Friday, June 20, 2014

Pre-Vaccine Declines in Measles Mortality

On Monday, I discussed "pox parties" and "measles teas", social gatherings where parents get their unvaccinated, nonimmune children together with another kid who has a disease, the purpose being to intentionally infect their kids and make them sick. It is a practice that, for at least a hundred years, has been decried by the scientific and medical community as a wretched idea, with one author describing them as "orgies of death". Indeed, in my opinion, these parties are nothing more than child abuse.

While vaccine preventable diseases are not the killers they once were, as I mentioned in passing in that post, they are still quite dangerous; diseases like diphtheria and measles should be avoided and prevented whenever possible. Anti-vaccine activists seem quite enamored with pre-vaccine mortality data. They like to point to the declining death rates from diseases and declare that vaccines not only did not save us from those diseases, but that we didn't need vaccines anyway. There are a couple of things wrong with this way of thinking. First off, it erroneously focuses on disease mortality and pretends that deaths and incidence are somehow the same thing. The implication is that the incidence, that is, the number of cases, was declining before the vaccines. Or they just come right out and say that death rate and incidence are the same:
Measles cases in all developed countries became much milder than in developing countries mainly due to improved diet. Is it logical that deaths associated with measles declined greatly without any corresponding decline in incidence?
That is, quite simply, false, not to mention sloppy thinking. Second, it ignores the non-fatal, but still quite serious, complications of diseases, such as severe dehydration, pneumonia, deafness, blindness, encephalopathy and permanent mental impairment, among others. And, yes, these diseases can still kill, even in developed nations with good healthcare like the United States.

I will readily admit, the measles vaccine did not contribute to the decline in deaths seen before the vaccine was licensed. (Duh!) But while anti-vaccine activists assert that the disease just got less dangerous on its own, they're wrong. Here's why.

As with many of the claims spewed into being by vocal vaccine deniers, I decided to delve into the literature to see what I could find. It's a practice that, if they adopted it themselves, could save them a lot of time and embarrassment. The graph they like to trot out in support of this particular claim shows measles deaths from 1900 through the 1980s:

U.S. measles mortality per 100,000 population, 1900-1984
Looking at this graph, it's pretty clear that death from measles declined considerably before the introduction of the vaccine. Death rate remained fairly steady through the first 18 or so years, then started to drop until about the 1940s, where it leveled off quite a bit. After introduction of the vaccine, it dropped to almost nothing. A similar graph, though looking at a smaller range and using a logarithmic scale, shows a similar, though more even and gradual, drop in deaths:

U.S. measles cases and deaths per 100,000 population, 1912-1974 (logarithmic scale)
Source: Barkin RM (1975). Measles mortality:a retrospective look at the vaccine era. Am J Epidemiol.
The second graph also shows that although deaths from measles declined, the incidence, that is, the number of cases, remained quite steady until about 1963, when the first measles vaccine was approved. One other thing to note in this graph. Sometimes, anti-vaccine folks will simply draw a straight line following the general slope of the data and extrapolate that by 2010, measles would not cause any deaths and would be gone on its own. But that ignores changes in medical care that occurred over that span of time, as well as ignoring changes in the slope itself. We see, for instance, that there's a gradual decline until the early 1920s, then a slightly steeper slope until the late 1940s, with a leveling off in the 1950s. A perfectly straight line just doesn't fit, at least if one is being honest. We see a precipitous drop in the number of cases around 1963. Notice, also that while death rates had been declining, those also dropped about ten-fold in the space of a few years. Compare that to the pre-vaccine era, where it took decades for an equally great drop in death rates (e.g., 1918-1943 and 1943-1967). That impact is something that you don't see in the graph favored by anti-vaccine folks.

For this post, though, I want to focus on that gradual pre-vaccine decline in mortality. What should be clear is that although the incidence in diseases did not change before the introduction of the vaccine, mortality was decreasing. Was the virus changing; did it becom less virulent? Did the virus stay the same while we just got better at keeping patients alive? Ask an anti-vaccine advocate what happened, and you're likely to get an answer that the virus itself was getting less deadly (i.e., less virulent) or that improved diet, sanitation and hygiene are what did it. Or some combination of those two. Period. End of story. The scientific literature paints a slightly different picture (surprise, surprise).

