On Immunity : An Inoculation (9781555973278) (4 page)

Debates over vaccination, then as now, are often cast as debates over the integrity of science, though they could just as easily be understood as conversations about power. The working-class people who resisted Britain’s 1853 provision for free, mandatory vaccination were concerned, in part, with their own freedom. Faced with fines, imprisonment, and the seizure of their property if they did not vaccinate their infants, they sometimes compared their predicament to slavery.

Vaccination, like slavery, raises some pressing questions about one’s rights to one’s own body. But as the historian Nadja Durbach has noted, antivaccinators were often more interested in abolition as a metaphor for individual liberty than they were in the cause as a shared purpose. It was not in the recklessly selfless spirit of John Brown, who was hanged with his sons for their doomed effort to free slaves, that white workers resisted vaccination. “Anti-vaccinators were quick to draw on the political, emotive, or rhetorical value of the slave, or of the colonized African,” Durbach writes of the movement in Britain. “They were quicker still to claim that the suffering of white English citizens took precedence over that of the oppressed elsewhere.” Their primary concern, in other words, was with people like them.

In her history of that movement, Durbach returns often to the idea that vaccine resisters saw their bodies “not as potentially contagious and thus dangerous to the social body, but as highly vulnerable to contamination and violation.” Their bodies were, of course, both contagious and vulnerable. But in a time and place where the bodies of the poor were seen as a liability to public health, as dangerous to others, it fell to the poor to articulate their vulnerability.

If it was meaningful then for the poor to assert that they were not purely dangerous, I suspect it might be just as meaningful now for the rest of us to accept that we are not purely vulnerable. The middle class may be “threatened,” but we are still, just by virtue of having bodies, dangerous. Even the little bodies of children, which our time encourages us to imagine as absolutely vulnerable, are dangerous in their ability to spread disease. Think of the unvaccinated boy in San Diego, for instance, who returned from a trip to Switzerland in 2008 with a case of measles that infected his two siblings, five schoolmates, and four children in his doctor’s waiting room. Three of those children were infants too young to be vaccinated, and one had to be hospitalized.

Unvaccinated children, a 2004 analysis of CDC data reveals, are more likely to be white, to have an older married mother with a college education, and to live in a household with an income of $75,000 or more—like my child. Unvaccinated children also tend to be clustered in the same areas, raising the probability that they will contract a disease that can then be passed, once it is in circulation, to undervaccinated children. Undervaccinated children, meaning children who have received some but not all of their recommended immunizations, are more likely to be black, to have a younger unmarried mother, to have moved across state lines, and to live in poverty.

“Vaccination works,” my father explains, “by enlisting a majority in the protection of a minority.” He means the minority of the population that is particularly vulnerable to a given disease. The elderly, in the case of influenza. Newborns, in the case of pertussis. Pregnant women, in the case of rubella. But when relatively wealthy white women vaccinate our children, we may also be participating in the protection of some poor black children whose single mothers have recently moved and have not, as a product of circumstance rather than choice, fully vaccinated them. This is a radical inversion of the historical application of vaccination, which was once just another form of bodily servitude extracted from the poor for the benefit of the privileged. There is some truth, now, to the idea that public health is not strictly
for
people like me, but it is
through
us, literally through our bodies, that certain public health measures are enacted.

W
E TALKED ABOUT GERMS IN SCHOOL,” my son told me after one of his first days of preschool. The pronoun and the past tense made this a challenging sentence that had taken him several minutes of silence to formulate. He was holding a “germ” constructed of tangled and tortured pipe cleaners that looked not entirely unlike the electron microscope photos in the immunology textbooks I paged through while he was in school. “What did you learn?” I asked. “Germs are really, really tiny and really, really dirty,” he explained with enthusiasm, happy to share his new knowledge. “Yes,” I agreed, “that’s why we have to wash your hands when we get to school in the morning, to wash off the germs so they don’t get on anyone else.” He nodded gravely, “Germs can make you sick. Make you cough.”

