Thursday, December 29, 2011

Vaccine Awareness Week: If Vaccines Work...

I haven't had much time lately to generate new posts, but one thing I've noticed lately is that there is a certain anti-vaccine talking point popping up. So I felt it might be a good time to put up an old post again addressing this point.

So, without further ado, here is a post from November 3, 2010 talking about why pro-vaccine people are concerned about those who refuse vaccines.


"If vaccines work, then it shouldn't matter if I don't vaccinate my kid."

That argument, or some variation thereon, is fairly common among anti-vaccine folks and the parents who fall for their propaganda. The thinking is something like this: vaccine proponents claim that vaccines work; if they work, they must be 100% effective; if they are 100% effective, then my kid getting sick won't affect anyone that's been immunized; therefore, why should it matter to anyone else what I choose for my child?

There's a couple problems with this line of reasoning.

First is the strawman argument that vaccines are 100% effective. No one, especially not anyone in the pro-vaccine arena, claims that any vaccine is 100% effective. This fallacious argument also tends to be associated with the black-and-white thinking of the Nirvana fallacy, that if vaccines are not 100% effective, then they are completely worthless, so why bother? Vaccines vary in efficacy. Some are over 90% effective. Many are in the 80%-90% range, while some can be extremely low (e.g., the BCG vaccine against tuberculosis, with an overall efficacy of around 50%, a statistic which has not changed much over the years [PDF]).

Because vaccines are not 100% effective, there is always the possibility that an immunized individual is still susceptible to infection. Chris, a regular commenter at Respectful Insolence and other blogs, wrote up a brief comment that nicely illustrates how herd immunity works. I'll copy it here for ease of reference:

Take 1000 people (ignoring the infants under 2 months who cannot be vaccinated, or babies under a year who can only be partially vaccinated), if 5% refuse vaccines then the numbers are:

950 vaccinated persons (assuming full schedule)
50 unvaccinated persons

The pertussis vaccine is actually only 80% effective at worse, so the numbers are:

760 protected persons
190 vaccinated but vulnerable persons
50 unvaccinated persons

There is an outbreak and it gets spread to 20% of the population, then:

760 protected persons without pertussis

38 vaccinated persons get pertussis
152 vaccinated person who may still get pertussis

10 unvaccinated persons get pertussis
40 unvaccinated persons who may still get pertussis.

In Chris' example, we have a total of 48/1,000 who become infected and 192/1,000 who are still vulnerable to infection. What happens if immunization uptake drops further, to say, 15% refusal?

850 vaccinated persons (assuming full schedule)
150 unvaccinated persons

Continuing with the worst-case 80% efficacy of the pertussis vaccine, the numbers are:

680 protected persons
170 vaccinated but vulnerable persons
150 unvaccinated persons

There is an outbreak and it gets spread to 20% of the population, then:

680 protected persons without pertussis
34 vaccinated persons get pertussis
136 vaccinated person who may still get pertussis

30 unvaccinated persons get pertussis
120 unvaccinated persons who may still get pertussis.

This works out to 64/1,000 who become infected and 256/1,000 who are still vulnerable to infection. That means that increasing total refusal by a mere 10% results in a 33% increase in infection rate and susceptibility.

What does this mean for the anti-vaccine argument? It means that if an unvaccinated child gets infected with one of the vaccine-preventable diseases, they can spread the infection to an immunized child for whom the vaccine, for whatever reason, did not work.

All of this ignores, however, the fact that there are individuals who cannot be immunized at all. The decision not to vaccinate has an effect on those individuals, too, so the "if vaccines work" argument doesn't even apply. Here are a couple of the reasons that an individual may not be immunized:

  • They are too young. Newborn infants may not mount an effective immune response to a vaccine to provide lasting immunity if they are too young; the vaccine may have been studied and found not to be safe to give under a certain age; or, the vaccine may not have been studied in children under a certain age and consequently not approved for use in those ages.
  • They may have an existing medical condition for which there is a contraindication. The CDC has a Guide to Vaccine Contraindications and Precautions (PDF) that lists a wide range of medical reasons not to receive certain vaccines.

