Daniel Patrick Moynihan

High numbers of vaccinated people act like a fire break
that keeps a disease from spreading.

Because anyone can write anything on the web, it can be hard to know what is fact and what is not. I wrote about this in my last blog. And this issue has become alarmingly apparent in a discussion going on in a recent QUEST blog about vaccinations.

In the comments section of this blog, someone writes that herd immunity is a complete myth. This is wrong. Herd immunity is real and actually makes perfect sense.

Obviously for a disease to spread, it has to go from one person to another (either directly or indirectly). A man with measles on a deserted island won’t spread it to anyone because there is no one else who can catch it. Same thing with an infected man in the midst of a group of people immune to the disease.

If we start adding people to the island, then it can spread. And if we put the man with the measles into a group of susceptible people, then it will flare up into a bona fide epidemic (think America when the first Europeans landed).

Now imagine a city where most of the people are immune. If the man with the measles goes there, odds are he won’t meet anyone susceptible. When he gets better, the disease will disappear. This is herd immunity.

Basically the immune people shield the susceptible ones from the disease. They act as sort of a fire break that keeps the epidemic from spreading. Perfectly reasonable idea.

Of course, it is possible that even though this makes sense it doesn’t actually happen in the real world. I decided to look back at the literature and see if there are any real examples of herd immunity out there. There are lots of them. Here are two.

More than a hundred years ago, scientists were noting that not everyone had to be vaccinated against smallpox to stop an epidemic in its tracks*. Scientists also noticed that when they were wiping out smallpox, not everyone needed to be vaccinated to have the disease disappear. In many places, it was enough if 80% of the population could be vaccinated and revaccinated in a 4-5 year period. So smallpox definitely provides evidence for herd immunity.

A common argument against statistics like these is that the decrease in disease came not from vaccines but from better hygiene. To try to counter this argument, I decided to look at mumps.

A mumps vaccine wasn’t really widely available in the U.S. until 1968. Here is a quote from a really thorough review article from 1993 in the journal Epidemiological Review :

"Mumps notifications have now fallen by more than 95 percent since the introduction of vaccination. Given that vaccine uptake has only recently reached that level among school entrants, that uptake among preschoolers is far below that level, and that mumps vaccine efficacy is probably below 90 percent, this decline in incidence is appreciably greater than would be predicted by direct protection alone. Assuming that the decline in reported cases reflects incidence and not a decline in notification efficiency, then this is evidence for indirect protection of susceptibles by herd immunity."

Since mumps vaccinations didn’t start until 1968, it is pretty unlikely that its decrease has been due to better sewers and washing our hands more thoroughly. No, this is a direct result of vaccines and herd immunity.

In fact the whooping cough epidemic can be explained by herd immunity too. It isn’t that not enough people are vaccinated (at least not yet). Instead, it is that the vaccine has worn off for older kids increasing the number of susceptible people. We now have too few people to have a solid fire break and so flare ups of whooping cough are starting to happen.

So despite what you might read on the web (including in the comments section of this blog), herd immunity is real. There is an overwhelming amount of data out there to support the idea that it protects us from the diseases that used to sweep through our population. Herd immunity is a fact and therefore real whether you believe in it or not.

*Farr W. Second annual report of the Registrar-General of Births, Deaths and Marriages of England and Wales, 1840.

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Who would have thought that vaccines would make us smarter?

Vaccines, clean water and freely available medicines may be good for more than your child’s health. They might actually make her smarter.

The idea is that brains take an awful lot of energy to develop and infections sap some of that energy. If someone has a lot of infections, this lost energy will mean less brain development which will mean a lower IQ.

Infections invariably affect the amount of energy a person gets. Think about how rundown you feel when you’re sick.

They can decrease your energy through symptoms like vomiting and diarrhea that affect nutrition absorption. And in every case infections activate the immune system which takes a lot of energy.

The brain is an obvious place from which to get that energy because it is such an energy hog. For example, newborns put 87% of their energy towards brain development and kids and adults use 44% and 25%, respectively.

The connection between lost energy and brain development makes intuitive sense, but where’s the proof? The main evidence for this idea comes from a recent study where the authors try to explain why average IQ varies across the world the way it does. Some countries have higher average IQs than other countries. Same thing with different regions of the world.

