Thursday, April 2, 2009

Little Ones and Lockjaw

Some concerned family members have asked me to provide evidentiary support for our decision to avoid vaccinations, so far, for our children. Understanding this valid concern, I'm more than willing to provide some. There are many vaccinations that can be discussed, but I'll just focus on tetanus right now because it was mentioned specifically.

I have zero medical training. I'm not responsible for your medical decisions. If you make any judgements based on this post, your lockjaw isn't my fault.

This is hardly a scientific study, but rather my own analysis of other studies. I'm going to show a blatant disregard for things such as significant digits and formal terminology. Where assumptions need to be made, I will tend to grant the benefit of the doubt to support of vaccination. I'm open to corrections, so if you have any please leave a comment or write an e-mail. Finally, I'm going to avoid wasting time defining everything. There is plenty of information available on what tetanus is and what the DPT vaccination is.

Generally, when considering whether to receive medical treatment, an analysis of the benefits and the risks is prudent. If the treatment provides a great benefit while having little risk, it should probably be taken. However, if the benefit does not outweigh the risk associated with the treatment, it should probably not be taken. If the risk and benefit are considered to be equal, the treatment most likely isn't worth the trip to the doctor.

I'm going to roughly evaluate the benefits and risks associated with the DPT vaccine where the benefits apply to tetanus. The DPT vaccine is one of the most well documented. It's difficult to find anything reliable on DTaP. The only thing I read about that had any semblance of a scientific study regarding Pediarix (DTaP/IPV/Hep B, the five-in-one currently used in the U.S.) contained a sampling of only 400, 8 of which had questionable serious adverse events. The sample size is way too small for the probabilities we're considering here, so it's hardly worth mentioning.

If someone wants to argue that the drugs have improved, put forth some serious studies that are readily available to interested parents. In this information age, there's absolutely no excuse for doing otherwise. The onus is not on me to prove how safe a treatment is. If they can't make a decent study readily available to me, they have no business sticking it in my kids.

Before looking at the probabilities of getting tetanus, I would like to establish one fact: the vaccination is not the only thing that prevents tetanus. Sanitation and wound hygeine are also factors. All three of these factors have become more significant over time - the number of vaccinations has increased, sanitation has improved, and wound hygeine has improved.

A Population-Based Serologic Survey of Immunity to Tetanus in the United States by the New England Journal of Medicine found that 69.7% of people at least six years old surveyed from 1988 to 1991 were immune to tetanus. For the sake of simple argument, let's assume that 69.7% of the U.S. population was immune in 1990.

Now, refer to Figure 1 near the bottom of the Tetanus Surveillance report by the Centers for Disease Control. It shows the decline of tetanus cases and tetanus deaths from 1947 to 1997. Tetanus cases began to be recorded in a consistent manner at 1947 when the vaccine was beginning to be used in a widespread manner.

According to the graph, 0.4 of every 100,000 people in the U.S got tetanus in 1947. In 1990, it was 0.025. 0.025 is 6.25% of 0.4. This suggests that the chance of getting tetanus in 1990 was 6.25% of what it was in 1947.

Now, let's assume that 100% of the population was not immune in 1947. This isn't true (though the percentage immune was probably very small), but it doesn't matter for this argument. With that assumption, the percentage of vulnerable people in 1990 was 30.3% of what it was in 1947.

Compared to 1947, the number of non-immune people in 1990 was 30.3% while the number of tetanus cases was 6.25%. In other words, the percentage of tetanus cases decreased faster than tetanus immunity. Yes, these are very rough estimates, but I think they still make one thing clear. Immunity could not have been the only factor in the reduced cases of tetanus.

Now, let's consider the benefits of the tetanus vaccination:

Even though immunity isn't the only factor, let's be conservative and assume that an unvaccinated person today will have the same probability of getting tetanus that people did in 1947 when the vaccination was rare. (I'd go back to a time before the vaccination even existed, but the numbers are less reliable. I want to compare apples to apples as much as possible.) The probability of getting tetanus for that year was .000,4%. Add the fact that the life expectancy of a United States female today is 81 years. This means that, for our argument, the probability of an unvaccinated person getting tetanus today is 1 out of 3,086.