Choosing to vaccinate decreases your (or your child's) risk of being infected and passing that infection along to people in those two categories above, not to mention the earlier discussion about individuals for whom the vaccine just didn't work. I'll give a couple examples of why the two bullets above are important to me.

Before I get into that, though, it is important to note that many diseases are contagious before any symptoms appear and remain contagious even after symptoms abate. For example, influenza is contagious for about a day before any signs of infection appear, so it is possible to spread an illness even before you know you have one.

Now, onto examples from real life. Several of my friends and coworkers have recently given birth to beautiful little children. Like most people, I take joy in seeing these new additions to the world, and I really do not want to be responsible for any harm to them. By vaccinating, I reduce my risks of being infected and, therefore, passing the infection along to those infants. If I do not get vaccinated, I am at increased risk of infection, and I may, quite unwittingly, infect the newborn child of my close friend, possibly with rather severe consequences. That is a risk that I am not willing to take. I would rather not gamble with the lives and well-being of my friends' newborn sons and daughters.

I also have a friend who is a transplant recipient due to severe diabetes. Before the transplant, he was pretty much on death's door, requiring frequent visits to the ER for dialysis and resuscitation from heart attacks. He got a new liver and pancreas and the difference was like night and day. Instead of lolling to sleep in the corner, he became vibrant and talkative. He no longer needed regular doses of insulin, and visits to the ER gradually became a memory. The only down side is that he needs to take immunosuppressing drugs to keep his body from rejecting the new organs. This means that he is more prone to infection. Again, I really do not want to be responsible for him developing a disease that could very well put him back in the ER or even kill him. By getting vaccinated, I reduce that risk immensely.

There may be other people with whom I come in contact on a daily basis that may be just like my friend, but I might never know. It isn't exactly like they walk around with a big, neon sign above their heads flashing, "I'm particularly prone to infection and serious complications from disease." I may pass them in the supermarket. Perhaps I brush against them on the bus or subway. Maybe they're next to me in the crowd at a concert or play. It certainly would be unreasonable to expect them to stay sequestered away from all other people and not enjoy life. And so I take the responsibility to do what I can do to help protect them.

Finally, in choosing not to vaccinate your child, you are deliberately withholding beneficial medical treatment and increasing the risk of disease, along with the potential complications for someone other than yourself. Every individual certainly has the right to decide, for themselves, what medical interventions to follow. However, when it comes to deciding for your children, you are not deciding for yourself. Further, your children are not your property to do with as you please. You have a responsibility to ensure their welfare and do what you can to protect them from whatever harms can be prevented. Given that the benefits of vaccinating outweigh the risks, it is irresponsible not to vaccinate your child, barring legitimate medical reasons.

The decision to vaccinate or not vaccinate is not one that only affects the person receiving the immunization. It affects every person with whom they come in contact. (The only exception to that is tetanus, which is not contagious. If you want to risk tetanus, knock yourself out.) Whether you like it or not, you, and your child, are part of the herd, part of the community. Your decision has real effects on the spread of infectious diseases. Think of those around you: your friends, your family, coworkers, people you pass in the store. By vaccinating, you reduce your risk of being infected by any of them, and you likewise reduce the chance of spreading infection to them. By choosing not to vaccinate, you are choosing to risk not only your own health or the health of your child, but the health of everyone with whom they come in contact.

If you're interested in more Vaccine Awareness Week posts, there is are lists at Science-Based Medicine and I Speak of Dreams. You can also find more on Twitter by searching for the #vaxfax hash tag.

5 comments:

  1. Bravo! I really liked how you took my numbers and changed the infection rate.

    I am not an epidemiologist, just someone who used basic statistics when I did work (structural engineer doing vibration analysis). When I watched the movie Contagion I learned that some of the numbers used have specific variable names (it comes out on DVD early January, and my library has lots of copies on order: Bonus!).

    One other thing that is being taken into account is that vaccines do wear off, especially if they are for bacterial infection. Bacterial diseases are notorious for not conferring permanent immunity. Anyone who has had to deal with back to back strep infections should know this (the strep bacteria actually hides from the immune system, which is why there is no vaccine for strep throat or Scarlet Fever). There is also no natural immunity if you survive tetanus (hence the use of the tetanus toxoid, an inactivated toxin, in the vaccine). Even after spending three months coughing due to pertussis, the "natural" immunity can last only about four years:
    Pediatr Infect Dis J. 2005 May;24(5 Suppl):S58-61.
    Duration of immunity against pertussis after natural infection or vaccination.