The early part of the 20th century saw a lot of significant changes affecting the way we live. Diets progressively improved, sanitation got better and overcrowding declined. These did have a big impact on overall health of the population. Malnutrition contributes to more severe courses of disease and increased mortality. Poor sanitation can increase the incidence of diseases spread via contaminated food or water, though not respiratory diseases like measles. And overcrowding creates conditions where there are many opportunities for a disease to find new hosts, spreading rapidly. Of course improvements in these areas would also contribute to improved outcomes following infection with a disease. But they only account for a portion of the measles mortality picture.

In the early 1900s and continuing through the middle part of the century, most measles deaths were not from the virus itself. Rather, secondary bacterial infections contributed significantly to the high mortality rate following measles, the most common of which is bacterial pneumonia (Babbott & Gordon, 1954). Common opportunistic bacteria to cause complications were streptococcus, pneumococcus and H. influenzae. In the first decade, there were no antibiotics that could treat these secondary infections, and for a number of years afterward, the antibiotic arsenal was limited. The only control measures available were imperfect attempts at quarantine to limit outbreaks. But given measles' ability to spread before symptoms appear, such attempts were more or less futile (Curtis, 1916). Outbreaks simply had to run their course, and families had to hope that their children would survive. The advent of antibiotics, however, gave a new tool to drastically reduce the impact of secondary infections. Drugs to wipe out these pathogenic bacteria were a boon to doctors and their patients, allowing for a significant cause of death following measles to be virtually eliminated.

Another medical intervention which had a big impact on measles mortality was the use of gamma globulin. There were essentially two ways to use gamma globulin: temporary prevention of disease or modification of disease. In both cases, it was given to those who had been exposed to the virus. For prevention, it had to be given within 6 days of exposure (Janeway, 1945). If a sufficient dose was given soon enough, there was a decent chance of preventing the infection from taking hold. The good side is, the child would not get sick and be at risk for complications, like death. The bad side is that the immunity would only be short-lived; eventually, if re-exposed, the child could be infected again. For that reason, the dominant recommendation for gamma globulin was to use it to modify, rather than prevent, the illness. A smaller dose or one given too late for prevention could make the course of measles milder, while also allowing the patient to develop immunity to the virus. Although this could make the incubation period for the virus longer, the recognizable disease would have a shorter duration and much lower risk of complications. (Janeway, 1945). Other serum products, predating gamma globulin use, also had potential to prevent or modify the disease, though not as safely or effectively as gamma globulin (Babbott & Gordon, 1954). Modified disease, however, was still transmissible. These products, though, were not particularly cheap and did carry a risk of some serious side effects. They had to be used judiciously.

Another aspect that likely contributed to the declining death rates from measles were fertility and family size. From the beginning of the 20th century until the mid-1930s, birth rates steadily declined, leading to fewer children per family (Guyer, Freedman, Strobino & Sondik, 2000). This pushed the median age of infection off until children were slightly older. The shift in age of ingection was hypothesized to have played a significant role in the reduction in infectious disease mortality (Reves, 1985), considering how dangerous measles was for those under 3 years of age (Henry, 1921).

A final factor that likely played a large role in the reduction of deaths from measles, particularly in the first few decades of the 1900s, was the establishment of local health departments and improved access to health care (Guyer et al., 2000). Local health departments could help to educate the populace about diseases and how to minimize the risks of exposure and infection. Over this period, as well, improvements in neonatal and postneonatal care reduced mortality and improved the overall health of infants. Increased access to health care for infants and young children could address conditions that might have otherwise contributed to complications of measles, just as measles could negatively affect the course of other diseases, such as tuberculosis (Babbott & Gordon, 1954).

A couple things that did not change were the virulence of the virus (Babbott & Gordon, 1954), nor the risk of encephalitis, at about 1 in 1,000 cases (Babbott & Gordon, 1954; Perry & Halsey, 2004; Griffin, 2010). And while the risk of death has dropped significantly, it is still somewhere around 1 in 1,000 cases to 1 in 3,000 cases here in the U.S.

