This post is a part of a series on COVID-19 and the Coronavirus Pandemic
Science deserves all credit for the development of vaccines that will slow the spread of the novel coronavirus. While acknowledgement should certainly be given to those who have provided resources for the research, ultimately these individuals or organizations could not develop a vaccine without science. And those that have decided to selectively embrace science behind the development of a vaccine, while sidelining the science on nearly all other issues for political reasons, certainly do not deserve credit.
Science has always been behind the development of vaccines throughout history. As someone who has a bachelors, masters, and Ph.D. in biology – my training in cellular biology, including understanding the human immune response, has reinforced to me just how far science has come on vaccine development through many years of research. Here is a look at the history behind the science of vaccine development and our basic and current understanding of how and why vaccines work.
The first vaccine
We understand so much more regarding the science underlying vaccinations than we did hundreds of years ago when the first vaccination was developed for smallpox, which has been present in human society since at least the 3rd century BCE. During the 18th century it is estimated that half a million Europeans died of smallpox every year! And during the 20th century, smallpox still killed between 300-500 million people.
But not everyone who contracted smallpox died from the disease; some individuals became immune. By the Middle Ages, a Buddhist nun had developed a process to develop immunity in the population. The process involved taking scabs from individuals infected with smallpox, allowing the scabs to dry, grinding up the dried scab tissue, and then placing the tissue in cotton. The concoction was then blown into the noses of uninfected individuals using a pipe. The process was called “insufflation” and although it was not the most effective process, it is the first documented case of humans deliberately infecting each other to develop immunity.
This process was eventually introduced to Europe in the early 18th century. The process was modified with the choice of implementation tool becoming a needle and syringe; the process also became known as “variolation.”
A physician, Dr. Edward Jenner, became interested in milk maids who sometimes contracted a similar but much milder version of smallpox from cattle known as “cowpox.” Dr. Jenner created a cowpox concoction that he administered to a young boy who developed immunity to smallpox. Dr. Jenner developed a scientific name for cowpox calling it Variola vaccinia, based off the Latin word for cow, “vacca,” and the procedure he used that he called, “vaccination.” He then sent the vaccination to multiple medical acquaintances who vaccinated individuals around Europe.
People continued vaccinating against smallpox in the ensuing decades, and following a major international public health campaign in 1980 the World Health Organization declared the disease eradicated.
But why did this vaccination process work?
Early scientists and physicians knew vaccines were helping protect people from deadly diseases but did not fully understand why vaccinating people worked. To fully understand how vaccines work, scientists needed to understand how our bodies respond and protect us from infectious diseases.
What scientists have now discovered is that our immune system cannot be pinned to a single organ, cell, or type of tissue – it involves multiple cellular structures (e.g., white blood cells, bone marrow, lymphocytes, skin). We now also understand from science that the immune system can be broken up into two different types of systems: the innate system and the adaptive system.
The innate system is made up of what you have been born with that attempts to fight off any and all pathogens. The innate system includes your skin, mucous membranes, or non-specific cells that can trap microbes – for example cells called macrophages that can eat pathogens and destroy them (see this video for a demonstration). However, the innate system can encounter pathogens that overpower their defenses, which is when the adaptive system plays a key role in our immune response.
Understanding how our adaptive system works is the key to understanding how to develop vaccines that ward off strong and potentially lethal pathogens. Scientists have discovered that our adaptive system is complicated, but for the sake of simplicity the adaptive system involves two major types of cells in your body called B cells that produce antibodies to identify a pathogen and T cells that destroy cells that have become infected.
The adaptive system is risky because it takes time for your body to learn how to build up defenses to defeat a novel pathogen. During this time, the pathogen may do lots of harm to the body, especially if a person is very young or old and has a weakened immune system or is immunocompromised in some other way. Even individuals who are otherwise healthy may have tissue or organ damage from a pathogen that our body does not know how to immediately fight off.
The long time it can take our immune response to kick in to protect us from a novel pathogen is one reason that a vaccine is so important. And scientists have used their understanding of how our adaptive system works to develop vaccines so we are protected from a novel pathogen before it can even find its way inside our cells.
What is a vaccine exactly then?
A vaccine is essentially a weakened, dead, or piece of a pathogen that is injected into your body so that your adaptive immune system kicks into high gear to identify it, destroy it, and remember it – all while not making you incredibly sick since the pathogen is already dead or weakened. Each vaccine created is unique to the specific pathogen it is attempting to destroy, and they can be developed through different processes.
There are many different classes of vaccines that can be developed that elicit different types of immune responses and have pros and cons. Scientists can create vaccines using weakened pathogens that are still living when they are injected into your body – these are called “live attenuated vaccines.” While these types of vaccines often can instill long-term immunity, they can be quite complicated to make and because they are made-up of the living pathogen, people with weaker immune systems cannot receive them. Scientists can also develop vaccines with dead pathogens that are safer to give to those who are immunocompromised, but these often do not create long-lasting immunity. Another type of vaccine, called a subunit vaccine, uses an isolated antigen from a pathogen (the ingredient that triggers the immune response). Scientists can break these antigens down further to isolate proteins that elicit a specific immune response.
Scientists are now developing a whole new swath of vaccines that rely on the use of RNA or DNA. These vaccines isolate specific genes that once inserted into the body instruct cells to make a specific antigen that triggers the adaptive immune response. These vaccines not only confer immunity, they can also be safely given to those immunocompromised since they do not have any parts of the pathogen that could turn into a disease and harm the patient, and they can be mass produced quite easily. However, these types of vaccines are relatively new and their development process is still evolving.
Vaccine science is still evolving
Our scientific understanding of the human immune system and how we can strengthen it through vaccines has come a long way since the first smallpox vaccine, but there is still much to learn! One thing is clear – science is why we understand what we do about the way our immune system works and how to develop vaccines.
There have certainly been folks that have funded this kind of work along the way and politicians that have worked hard to free up resources for vaccine research. But at the end of the day, they do not do the science, and have played no role throughout history in making scientific discoveries. When we do end up with a vaccine that is effective and safe against the novel coronavirus, trust me that there is a rich history of scientific research that shows the development will be because of science – not because of some politician who’d like to take credit.
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