Lots of reasons have been put forth to explain these findings but none has really panned out. For example, one idea is that people who settled in cold places needed more brainpower to survive than did people in tropical places. As if finding a cave and lighting a fire is more taxing than surviving lions, leopards, cheetahs and who knows what else. Clearly a bit of Caucasian bias there…

The authors looked at lots of explanations like this and none of them came close to explaining the disparities as well as infection rates. They found that countries with higher chronic infection rates had a lower average IQ.

Not only that, but the authors argue that a continuing decrease in infections explains the Flynn effect. Dr. Flynn noticed that average IQs keep rising after industrialization (although ours may have leveled off in the mid-1990’s). So the idea is that a country’s IQ continues to increase as more and more of its people gain easy access to vaccinations, clean water and medicines.

If it ends up being true that infection rates and IQ are related, it raises some interesting questions for us here in the U.S. Will areas with lower vaccination rates that suffer more disease outbreaks eventually see a decline in IQ? Will the spread of parasites like the West Nile Virus because of global warming lower the national IQ?

Before ending, I should mention that having a higher IQ isn’t all sunshine and roses. Some studies are noting that countries with a higher average IQ also have more cases of allergies and asthma. One idea is that the immune system has to battle something and if there are no infections, it will turn on itself.

So there may be a trade off between IQ and allergies and asthma. If true, we may want to find that sweet spot where people get just enough infections to keep allergies and asthma at bay but maximize IQ. Or we may just want to go for maximal IQ…

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Why aren’t more parents vaccinating their kids?

Whooping cough has reached epidemic proportions in the state of California. And it is hard to know who to be the maddest at.

Should we be mad at the parents who refuse to have their children vaccinated? Or the scientists who have failed to communicate the safety of vaccines to these parents? Or the bacterium itself since it tends to follow a cycle and get worse every 2-5 years? Or the state of California for being too cheap to provide booster shots for 11 and 12 year olds? Or the insurance companies for refusing to adequately reimburse the cost of a vaccine? As you can see, there is plenty of blame to go around.

I can’t do anything about the bacterium itself and little or nothing about the last two. Penny-wise and pound-foolish seems to be the modus operandi of government and the insurance industry. But it seems like other scientists and I should be able to do something about the first two. The question is what…

The facts are out there. Vaccines are very safe and they do not cause autism. All the follow up studies have failed to find a link between autism and vaccines. And the doctor in the U.K. who published the original paper on the subject has had his license taken away because of the unethical way he did the original study.

There is some risk of adverse side effects from a vaccine but they tend to be small. For example, the whooping cough or pertussis vaccine can sometimes lead to severe side effects like shock or brain inflammation. These only happen 1 in 10,000 and less than I in one million respectively. These are much better odds than the 1 in 200 kids who died from whooping cough before the vaccine.

So why aren’t more parents vaccinating their kids? I have always thought that if people have the facts, then they will come to the “right” conclusion. But this is only true if someone can tell good facts from bad. And without training, this can be very difficult which means most folks need to trust the authorities who are reporting the facts. Unfortunately, as our UK doctor and countless others have shown, not all authorities can be trusted.

Chris Mooney is someone who thinks an awful lot about this stuff and in a recent Washington Post op-ed he concluded that, “…based upon my observation, vaccine skepticism seems closely connected to distrust of the pharmaceutical industry and of the federal government's medical research establishment.” What this means is that the facts are out there and the people who don’t vaccinate their kids know about them, they just don’t trust the folks who did the work.

So we don’t necessarily need more facts or getting the facts out there more comprehensively. We need some out-of-the-box thinking to get around this impasse. Here are three possibilities off the top of my head (note that I didn’t even try to come up with a way to gain trust in the pharmaceutical industry):

1) Build up trust in government agencies

2) Circumvent government agencies by creating new scientifically reliable nongovernmental study groups

3) Increase the public’s scientific literacy

Of the three, the best short term solution is probably to create some reliable alternative to government agencies on controversial sorts of issues like vaccinations. Perhaps something like the Bill and Melinda Gates Foundation could fund a group who would try to build consensus on the need for vaccinations and their relative safety compared to the diseases they protect us from. The group would include people opposed to vaccines like Jenny McCarthy, parents whose children have died from whooping cough, scientists with no stake in the discussion, etc.

Maybe these people get together and start the discussion with the fact that, “In 1920 prior to the development of the ‘DPT’ vaccine, one in 200 children died of whooping cough.” Then they propose ways to solve this problem.

Most likely the solution will be vaccines but who knows, maybe people can come up with something better. If vaccines end up as the solution, then the next step is to figure out how to get more buy in for vaccination. Find out why people aren’t getting vaccinated and then build studies or policy suggestions around that.