The conversation ended there, in part because my two-year-old had, in the span of a few simple sentences, completely articulated my entire knowledge of infectious agents. It was a sobering moment. Sometime after this exchange, I looked up
germ
in a medical dictionary and was reminded that the word is used in two ways. A germ is an organism that causes disease, or it is a part of the body capable of building new tissue. We use the same word for something that brings illness and something that brings growth. The root of the word being, of course,
seed.

We need germs. Without exposure to germs, we now know, a child’s immune system is prone to dysfunction. In 1989, the immunologist David Strachan proposed that having older siblings, belonging to a large family, and living in an environment that was not overly sanitized might help protect children from developing asthma and allergies. This “hygiene hypothesis” suggested that it was possible to be too clean and too free of disease.

As the hygiene hypothesis took hold, scientists searched for one particular childhood disease that might prevent allergies, but this thinking gave way to the understanding that the overall diversity of germs in our environment is probably more important. In 2004, the microbiologist Graham Rook proposed an “old friends” hypothesis, in which he suggested that a healthy immune system is not achieved through childhood diseases, which are relatively new, but through exposure to ancient pathogens that have been with us since our hunter-gatherer days. These “old friends” include parasites and worms as well as the bacteria that colonize our skin, lungs, nose, throat, and gut.

The hygiene hypothesis is still sometimes interpreted as a reason not to prevent infectious disease. “For all we know,” as a friend remarked to me, “diseases like measles may be essential to our health.” But the native peoples of the Americas lived for millennia without measles until it was introduced to this hemisphere relatively recently, with devastating results. And even if we eliminate measles through vaccination, as is theoretically possible, an abundance of germs remain. There are, for instance, about a million different viruses in a teaspoon of seawater. We may not muck around with other organisms as much as we should, but we have no dearth of germs available to us on Earth.

Vaccination of humans has made one single virus extinct—the variola virus that causes smallpox. But novel viruses are constantly inventing themselves, as viruses have a special talent for genetic variation. Of all the varieties of germs, viruses may be the most vexing. They are mysterious creatures, parasitic and vampiric by nature. They are not exactly inanimate, but viruses are not, strictly speaking, alive. They do not eat, do not grow, and generally do not live in the manner that other living things live. Viruses must enter and inhabit a living cell in order to reproduce, or to do much of anything. On their own, they are little more than minuscule bits of inert genetic material, so small that they cannot be seen by an ordinary microscope. Once inside another cell, viruses use that cell’s body to make more of themselves. The metaphor of a factory is often used to describe how viruses work—they enter a cell and force its equipment to produce thousands more viruses. But viruses strike me as more supernatural than industrial—they are zombies, or body snatchers, or vampires.

A virus can, on occasion, infect an organism in a way that ensures the viral DNA will be passed on to that organism’s offspring as part of their genetic code. A rather surprising amount of the human genome is made up of debris from ancient viral infections. Some of that genetic material does nothing, so far as we know, some can trigger cancer under certain conditions, and some has become essential to our survival. The cells that form the outer layer of the placenta for a human fetus bind to each other using a gene that originated, long ago, from a virus. Though many viruses cannot reproduce without us, we ourselves could not reproduce without what we have taken from them.

Our own adaptive immune system, the branch of our immune system that develops long-lasting immunity, is thought to have borrowed its essential technology from the DNA of a virus. Some of our white blood cells combine and recombine their genetic material like random number generators, shuffling their sequences to create an immense variety of cells capable of recognizing an immense variety of pathogens. This technology was viral technology before it was ours. Of humans and viruses, the science writer Carl Zimmer observes, “There is no us and them.”

T
HE NOVEL FLU VIRUS WARNINGS issued by the CDC in my son’s first year seemed to produce, more than anything else, a proliferation of antibacterial soap and hand sanitizer. Sanitizing wipes were stationed by the carts in grocery stores in addition to pumps of sanitizer at every checkout counter. Large pumps of sanitizer appeared at the entrance to security in the airport, in the post office, and at the circulation desk in my library. These sanitizers remained long after the threat of flu had abated.

