Map of life expectancy at birth from Global Education Project.

Monday, July 11, 2005

By popular demand . . .

The public demands a posting on vaccination. So here goes. The word derives, of course, from the first reasonably scientific demonstration of an effective immunization method. The English physician Edward Jenner heard from a female dairy worker (what was then called a milkmaid) of a popular belief that infection with cowpox -- a disease of cattle that produces mild symptoms in humans -- confers immunity from smallpox. He decided to try it out by first infecting some orphan children with cowpox, and then infecting them with smallpox, to which they proved to be immune. This experiment would be unlikely to receive IRB approval today, but that's water over the dam -- it works.

Although governments throughout Europe and the United States became enthusiastic proponents of vaccination, there was also popular resistance from the very beginning, despite the terrible scourge that smallpox represented. Some people ridiculed the idea; others decried it as unnatural. Anti-vaccination movements did not become highly visible, however, until smallpox had become rare in the U.S. and Europe. Then movements arose that opposed compulsory vaccination as a plot against the working class, or a conspiracy of orthodox physicians to monopolize the profession. In 1905, the U.S. Supreme Court ruled in favor of government power to compel vaccination. Nearly all states, however, still allow a religious exception.

Development of additional true vaccines had to wait until the 20th century, when we began to understand virology and immunology, for it was only a happy accident of nature that a benign disease existed which was closely enough related to smallpox to produce cross-immunity. In the case of other viral diseases, it was necessary to develop synthetic vaccines based on weakened or "killed" viruses, or viral fragments, which could stimulate an immune response without producing disease. The most storied, advance, of course, was the development of polio vaccine, but in the latter half of the 20th Century, effective vaccines were developed for most of the common childhood viral diseases. I can still remember when Rubella, the so-called German Measles, left thousands of children with severe birth defects, including blindness, deafness, and profound mental retardation. That tragedy is now nearly forgotten history.

Yet today, measles and other common, vaccine preventable diseases kill literally thousands of children around the world every day, a fate which is almost unheard of in the wealthy countries. The benefits to individuals and society of universal vaccination seem obvious, impossible to deny. Yet antivaccination campaigns continue. Some people adhere to so-called "alternative" medical theories, and essentially disparage all forms of allopathic medicine. ("Allopathic" is an essentially value-neutral term for the practice that is taught in medical schools and accepted as scientifically valid medicine today; the term's historic origins are interesting but there is no space to go into that here.) Others, however, accept science and argue in scientific terms, but they reach conclusions which are radically dissident.

Like any medical procedure, there is some risk associated with almost every form of vaccination. Vaccinations can, obviously, give a child a sore arm and sometimes a mild disease with fever. More serious complications, particularly neurological side effects, can occur rarely. There have been instances of errors in manufacturing -- as in a case where some children got poliomyletitis from a batch of bad vaccine -- and cases of vaccines that were non-sterile. Indeed, Jenner's cowpox vaccines, maintained by a chain of transmission from human to human, was often contaminated and spread other diseases even as it prevented smallpox. Some vaccines used in the past would not be approved today, and there have been a couple of instances of post-marketing withdrawals, most famously for a vaccine against rotavirus which caused a bizarre, unexpected side effect. (It is very odd indeed that a vaccine could do this, but the side effect was a "telescoping" of a portion of the small intestine, with one segment folding into another.)

Nevertheless, one must compare these risks to the danger of actually getting the diseases vaccines are designed to prevent, and there is simply no contest. On balance, the vaccines in use today are overwhelmingly beneficial to the recipients, and just as much so to the "free riders" who refuse them, but whose children are not exposed to potentially serious illnesses because their schoolmates are immunized. While we usually think of measles, mumps and rubella as just serious nuisances, in fact all three diseases can have serious complications which make the risk of adverse effects from vaccination seem inconsequential by comparison.

There are major problems, however, with the vaccine infrastructure. Vaccines are not very profitable, it turns out, and very few companies are currently in the business. We saw the consequences of this last year when a manufacturer of flu vaccine in Britain had its license suspended and there was a temporary shortage. Fortunately it was not a very bad year for flu and in the end, we found ourselves with surplus vaccine and no epidemiological disaster. The world, however, simply has no means of producing enough vaccine should a highly virulent strain of human influenza appear, as many fear is very likely to happen soon.

So now comes this controversy over the Measles-Mumps-Rubella (MMR) vaccine and autism. In my last posting on this subject I suggested I had not researched this question enough to draw conclusions. I have now remedied that failing and I will write on the subject anon.