Where Do They Find These Scary Statistics?
Dr. Gerberding of the CDC
Remember Hannah Poling? The head of the CDC, dressed in a very nice pink suit, appeared on TV and discussed Hannah’s case. In one of her appearances she said something like this: “Vaccines prevent 33,000 deaths a year in the United States.” Just to make sure I had the statement right, I searched for the phrase and found it again, from CNN, this time in print.
Today, through immunizations given in the first two years of life, we can protect children from 16 diseases, preventing 33,000 deaths and 14 million illnesses per year.
A few searches made it clear that this is a very popular statistic. A variety of news stories included the information that vaccines prevent 33,000 deaths a year in the United States. This is an interesting number to anyone who knows a bit about the history of infectious diseases. I decided to dig deeper.
My next find was this chart, which is on a the web-site of an organization called Every Child by Two. The chart provides morbidity (incidence) and mortality (deaths) for each disease. How in the world would someone be able to calculate (for example) the exact number of cases of diphtheria which would occur and the exact number of deaths which would follow? Amazing! There must be some truly extraordinary scientific research underlying these numbers, don’t you think?
I decided that I needed to read the original research. This article is cited in some of the press releases: Historical Comparisons of Morbidity and Mortality for Vaccine-Preventable Diseases in the United States originally published in the Journal of the American Medical Association on November 14, 2007. I got a copy of the full-text article via interlibrary loan. Unfortunately, after I read the article, I discovered that it didn’t actually contain the data to support these numbers. What it does say, on page 2160, is this:
It has been estimated that vaccination with 7 of the 12 routinely recommended childhood vaccines prevents an estimated 33,000 deaths and 14 million cases of disease in every birth cohort, saves $10 billion in direct costs in each birth cohort, and saves society an additional $33 billion in costs that include disability and lost productivity.
The quoted section above had a reference which led me to another journal article. Economic evaluation of the 7-vaccine routine childhood immunization schedule in the United States. Does the data to support the numbers exist, or is it turtles all the way down? One reference, points to the next reference, which points to another reference…but hang in there, I’ll find some data eventually. I promise to track it down!
In the meantime, I want to return to my comment above relating to the history of infectious disease. I recently read this book: The Deadly Truth: A History of Disease in America by Gerald N. Grob
(Cambridge, Mass.: Harvard University Press, 2002). On page 180 Grob states:
…the marked transformation in the pattern of disease that became evident at the turn of the century. Infectious diseases were beginning a dramatic decline as the primary cause of mortality. By 1940 the infectious diseases that had made infancy and childhood the most dangerous stage of life were still prevalent, but they no longer posed a serious threat. As infant and child mortality declined, more Americans reached adulthood and survived to old age.
The history of disease is a fascinating topic. Another excellent source is The Questionable Contribution of Medical Measures to the Decline of Mortality in the United States in the Twentieth Century by John B. McKinlay and Sonia M. McKinlay (Milbank Memorial Fund Quarterly: Health and Society, Summer 1977). Here they are speaking of the decline in the overall age- and sex-adjusted mortality rate since the beginning of this century.
The average annual rate of decline from 1900 until 1950 was .22 per 1,000, after which it became an almost negligible decline of .04 per 1,000 annually. Of the total fall in the standardized death rate between 1900 and 1973, 92.3 percent occurred prior to 1950.
Not a lot of room in these statistics for vaccines to prevent 33,000 deaths each year from infectious diseases in children. This may explain why so many articles about infectious disease talk about outbreaks in the developing world. Are death rates high because living conditions are bad (just as they were in the U.S. before 1900) or because of inadequate vaccination rates? Or both? The core question, and an important one for international health policy, is whether it is possible to defeat infectious disease with medical interventions (such as vaccines) only. Are rising living standards an essential piece of the puzzle?
Over the next few weeks Inside Vaccines will be looking at the “33,000 deaths a year” statistic in detail. Following the references, analyzing the research, and trying to track down the best available data on what vaccination has achieved in the United States. We’ll start with the scariest number. According to the Every Child by Two chart, diphtheria would come back and cause mass illness: 247,212 cases and 24,721 deaths or a 10% death rate. Two-thirds of the projected mortality (33,000 deaths) would be due to this one disease.
What would happen if we stopped vaccinating infants against diphtheria? Stay tuned…