3.7.3: Vaccines

In the first half of the 20th century, children were commonly stricken with poliomyelitis (commonly referred to as “polio”), a potentially deadly virus that could spread between people and was endemic - tending to break out each summer. Polio could cause paralysis of the limbs or even the diaphragm, leading to death or a lifelong sentence to an iron lung - a large iron chamber which causes air pressure changes, allowing those with a paralyzed diaphragm to breathe. Building on the work of Elise Ward, a zoologist who was able to grow the poliovirus in cell cultures, and Dr. Isabel Morgan, who successfully created the first killed-virus vaccine for polio (previous vaccines simply used a weakened version), Dr. Jonas Salk was able to create and test a vaccine which had 80-90% efficacy at preventing infection. Later, Dr. Albert Sabin created an oral version with attenuated (weakened) virus, which was even more effective and easier to administer. During the 1950s, these vaccines were widely circulated, such that 1979 saw the last case of polio in the U.S. However, the initial vaccine production had serious problems. Salk’s vaccines produced by a specific pharmaceutical company were found to have live virus in them instead of properly killed virus. A female virologist, Bernice Eddy, sounded the alarm but was ignored, and subsequently several hundred children were infected, paralyzed, or killed by the vaccine itself. This obviously produced distrust in the vaccine, which was supplanted by Sabin’s oral vaccine. Subsequently, infection with wild polio has been eradicated in all but a few countries where vaccine uptake has had challenges; largely due to misinformation regarding vaccines and resistance from the dominant political party (Martin, 2020, Contributors to Wikimedia projects, Polio vaccine, 2023f). See Figure \(\PageIndex{1}\) below. In very rare cases, Sabin’s vaccine also caused paralysis from the weakened virus itself reproducing in the intestines. The U.S. ceased its use in the year 2000, and have only used the inactivated version since. However, in some parts of the world the weakened vaccine is still used, and sometimes the vaccine-derived virus can be passed to unvaccinated people as well (Offit, 2023). Even with huge public health successes like the polio vaccines, caution and continued vigilance for viral mutation is warranted.

Figure \(\PageIndex{1}\): Polio Case and Death Rates in the U.S. 1900-2019. Data source: Our World In Data based on US Public Health Service; US Center for Disease Control; and WHO. (Copyright; CC-BY OurWorldInData.org/polio )

Many of our modern vaccines were first developed in the 1950s and 60s, and can be traced back to the researcher Dr. Maurice Hilleman. During his doctoral studies at the University of Chicago, he was the first to demonstrate that chlamydia was a bacterial and not viral infection (which meant it could be treated with antibiotics). Hilleman went on to develop vaccines for influenza, hepatitis b, pneumococcus, meningococcus, chicken pox, measles, mumps, and rubella, and also pioneered the combined measles, mumps, and rubella (MMR) vaccine. The mumps vaccine was actually developed from a strain of the mumps he gathered from his daughter, who at the time seemed to be coming down with the infection. This strain of the mumps is still used to create vaccines to this day. Although Dr. Hilleman was not one to revel in the spotlight, it is estimated that his work has prevented the deaths of more than 8 million people each year (The Children’s Hospital of Philadelphia, 2023).

Since the days of Jenner’s cowpox experiments, vaccine research has been one of the priorities of public health. This is because vaccines can often prevent severe diseases, infection, or even potentially eliminate a pathogen from circulating in humans. New technologies include using parts of a pathogen rather than the whole pathogen and/or using DNA or mRNA (messenger RNA) to elicit the immune system response, as was used in several of the COVID-19 vaccines (The College of Physicians of Philadelphia, 2023).