Back in 2020, we wrote about Herd Immunity and the key role vaccines would play in getting us out of the Covid-19 Pandemic. Fast forward to 2021, and the rapid development of vaccines has landed us on the cusp of making this a reality. Yet, with pitfalls in the roll-out of the Oxford-AstraZeneca vaccine and unprecedented levels of misinformation and public distrust of governments, scientists and traditional media, vaccine skepticism is growing. In the USA, 25% of adults polled said they would not get the vaccine. Closer to home, the available data to date in several Caribbean countries puts vaccine hesitancy in the range of 32-62% of adults polled. Here, we unpack vaccines in two parts. This week we're going back to basics on the history and science behind vaccines: how vaccines were first developed, they they work and what's actually in them.
First, some historical context. Let’s travel back in time, to the 18th century, and to the peak of the smallpox pandemic:
The perils of the pre-vaccine era and the birth of vaccines
The story of the development of vaccines can’t be told without the story of smallpox. Smallpox had been with us for millennia, with the earliest known evidence coming from the tomb of the Egyptian pharaoh, Ramses V, and remained endemic in every continent until its successful eradication by the WHO in 1980. The disease, caused by two variants of the variola virus, manifested in the form of painful pustules all over the body. Victims of the more severe form of the virus, variola major, suffered around a 30% mortality rate, with infant mortality rate rising as high as 80-98% in some places, while survivors of the disease would be marked for life with scars in the places the pustules had formed. In the 17th and 18th centuries, increased population sizes in urban centers, along with increasing global movement and colonization, led to explosions in the numbers of smallpox cases. Experts estimate that an unfathomable half a billion people died of smallpox in the last hundred years before its eradication, corresponding to 5 million deaths annually for that century. {See here for lots of stats from the history of smallpox.}
The untold suffering caused by the disease drove people to extreme measures to protect themselves. A practice called variolation, a crude and risky form of inoculation, was developed in several continents. Here, individuals who had never been infected by the smallpox virus exposed themselves to minute amounts of infected material from the pustules of diseased individuals, by inhaling or scratching it into their skin. This usually resulted in the symptoms of smallpox, but fewer deaths - around 1-2% compared to the 30% morality in naturally infected smallpox cases.
The key breakthrough in the development of the vaccine came in 1796, when English doctor Edward Jenner discovered that individuals who had contracted cowpox, a much milder disease, were somehow naturally immune to smallpox - the details of this are beyond the scope of this article, but click here or here for the whole, fascinating story. After his discovery, Jenner embarked on a campaign to inoculate the public with cowpox, paving the way for the invention of the modern vaccine, a term which Jenner himself coined, naming it after the Latin term for “cowpox”- vaccinia.
Modern Vaccines 101
How do they work?
Today, we have a much better understanding of how vaccines interact with our immune systems to prevent disease. This is essentially how it works. In order for our bodies to fight off a viral or bacterial infection, our immune system must first be able to detect the pathogenic cells lurking in our bodies. Luckily, all viruses and bacteria have unique molecules on the surface of their cells, called antigens, that our immune systems can use to identify them and mark them for destruction. To do this, we produce antibodies, which are tiny proteins that stick to these unique surface molecules on the virus, which then signal to other cells to attack. However, the production of antibodies takes valuable time, as our immune system must first detect the novel virus and then manufacture the specific antibody required to fight the infection. By the time antibodies are produced in great enough quantities to fight the virus, the virus may have replicated so much that the infection becomes difficult to contain and the body becomes overwhelmed. However, if we survive the infection, a small number of these unique antibodies stay in our system, just to keep on the lookout for any future attacks by this virus. When our bodies are re-infected, our antibodies detect the virus right away, ramp up production of more antibodies and the virus is quickly vanquished before the infection takes hold. {Learn more here} This is the basic principle that we use in all vaccines. In the case of Edward Jenner’s smallpox vaccine, the antigens on the cowpox virus were similar enough to those on the smallpox virus, such that patients inoculated with cowpox already had special antibodies in their systems that could fight off a smallpox infection later on.
What’s in them?
Luckily for us, modern vaccines are no longer made with live and active pathogens like Jenner’s smallpox vaccine. Today, the exact material used varies between pathogens, but will contain one of the following:
Antigens- those surface molecules from the pathogen that the body can recognise, or a toxin produced by the pathogen. These are purified and killed with chemicals to render them inert. | Used in the Hepatitis B Vaccine
A “dead” form of the pathogen- the pathogen is treated with chemicals so its genetic blueprint is destroyed and is no longer able to replicate, but the body is still able to recognize it from its antigens. | Used in the Polio Vaccine
A weakened form of the pathogen- the pathogen is treated so it can only replicate very slowly in specific laboratory conditions, but is unable to replicate in the body, but again, is recognized from its antigens | Used in the MMR Vaccine
What else is in them?
Along with the key pathogen compounds, vaccines contain other ingredients which help those active compounds do their job. See here for a comprehensive list of vaccine additives from the Centers for Disease Control and Prevention. What’s useful about this list, is it outlines the role these compounds play in making vaccines effective, as well as where in our normal everyday lives we come into contact with these compounds (spoiler: they’re in our food, water, cosmetics, the environment, and naturally occur in our bodies).
Why do I sometimes feel sick after a vaccine?
Sometimes a vaccine will cause soreness at the site of the injection, a fever, or flu-like symptoms. This is usually because of the immune system going to work on the pathogen-derived compounds in the vaccine. From your body’s point of view, the vaccine looks like an actual attack from the pathogen, so it triggers an immune response and starts pumping out antibodies just as it’s supposed to.
Who shouldn’t take vaccines?
For patients whose immune systems are not functioning properly - due to a disease or immuno-suppressant drugs - certain vaccines are not recommended. Patients will be informed of this in their consultations with doctors before getting any vaccines. {Learn more here.}
This story goes much deeper than this...
Why are we still having a conversation about the safety and efficacy of vaccines, over two hundred years after their invention? Ever since the advent of vaccines, public skepticism has existed about their safety and effectiveness. In recent years, this skepticism has gained new life through the anti-vax movement, resulting in upticks in the levels of diseases such as measles and mumps, once thought to be things of the past. With the current pandemic, and the roll out for new vaccines for Covid-19, these fears have been amplified. Check back next week to read part two of this topic, on vaccine skepticism through the ages, and what you need to know about the Oxford-Astrazeneca Covid vaccine controversy.