What about death? Let's use the data in the graph again. Consider that, in 1997, about 0.000,016% of the population got tetanus while 0.000,002% died from it. This means that, with 1997 medical care, 1 out of 8 tetanus patients died. If the chance of getting tetanus is 1 in 3,086, then the chance of dying to it with 1997 care is 1 in 24,688. Rough, yes, but good enough for now.

It is not the case that being vaccinated means you will not get tetanus, but let's just assume that it does anyway. This means that the benefit of getting vaccinated is the prevention of a 1 in 3,086 chance of getting tetanus, or the prevention of a 1 in 24,688 chance of death due to tetanus.

On to the risks:

One source of data for the DPT vaccination is a UCLA study published in 1981. According to the National Vaccine Information Center:

"The UCLA/FDA study showed that 1 in 875 DPT shots results in a convulsion or collapse/shock reaction. Two babies in the study died following DPT reaction symptoms, but their deaths were classified as sudden infant death syndrome (SIDS or crib death)."

There were 15,752 DPT immunizations in that study, so if you associate the deaths with the vaccination that's a 1 in 7,876 probability. The cause of those deaths is questionable, so we'll leave them out.

1 in 875 vaccinations result in a serious adverse reaction, but a person's chances of a bad reaction increase if they have more than one shot. According to the typical DPT vaccination schedule, it was administered five times to young children. (It is recommeded that an adult receive a tetanus booster shot every ten years, but this is different from DPT or its variants.) This gives us a 1 in 175 chance of convulsion or collapse/shock in a lifetime.

In 1994, the NVIC reported on a year-long investigation of the Vaccine Adverse Reaction Reporting System (all data available for download at It found that "A total of 54,072 reports of adverse events following vaccination were listed in a 39-month period from July 1990 to November 1993 with 12,504 reports being associated with DPT vaccine, including 471 deaths." ( Keep in mind that these are only the results of the national reporting system. The article goes on to explain, "At the end of February 1994, NVIC/DPT also conducted a survey of 159 doctors' offices in seven states, including Arkansas, California, Georgia, Illinois, Maryland, New York, and Texas. When asked the question, "In case of an adverse event after vaccination, does the doctor report it and, if yes, to whom?" only 28 out of 159, or 18 percent said they make a report to the FDA, CDC or state health department. In New York, only one out of 40 doctors' offices confirmed that they report a death or injury following vaccination."

Ick. Let's be generous and assume that the VAERS database contained 20% of the total number of incidents. That means there were really 62,520 adverse events from DPT, 2,355 of which were deaths. So, how many DPT vaccinations were given during this time period?

I can't seem to find any information that even comes close to estimating the number of actual DPT vaccinations in the U.S. during this period, but I think we can still come up with a very generous estimate. According to the typical DPT vaccination schedule, it was administered five times to young children. I'm going to assume that the CDC's DTaP schedule resembles the old DPT schedule. I'm going to assume that every child born during the time periods that qualify them as being due for a shot during the study's time period lived long enough to get all five shots, and that every single one of them did in fact get all five shots. We can estimate this number of children using the annual birth numbers listed at This estimate is 65,499,055.

Something close to 65,499,055 children were born during five 39-month periods that make them due for DPT shots during the time period analyzed for the NVIC study. I'll assume that 65,499,055 shots actually were given even though it realistically would have been fewer. With 62,520 adverse events and 2,355 deaths, this suggests a 1 in 1,048 chance of adverse event per shot and a 1 in 27,813 chance of death per shot. Multiply those by five shots per person, and you get a 1 in 210 chance of adverse event in a lifetime and a 1 in 5,563 chance of death in a lifetime.

Here's a quick review of my estimates:

If you are unvaccinated:

1:3,086 to get tetanus in lifetime
1:24,688 to die from tetanus in lifetime
1:2 chance your dad's fingers will bleed from too much typing

If you are vaccinated:

1:875 to have convulsion or collapse/shock per shot
1:1,048 to have adverse event per shot
1:27,813 to die per shot
1:175 to have convulsion or collapse/shock in lifetime
1:210 to have adverse event in lifetime
1:5,563 to die in lifetime

So far, it's looking like DPT isn't worth the effort to pull up my child's sleeve. Even if we assume the VAERS database contains every single incident, it still looks bad for DPT. Also, consider that this does not even take into account the tetanus booster everyone is supposed to get every ten years. I don't even need to bother with it.

Based on all of these extremely conservative estimates, if my concern is Tetanus, it would be irresponsible of me to have my children vaccinated.

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