I was reluctant to be routinely sanitized. My father, whose own hands were often cracked from repeated washing during his rounds in the hospital, had instilled in me a skepticism of anything that promised to kill germs. Not all germs should be put to death, he maintained. Killing germs, rather than washing them away, reminded him of the Crusades, when an abbot who was asked how to tell the faithful from the heretics replied, “Kill them all—God will know his own.”

While hand sanitizers were killing indiscriminately, studies were finding the chemical triclosan in the urine of pregnant women, in the cord blood of newborn babies, and in the breast milk of nursing mothers. Triclosan, an antimicrobial agent used in toothpaste, mouthwash, deodorant, cleaning products, and laundry detergent, among other things, is also the active ingredient in nearly all antibacterial liquid soaps and many hand sanitizers.

What we know about triclosan is that at low concentrations it can prevent both “good” and “bad” microbes from reproducing, and at higher concentrations it can kill them. We know that it is in our wastewater, it is in our streams, and it is in our finished drinking water. It is in wild fish all over the world, it is in earthworms, and it is in the blood of bottlenose dolphins. What we do not know is exactly what this means for our ecosystem.

The upshot of quite a bit of research involving unfortunate mice, rats, and rabbits is that triclosan is probably not very toxic to humans. But the long-term effects of a lifetime of constant exposure are not yet known. Despite the protests of at least one large chemical company, the Food and Drug Administration nominated triclosan for further research at the National Toxicology Program in 2008. Scott Masten, the toxicologist I spoke with there, was rather dispassionate on the subject of triclosan. “I don’t buy antibacterial soap,” he allowed, when pressed, “not because I’m afraid of it, but because it doesn’t have any benefit.” A number of studies have found that washing with antibacterial soaps is actually no more effective at reducing bacteria than washing with regular soap and water. Triclosan is in soaps, Dr. Masten suggested, only because companies have found a market for antibacterial products that promise to kill rather than just clean.

I was interested, I explained to him, in thinking about how the risks posed by triclosan might compare to the risks posed by some of the components of vaccines. Our exposure to triclosan is nearly constant, and it can even be found in the urine of people who do not use any products that contain it. In comparison, our exposure to traces of other chemicals through vaccination is limited to a couple dozen instances. But I did not want to make the mistake of exaggerating the dangers associated with triclosan, I told Dr. Masten, in pursuit of this idea. “Relative risk problems are hard to communicate,” he agreed. The health risks triclosan poses for humans are probably low, but any degree of risk, he reminded me, should be unacceptable in a product that does not do any good.

Fears of vaccines do not seem easily quieted by an abundance of expert risk-benefit analyses assuring us that the good they do is far greater than the harm. Serious side effects from vaccination are rare. But it is difficult to quantify exactly how rare, in part because many of the complications associated with vaccines are also caused by the natural infections those vaccines are designed to prevent. Natural infections of measles, mumps, chicken pox, and influenza can all cause encephalitis, a swelling of the brain. We do not know what the base rate of encephalitis would be in a population with no disease and no vaccination against disease. But we do know that 1 in about every 1,000 cases of measles leads to encephalitis, and that encephalitis has been reported after vaccination in about 1 out of every 3 million doses of the MMR (measles-mumps-rubella) vaccine. This incidence is so rare that researchers have been unable to definitely determine whether or not encephalitis is caused by the vaccine.

A comprehensive report on vaccine “adverse events” was released in 2011 by a committee of eighteen medical experts who reviewed 12,000 studies of vaccination for the Institute of Medicine. They found convincing evidence that the MMR vaccine can, very rarely, cause a condition called measles inclusion body encephalitis in people with compromised immune systems. The MMR can also cause fever-induced seizures that are usually mild and result in no long-term harm. The chicken pox vaccine can cause chicken pox, particularly in people with weakened immune systems. And six different vaccines can cause an anaphylactic allergic reaction in people with severe allergies. The injection of any type of vaccine can produce fainting and muscle pain caused not by the vaccine, but by the act of injection itself.