The history of measles mortality in the pre-vaccine era is rather complex; it's not simply a matter of better food and sanitation. While improvements in overall nutrition, sanitation and housing/overcrowding did contribute to improved health outcomes early in the 20th century, they are not the only factors that played a role in the declining mortality following measles infection. Advances in medicine and healthcare, the use of gamma globulin and other serum products, the advent of antibiotics, improved education and decreases in family size also helped to make measles a less fatal disease. However, it is difficult to quantify the exact degree each of these factors played, since we are dealing with historical data of oftentimes varying quality. I would argue, though, that if I had to choose one intervention that has had the most impact on measles deaths throughout history, I would pick vaccination. After all, if you never get infected with it, you can't die from it.
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References and Additional Reading:

16 comments:

  1. I agree, especially with your last sentence. When you look at the havoc that measles still causes in places where vaccination does not occur (and the 100,000+ deaths yearly that measles still causes), why would anyone want to stop vaccinating against this awful infection?

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  2. The fact is clear that despite your arguments, mortality had already declined by 92% last century before medical care really kicked off. Chart of it is on page 6 of this article here:

    http://www.columbia.edu/itc/hs/pubhealth/rosner/g8965/client_edit/readings/week_2/mckinlay.pdf

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    1. What year did medical care get kicked off? Was it before or after 1950? Give a specific year and what prompted the great improvement outpacing all others. If you say after 1950, I have a list of history books for you to read. You can start with this 1920s classic.

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  3. 108 measles death due to vaccines in the US in the last 10 years and 2,000 disabilities. Put that in your pipe and smoke it. Check out the VAERS stats on this. Also, the Mickey Mouse Measles 'outbreak' supposedly caused by Phillipinos while Phillipines says they eradicated the disease years ago. The MMR vaccine is a live virus and is leading to the spread of the disease even though you don't want to admit it. Vaccines also contribute to a decrease in natural immunity leading to the increase in things like childhood cancer, obesity, IQ reduction, etc.CDC admits no study comparing non-vaccinated to vaccinated populations! They don't want one! If the vaccine is so good, what are the vaccinated people afraid of? Why do vaccinated people keep getting the very disease they were vaccinated against? Get rid of your herd mentality and open up to the truth and stop drinking the vaccine Kool Aid! www.wakeupelbert.com

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    1. Hi, Dana. First off, would you mind providing a citation for your 108 figure. If VAERS is your only source, then I humbly suggest you learn a bit more about what VAERS does and doesn't say.

      The Philippines is still recovering from a major outbreak in 2012. They still have endemic transmission and have not eliminated the disease. Furthermore, the current measles outbreak in the U.S. stemming from Disneyland is not the vaccine strain. The vaccine uses the A genotype. The current outbreak is the B3 genotype. And before you claim that means the vaccine is ineffective, there is only one known serotype of virus, meaning that the vaccine protects against all of the genotypes.

      As with your death figure, do you have a citation for your claim about decreased natural immunity and it leading to increased cancer, obesity, IQ reduction, etc.?

      Regarding your, "if vaccines work" comment, I suggest you read this. Keep in mind that hundreds, if not thousands, of people were exposed at Disney. If the vaccine did not work, then we would be seeing many, many more cases of vaccinated individuals getting sick, and the outbreak would be significantly larger.

      If you have actual scientific evidence to back up your claims, by all means present it. If it is valid, I will change my position.

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  4. fine, vaccines reduced incidence rate, but deaths were still very low when it was reduced. I think compared to the number of people who die in other ways (homicide for example, or car accidents) and the alleged negative effects of vaccines, it is not a number to get hugely alarmed about. I speculate with today's better health care deaths would be even lower.