    And there are some where natural immunity does not even happen. My parents were very surprised when I came down with mumps again!

    It is quite unreasonable to expect a vaccine to provide better immunity than getting the actual disease.

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  2. Good information. Thanks for the link in your comment on Bad Astronomy today.

    However, I want to point out one factor that would affect your numbers. The attack rate is not likely to be the same in the vaccinated and unvaccinated populations. A greater percentage of the unvaccinated will likely get the disease (ie, a higher attack rate), but even so, you can still have a situation where the majority of cases occur among the vaccinated even though they are at lower risk, just due to how the numbers play out.

    Here's an example from the CDC about mumps (see the pink box from Question 1): http://www.cdc.gov/mumps/outbreaks/outbreak-providers-qa.html

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  3. Glad you enjoyed the post and thanks for your comment. Admittedly, it is a very simplified scenario. The higher the immunization rate, the less likely the pathogen will be able to spread. Yet at the same time, because of the sheer numbers involved, there will necessarily be more immunized people than unimmunized people who get infected for the simple fact that there are more of them.

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  4. Todd W, I did enjoy the read. My wife is for immunization and I am against. I wish i could go back to when i was Two months old and shove that needle back into the CDC's eye socket. 3 of the 4 major vaccines darn near KILLED me when i was an infant. I thank God each day for my freedom to choose what is right and wrong. I like to read about the "right and wrong way" to choose in immunization. However I do want to point out one thing that the great Hippocrates said "Let food be thy medicine & let thy medicine be food". If we all lived a perfect life the medical field would not be compaired to as a starbucks (a rip off and Greedy). Ihere is more to it than just Vaccines, we need to study the diets and patterns of life before we point to the vaccines. I am against vaccinations and will not allow my 3 month old son to suffer with our man made, greed enriched toxins in all my research this seems to be a common pattern "Vaccines have never been "proven" to work". Ultimately i choose not to vaccinate; Why, because "it" is my choice. On a serious note Thank you for the read! its no different that any other i have read.

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  5. @TXHippy

    Bear in mind that Hippocrates also believed in the four humours. I mention this because while he did have many good ideas regarding health and medicine, there is a lot that he did not know and a lot of ideas that had no basis in reality. Diet is important for good health, but it will not prevent your getting sick from something like measles or pertussis.

    As to your experience, I'm assuming that your parents told you about it, since you were too young to form any lasting memories. Whatever it was that happened, I'm certain it was quite emotional for your parents and that emotion drove their opinion of vaccines, which they have probably passed along to you. At any rate, there are some questions that come up: which specific vaccines? What was the reaction? What evidence actually points to the vaccines as the cause, rather than some other factor?

    I do not deny that bad reactions can happen following immunization. They are incredibly rare (and if you happen to be one of those rare cases, then that really, really sucks). And I can understand how emotional the issue can be. But it is vitally important to apply reason and logic, to objectively look at the evidence, cutting through those emotions that cloud our judgment. For example, you talk about the "toxins" in vaccines? What toxins? (I'll assume you're not using the term in its strict, scientific sense of "a poisonous substance produced within the cells of living organisms.) Bear in mind that in order to be toxic, a substance needs to be present in large enough amounts to actually cause negative effects. Water, for example, can be toxic at sufficient quantities.

    You also talk about greed. While I readily admit that companies can be greedy (they are, after all, interested in profits and growing their market, as well as funding new products), vaccines really are not huge money-makers for companies. Treating the disease is much more profitable than preventing it.

    Finally, I am very sorry to hear that you will not allow your son to be immunized. You are placing him at far greater risk from disease than you are from any vaccine. Simply because you may have had a bad reaction is no guarantee that he will. It is reason to be cautious and be observant when administering vaccines to him, but it is not a reason to forego vaccines altogether. You might want to read this parent's account of vaccine reaction and why they are still supportive of vaccines.

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