If people think kids get too many vaccines too close together, then maybe alternative vaccination strategies should be made available. Maybe some people just get vaccines to the real killers and vaccines like chicken pox and maybe even the measles become optional. Would this get more people on board? Would this provide adequate safety for the public?

Also find out what scientific studies this group wants done and by whom to show that vaccines do not cause autism. Then fund those studies and have people that Jenny McCarthy trusts to do the studies. The study would obviously need to be done by someone qualified to conduct such a study but still, get everyone as involved as possible.

Maybe we could push the pharmaceutical industry to create even safer vaccines. Or maybe have nongovernmental organization make the vaccine instead. If we have Pharma do it, then we’ll have to give them incentives. More profits (since profits on vaccines tend to be mighty low) or maybe some protection from lawsuits.

Anyway, the take home message here is that unlike Joe Friday, most people need more than just the facts. They need for the facts to come from someone they trust.

Here's a recent Forum discussion of the whooping cough epidemic.

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You're as likely to be struck by lightning
as to have a severe reaction to a vaccine.

I was reading an article in Time last week about parents not vaccinating their children. The story was about how this phenomenon is becoming more widespread.

These kinds of stories are weird to me because vaccines are pretty safe. The risk of an adverse side effect is incredibly small. For example, the risk for anaphylaxis from the Hepatitis B Virus vaccination is around 1 in 600,000. This is about the same risk as being struck by lightning (1 in 700,000).

Of course, the article wasn't talking about known risks. Instead, it was referring to a hypothesized link between vaccines and autism.

People proposed this link when they noticed that cases of autism and the number of vaccinations were rising at the same time. Of course, just because two things happen to occur at the same time, this does not mean they are causally linked. For example, the increase in global temperature is not related to the decrease in the world's populations of pirates (despite what the Pastafarians say).

So how could an increased number of vaccinations cause an increase in the number of cases of autism? I have seen two ideas put forth. The first is that thimerosal is to blame. The second is that there are so many vaccinations now that we are stressing out the body's immune system. Most likely neither idea is valid.

Thimerosal is a mercury-based preservative that used to be used in vaccines. Even though there haven't been any good studies on the effects of thimerosal on brain development, everyone knows mercury is bad for the brain. So the idea behind thimerosal makes some sense.

Back in 2001, vaccine manufacturers decided to eliminate thimerosal from their vaccines. We would predict, then, that cases of autism should go down significantly if thimerosal was linked to autism. They haven't. In fact, in one California study, cases have continued to climb. So thimerosal is most likely not to blame.

Another point that has been made is that there are so many vaccines now that we are stressing out our bodies' immune systems. Again, this concern is unfounded.

Vaccines are injections of viral proteins. Our bodies see the proteins and raise antibodies to them. Then when a virus invades, we have antibodies that recognize the virus and target it for destruction.

It is the number of viral proteins that matter in terms of taxing the body's immune system and not the number of vaccinations. All of the current vaccines put together do not have as many viral proteins as the old smallpox vaccine (150 vs. 200). So the number of vaccines is unlikely to be the issue.

What all of this means is that vaccines are probably not responsible for the significant increase in the number of cases of autism. What is responsible? No one knows for sure.

It may be that the rise just comes from all of us recognizing the symptoms more. Or it could be due to some cause we don't know about or understand.

What we do know is that vaccines save many lives. I assume no one wants to go back to the early 20th century when polio epidemics swept the country. For example, 2,500 cases of polio ended up at one Los Angeles hospital between May and November of 1934. And in 1952, the U.S. had 21,000 cases of paralytic polio.

We can prevent this sort of thing from happening by making sure everyone is vaccinated. And yet there are people who choose to hide behind the people who take the miniscule risk of getting vaccinated.

Is this a matter of free choice? Should parents be allowed to opt out of vaccinating their children even if it risks society at large?

One idea, I suppose, is to have people who choose not to be vaccinated to sign a waiver saying they accept full responsibility for their actions. In practice this would mean that health insurance and the government would not be responsible for their children's health care bills if they become ill with one of the diseases they refused to be vaccinated against.

And if your infant, grandma, or immuno-suppressed cousin came down with a disease these folks refused to be vaccinated against, then you could sue the un-vaccinated for damages. The common good isn't enough to encourage these folks. Perhaps threats to their pocketbook will be.

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