV but for some reason their immune systems fight it off. Some individuals and their descendants appear to have some form of natural immunity to the Black Death. I'm sure we could find individuals who have natural resistance to many other diseases (which might be total immunity or a strong immune response that prevents them getting ill or seriously ill).
However, other viral diseases (the flu, small pox, measles, rubella, polio) and bacterial ones (whooping cough) must be prevented or their impact greatly lessened through vaccination. The goal of large scale vaccination programs is to create what is known as community or herd immunity. It's a basic enough concept - enough people are vaccinated against a diseases that even if someone in the community is infected, it limits the ability of the disease to spread.
In recent years, a small group of well meaning but misinformed folks have decided that childhood vaccinations cause autism and have started refusing vaccinations for their children.
The new antivaccine arguments aren't [science based]. Vaccines don't cause autism or brain damage, so when Barbara Loe Fisher or J.B. Handley or Jenny McCarthy or Jim Carrey or Bill Maher argue for safer vaccines, you can't make those vaccines any safer using their definition because vaccines aren't unsafe using their definition. Vaccines don't cause autism, so you can't make them safer by making them not cause autism.
We've done studies that show that the MMR vaccine doesn't cause autism and that thimerosal — the ethyl-mercury preservative in some vaccines — doesn't cause autism. [Antivaccine activists] say that people have to listen to them as parents. Well, that's why we've done these studies and spent tens of millions of dollars to do them: to answer the questions raised by parents. And so, once the question is answered, you could argue reasonably that the parent would say, 'Thank you for paying attention to my question and spending all that money to answer it.' But that's not where they are coming from — they have a belief that is nonfalsifiable. It's a belief system. There is no data that could ever convince them that they are incorrect.
The danger posed by the anti-vaccine movement is simple enough - if herd immunity drops below a certain level, it puts people already at risk, at much greater risk.
Nearly 30% of patients in the current mumps outbreak — which has hit communities in New York state, New Jersey and Quebec — failed to receive one or both recommended shots. And more than 90% of victims in the 2008 measles outbreaks, which sprouted up across the USA, were either unvaccinated or had unclear vaccination records, the CDC says.
A study published Monday in the Archives of Pediatrics & Adolescent Medicine found that unvaccinated children are nine times as likely as others to contract chickenpox — which killed 100 children and hospitalized 10,000 a year before a vaccine became available in 1995. The same authors found that unvaccinated kids are 23 times as likely to develop whooping cough.
So a parent refusing vaccinations for his or her child isn't affecting only his or her child - some individuals are too young to get vaccinations, other individuals are immune compromised and cannot; pregnant women are not supposed to receive certain vaccines. What begins as a single case (the USA Today article cites a family who chose to not vaccinate believing vaccines caused autism and believing that the measles were not as bad for a younger child) can quickly spread among those individuals who for other reasons haven't been vaccinated. Vaccination is powerful simply because it prevents the outbreak:
To illustrate the point, let's return to that bowling alley where people are bowling by themselves. Let's say the guy on the first lane contracts influenza, and he passes it along to the woman on the second lane. If that woman isn't immune to influenza, then the disease will likely continue its path lane by lane until every person in the bowling alley is suffering. But if that woman is immune, then the disease stops with her, because the virus has nowhere else to go (assuming that the guy in our example didn't have contact with anyone else). By her immunity, she protected all the people on subsequent lanes, even if they didn't get a flu shot that year.
Simple enough. There are some challenges - vaccines aren't 100% and there are side effects. The side effects are extremely rare, especially when compared to the real world effects of the diseases they prevent (a polio outbreak for example would easily kill far more people than die from the vaccination and leave other with lifelong disabilities). Your annual flu shot doesn't mean you won't get the flu for sure; if you did get the flu you will experience less severe symptoms. Most anti-vaccination arguments (at least those current today) are extremely weak, based on pseudo-science or just plain bad science. When Jenny McCarthy suddenly started announcing her son "contracted" autism from vaccinations and feeding him a gluten free diet, she was abusing her public status as a celebrity and spreading misinformation. The result has been that some American communities, enough parents are refusing vaccines to threaten herd immunity.
By now, it should be obvious that I'm a great believer in vaccination. So back to the zombie apocalypse question.
If we assume zombies are real, and we assume zombism is spread by a virus, I think we can argue that people must have long ago developed herd immunity. OTOH, given that the whole rotting dead bodies will stop working at some point because there is simply means by which it won't eventually decay to the point that the brain will stop sending signals, the muscles won't be able to receive signals and nerve pathways won't be able to transmit them, I think a zombie outbreak would be surprisingly short lived. Contain the infected through strict quarantine measures, get samples of the virus, develop a vaccine and start performing controlled experiments. Since most viruses require at least a day to incubate before symptoms appear, the usual zombie movie scenario (Oh my god, Tommy got bit! He's turning right before our eyes!) is wildly implausible. Even if we assume that zombie viruses are unusually severe, it would still take time for them to reproduce enough copies of themselves to overwhelm their host. At let's be honest, while zombies make for a sometimes good story, and we love to scare ourselves with them, the usual details of the zombie apocalypse are left vague (our survivors usually emerge from some distant, isolated town or house or a coma) precisely because the details don't hold up under any kind of scrutiny.
I'm not nearly so afraid of the zombie apocalypse as a I am the well meaning but misinformed people who refuse their annual flu shots, who refuse to give their kids the standard childhood vaccinations, who refuse to take seriously the medical science disproving the claims of a link between vaccines and autism.
When I was in grad school, some virus hit the campus and lots of people living in close quarters, lots of people got sick. (I was told that at one point nearly half the students were sick at the same time.) Certain conditions make spreading an illness extremely easy - clue quarters are the biggest among them. As a diversion, it would be interesting to map a cube farm outbreak of a cold or the flu - you'd see the first person arrive with it, then then those around them get sick and then those around the second ring and so on. Your annual flu shot is worth its weight in gold if you consider the time off work it saves you.
A return of the 1918 influenza virus would be devastating enough, we don't need to be afraid of zombies. I recently sent out an email at work with information for my coworkers on flu shots (it's part of my job). I had several people say to me "I'm very healthy I don't need a flu shot." Sounds fine until you consider that exercising every day, eating fruits and veggies don't actually prevent you coming into contact with a virus and while you may be healthy, that doesn't mean you won't get sick. I find myself, regularly, trying to explain to folks that they need to get their flu shots, they need to stay home when they're sick.
We're at a bigger risk from the well meaning but misinformed than we are the mythical and horrifying.
Cross posted at OneUtah.