The History of Vaccines and the Importance of Vaccine Mandates
Part 4: Vaccine Inequality and the Case of Polio
Dr. Thomas Francis Jr. stepped to the podium inside Rackham Auditorium at the University of Michigan on April 12, 1955. The world watched anticipating the results of a massive polio vaccine trial in which over one-million children had been given a new vaccine. Although polio had been first identified by Michael Underwood in the late 1789, it likely existed for centuries. Even when Underwood identified the disease, it wasn’t widely noticed. Polio didn’t fully step to public consciousness until the 20th Century when 27,000 people were infected and 2,000 people died in a 1916 New York City outbreak that spread across the northeastern United States. At its height soon after, polio killed or paralyzed nearly half a million people across the world every year.
With the words “safe, effective, and potent” Dr. Francis announced the results of a long search for an effective vaccine pioneered by his former student, Jonas Salk. Salk’s vaccine was 80 to 90 percent effective in preventing paralytic polio. Francis’ words and the results of the trial gave hope to many that the suffering from polio would soon end entirely. (A short documentary video about polio and the race to find a vaccine with clips of Dr. Francis’ announcement can be found here.)
The race to find this vaccine became so dire in part because of the cruel manner in which polio affected victims. Out of every 200 symptomatic infections, one would be stricken with severe disease and paralysis. With cruelty many of these cases seemingly appeared at random without a known source of the infection. In part this was because of a feature that polio shares with our current nemesis Covid-19 - asymptomatic transmission. Only about 25 percent of polio infections resulted in symptoms, 75 percent remained entirely free from any indication of a polio infection. Further many of the people who were symptomatic suffered only minor ailments like headaches, fatigue, and fever. Yet, pictures of paralyzed children made the disease more palpable for the masses who feared that their own children and those of their neighbors, friends and relatives would suffer the same fate. For those who suffered most severely it was a sinister disease indeed. With the words of Dr. Francis many in the world relaxed. We now had an effective and safe tool to fight polio. But sometimes the existence of a tool is not enough.
The early returns to the Salk vaccine provided hope. In just two years, U.S. cases dropped from 58,000 to 5,600 (1957). Then the decrease in cases stalled before a new surge began, particularly in impoverished urban neighborhoods. As historian Frank Snowden writes, “the incidence of polio among African Americans in inner cities and among Native Americans on reservations was four to six times the national average.” One can see this clearly from a study by Tom Chin and William Marine of a 1959 outbreak in Kansas City. While pre-vaccine outbreaks were more or less evenly spread across the population, post vaccine outbreaks were located in Black inner city neighborhoods. As they write, the case rate of polio among the Black population in “Des Moines [IA] was 20 times higher than for upper [class] whites, and in Kansas City it was 32 times higher.” The reason was simple: we failed to vaccinate this marginalized population. The rate of vaccination was 1/2 the rate of the most wealthy in these cities. In the same time period outbreaks like this were occurring in Chicago, Des Moines, Detroit, Washington D.C., and other cities across the country.
From Chin and Marine Public Health Reports 1961.
In part, this was simple social neglect of a group traditionally marginalized by the US healthcare system. In Mobile, Alabama Black children were bussed to white schools to receive the vaccine. They met a nurse on the lawn of the school and were not allowed inside, even to use the bathroom. Additionally, polio often was described (incorrectly) as a “white” disease. In 1951, a physician speaking at the March of Dimes described a recent outbreak among the Black population as “unusual” because “usually polio strikes blonde, blue-eyed persons as a far greater rate” than Black people. The racism was evident. Yet there was another reason that the Black population continued to be struck by polio that involves the distribution of vaccines.
For a moment, imagine a lightning strike that begins a forest fire. First one tree catches fire, then a neighboring tree. Then another and another until it runs out of wood to burn. The US forest service tries to help control forest fires before they start by clearing old brush and thinning the number trees in areas at greatest risk of a fire.
Forest 1.
Imagine that the original forest looks like the one above. Now imagine that one-half of the trees are cleared from the forest resulting in this second forest.
Forest 2.
In this depiction one-half of the trees in the forest have been removed. This helps to contain a fire because there are fewer trees to be struck by lightning. More importantly, it is much more difficult for a fire to spread widely if one starts because any tree that burns has few neighbors to which the fire may spread. Consider another possibility though. Suppose that we remove one-half of the trees but this time we leave a large block of the forest untouched. Here is one possibility.
Forest 3.
Forest 3, like forest 2 has the same number of trees (each has ½ of forest 1). But now, the portion of the forest that remains has nearly the same risk as it did in the original forest. It is marginally protected because there are fewer trees to start a fire, but once a fire starts among the remaining group of trees, the fire will burn almost exactly as it would prior to removing one-half of the trees.
It is relatively easy to show that the same thing happens with vaccinations. If you leave a group unvaccinated, where many of the members of the group interact with each other, you have done very little to protect this group from infection. (Myong-Hun Chang and I have a series of academic papers showing this in computational simulations and also mathematically.) Even worse, because vaccines are not 100% effective, you also leave the vaccinated more at risk because a large outbreak is more likely.
This was happening with the distribution of polio vaccines in the late 1950s. Large portions of the population were untouched by the vaccine. The people in these groups were susceptible themselves, but they were living near other people who were susceptible too. Once a chance infection occurred in their neighborhood, the outbreak was little different than if the vaccine had never been invented.
It wasn’t until Albert Sabin invented a new oral vaccine using weakened live virus in the 1960s that polio was brought under control in the United States. How did they do this? Sabin’s vaccine was much easier to distribute. It was given orally with a small drop of vaccine on a sugar cube. This simple method of providing this vaccine made it easy to distribute in schools and at community fairs. No longer did inner city children need to be bussed to suburban white schools to receive the vaccine from physicians and nurses with special training. The vaccine was brought to the people. They received it in their home communities and in their schools. Polio was conquered as much by ensuring adequate distribution to the entire population as by the invention of the vaccine. Widespread and equitable distribution was as important as the scientific advances that led to the vaccine.
Not long after Sabin’s vaccine, another vaccine arrived to prevent another scourge of public health, measles. This vaccine led to the near eradication of measles within the US. Unfortunately, in recent years, social and political forces are on the verge of leading us back to situations like Kansas City but this time it is occurring in our schools. Part 5 in this series examines how the measles, mumps, and rubella vaccination rate is absurdly low in some US schools and the danger that this creates for all children. But this time the uneven distribution is brought about largely through vaccine exemptions.
Troy Tassier is a professor of economics at Fordham University and the author of The Rich Flee and the Poor Take the Bus: How Our Unequal Society Fails Us during Outbreaks.
Part 1: Asia: The Earliest Inoculations
Part 2: Inoculation in the North American colonies and Washington’s mandate
Part 3: A Safer Procedure and the Rise of New Vaccinations
Part 4: Vaccine Inequality and the Case of Polio
Part 5: Measles Vaccines and the Importance of School Mandates Today