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    1. A couple things to keep in mind. I just recently took a look at the National Vital Statistics System to search for deaths related to measles. From 2000 to 2013, there were 10 measles-related deaths in the U.S. reported in the NVSS database. Now, I was only able to confirm 2 of those deaths from other sources. In that same period, there were 1,243 cases of measles. That gives us, on the low end, a death rate of 1.6 deaths per 1,000 cases of measles. That number is only for deaths and does not include other serious but non-fatal sequelae, such as brain damage, deafness, pneumonia, or hospitalization for other consequences of the disease. If you can show that the vaccines have similarly high rates of death and serious injury, then perhaps your argument might have some weight. So that's the first thing.

      Second, just because people die in other ways doesn't mean that we cannot also prevent causes of death where we can. Just because a lot of people may die or be injured in car accidents doesn't mean that we should abandon the effort to prevent measles.

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  7. I don't know how old you are but I am sorry to inform you that prior to the mid Seventies at least and perhaps in some countries the late Seventies, doctors fully supported 'parties' to spread infection for these minor childhood diseases on the basis that it was better to get it young and get lifelong immunity since all were more serious in adults.

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    1. For which diseases and why? Provide the PubMed indexed article from the 1960s and 1970s that this was health policy in any country.

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    2. Hi, Roslyn, Ross,

      Here's another post you might be interested in reading: http://www.harpocratesspeaks.com/2014/06/orgies-of-death-dangerous-tradition-of.html

      It includes some quotes from the early half of the 1900s, in particular, one from a doctor who described pox parties as "orgies of death".

      While some doctors did recommend exposing kids to those who had chicken pox so they got it sooner rather than later, the best thing was to avoid it completely if possible, since chicken pox is not without serious risk. I'd also recommend reading the Pink Book chapter on Varicella, as well, to get a better idea of the complications of the disease.

      As for measles, the topic of this post, I'm not aware of any doctors recommending "measles teas", but I am aware of doctors who had argued against them. Measles had a greater risk of serious complications than chicken pox and is much more contagious. Now, even if some physicians did recommend exposure through "parties", that doesn't mean that it was a good idea. In fact, any doctors who did so were seriously misguided, particularly since in the late 1970s there was an effective vaccine available.

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  8. Is not the real question for your graph, why, after the introduction of a measles vaccine in 1963, did it rise again dramatically, 68-72?

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    1. Because the vaccine coverage was very spotty, and 1970 was an expected epidemic year.

      What was surprising was that the drop of measles incidence with only certain kids vaccinated (mostly from well employed families with health insurance) was much greater than expected. See:
      Mass measles immunization in Los Angeles County
      and
      Measles epidemiology and vaccine use in Los Angeles County, 1963 and 1966

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    2. @Roslyn Ross

      There are several factors at play:

      1) There were two measles vaccines introduced in 1963: an inactivated vaccine and a live attenuated vaccine (several different companies produced these). The inactivated vaccines was not very effective and was withdrawn in 1967, so those who received the inactivated vaccine had a greater risk of vaccine failure.
      2) When first introduced, the recommended age was 9 months. It wasn't until 1965 that the recommended age was changed to 12 months. The vaccine, as we found out through many studies, is less effective if given before 12 months. Again, those who were immunized early were at greater risk of vaccine failure.
      3) It wasn't until 1966 that a nationwide effort was made to eliminate measles, so, as Chris pointed out, vaccine uptake was spotty until several years after that goal was set.
      4) It wasn't until 1989 that a second dose of measles vaccine was recommended. Like age at first immunization, several studies led to the discovery that a single-dose schedule had a higher rate of vaccine failure than a two-dose schedule.

      Those are vaccine-related factors that played a role in that small (in the grand scale) uptick in the late 60s/early 70s. There may also have been other factors (e.g., socioeconomic, demographic) that played a role, too.

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  9. "I don't know how old you are but I am sorry to inform you that prior to the mid Seventies at least and perhaps in some countries the late Seventies, doctors fully supported 'parties' "

    I wish you could provide some corroboration for this statement. All of the childhood diseases we suffered in the 1950's and 1960's we (my six brothers and sisters and I) managed to catch without the help of 'parties.' With measles in particular, no such events would have been necessary, as one infected child in a school would have passed the disease on to 80% of the other children in his or her classroom.

    Do you have documentation supporting the existence of these parties and the medical support for them?

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