Macrocosm: Everything You Should Know About Vaccines

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On May 14, 1796, Edward Jenner made a controversial decision that would change the course of history and prevent countless future deaths. At the time, smallpox ravaged the world, killing 400,000 people annually in Europe alone. Working as a doctor on the English countryside, Jenner observed that milkmaids who contracted cowpox, a mild disease, were protected against smallpox. To test this theory, Jenner inoculated 8-year-old James Phipps with pus from a blister on the hand of Sarah Nelmes, a milkmaid who had caught cowpox. Weeks later, Jenner deliberately exposed Phipps to a real case of smallpox and discovered that the boy had developed immunity against the disease. Almost two centuries later, in 1980, the World Health Organization would declare smallpox officially eradicated after a mass vaccination campaign.

Since that fateful day, vaccination has been hailed as the greatest medical advancement of all time. Yet, in recent years, it has become a source of great contention across the globe. Diseases thought to be eradicated thanks to vaccination are reemerging. The recent COVID-19 pandemic has shifted the conversation in an unexpected direction. This historical moment has been marked by quarantines, social distancing, and feelings of isolation. From the very beginning we’ve been promised a return to normalcy once a vaccine is devolved and experts are hopeful one will be ready by early 2021. As we eagerly await, many are left scratching their heads and asking questions. 

What is a Vaccine?

Vaccination is not a medical treatment; it is strictly a preventive measure meant to provide protection before infection. Vaccines are used to elicit a natural immune response without causing an actual disease. They vary in protection so some are given only once, whilst others may require a booster shot every so often. Vaccines are typically made against viruses, not bacteria. Although some bacterial vaccines exist, bacterial infections can easily be treated with antibiotics, something that does not work on viruses. Each vaccine falls under one of the 3 major categories: live-attenuated, killed, and subunit.

Live-attenuated vaccines are made from an intentionally weakened form of the natural virus. The resulting pathogen is still replication competent. Once in the body, it is able to travel to the same location the virus would normally go. There its replicates, triggers an immune response, and helps to boost immunity at the natural site of reproduction. The immune response this type of vaccine elicits is powerful, inducing antibodies and leaving behind memory immune cells to fight future infections. The one down side to using a live-attenuated vaccine is that it is more likely to cause disease, especially in immunocompromised individuals.

A killed vaccine contains a pathogen that has been inactivated in some way. In doing this, the virus can no longer replicate. Killed vaccines are generally considered safer than live-attenuated vaccines because their modification makes it impossible for them to mutate so they are less likely to cause disease. The disadvantage of killed vaccines is that they tend to be less effective, thus multiple doses are usually given. Inactivation can destroy the immune protection of some proteins so these vaccines don’t elicit a great immune response.

Subunit vaccines only use a portion of the virus, not the whole virus. For example, the HPV vaccine is made of only the viral capsid, the outer ‘shell’ of the virus, and does not contain any of the genetic material that should be inside of it. With this type of vaccine, there is a reduced risk of adverse effects. The virus cannot replicate or mutate so it has no chance of infection because it isn’t fully functional. This could be the simplest type of vaccine to produce, but the specific viral component that is protective must be known. A requirement that isn’t always simple or easy to fulfill.

How do Vaccines Interact with the Immune System?

Your immune system is one of the most fascinating and essential characters in the story of your body. It is a coordinated network of proteins, cells, tissues, and organs working together to defend you against foreign invaders. The immune system is most comparable to a military defense strategy with its many moving parts and multiple layers of defense. The very first is barriers: anatomic (skin, stomach acid, saliva, tears, etc.), physiologic (body temperature and pH), chemical, microflora, and inflammation. The second consists of specialized cells specifically designed to slow and reduce infection. The first and second lines of defense are commonly referred to as the innate immune response. 

When innate immunity fails to control an infection, it calls on adaptive immunity for back-up. The adaptive immune response consists of the most recognizable components of the immune system: T cells and B cells. These immune cells destroy invading pathogens and the toxic molecules they produce. They are highly specific and able to provide lifelong protection.

Each T cell is unique and specific to a single antigen. So yes, we have billions of T cells, one for every antigen in existence. T cells spend most of our lifetime in a naïve state and are activated when receptors on the T cell’s surface recognize their corresponding antigen. Once activated, the T cell quickly multiplies and begins to fight off the infection. When the infection is cleared, many of the T cell clones die by apoptosis, a form of cell suicide, and only the best T cells remain: the memory T cells. Memory T cells have become "experienced" by having encountered an antigen during a prior infection. At a second encounter with the invader, these cells can quickly reproduce to mount a stronger immune response. 

Like T cells, B cells are highly specific, have a receptor that will recognize a single antigen, and will proliferate when activated. In a sticking difference, B cells need a confirmation from a subset of T cells known as helper T cells before that can happen. The T cell cannot perform this function unless it too has been activated. This is the immune systems version of checks and balances. The main function of B cells is to pump out antibodies, proteins that specialize in antigen removal. Antibodies are also specific to a single antigen but there are multiple classes, or types, of antibodies. B cells are unique in that they can switch between releasing different classes of antibodies without compromising specificity. Once the threat has been defeated, memory B cells will also remain circulating throughout the body.

Vaccines introduce antigens into our systems in order to stimulate the body’s immune system. These nonpathogenic organisms are recognized as a threat, destroyed, and a record is kept of them. When the individual is actually infected with a pathogen, the body mounts a very quick and effective response. The ultimate goal of vaccination is to provide memory cells that last the entire lifetime of an individual.

Are Vaccines Safe?

Since their very conception back in 1796, the safety of vaccines has been a concern to the general public. In the past few decades, misinformation has spread like wildfire leading to the reemergence of doubt surrounding vaccine safety. In 1998, Andrew Wakefield and colleagues published a report in The Lancet medical journal linking the MMR vaccine to autism. The study was found to have misrepresented data, was deemed fraudulent, and was retracted in 2010. The UK General Medical Council found Wakefield guilty of serious professional misconduct and revoked his medical license. These actions unfortunately came too late as a seed of doubt had already been planted deeply into the minds of many.

Not ones to give up, Anti-vaxxers have used the simultaneous increase in the number of children diagnosed with autism and mercury content found in vaccines to justify their beliefs. Correlation doesn’t always equal causation. Yes, since the 1990s autism cases and infant exposure to mercury in vaccines have increased at a similar rate. But so has the divorce rate in Maine and the per capita consumption of margarine in the United States.

Top Credit: https://doi.org/10.1016/S0749-3797(03)00113-2

Bottom Credit: US Census & USDA

Obviously, two unrelated phenomena can be manipulated to appear connected even when they have absolutely nothing to do with one another. Information found on the internet should always be taken with a grain of salt unless it comes from a verified and legitimate source. Until now, there is no scientific evidence linking vaccines to autism.

Any medical procedure, has its risks. Vaccines are no different. As stated earlier, some vaccines can cause disease in immunocompromised patients. The most common side effects of vaccination are mild in nature and more serious side effects are extremely rare. For every 1 million vaccinations, only 1 to 2 may result in a severe allergic reaction. Vaccines are strictly regulated by FDA and must be tested rigorously before they are recommended for use by the CDC. This makes vaccines infinitely safer than the disease they prevent.

Why Should I Care?

Vaccines exploit systems already in place to help us fight off serious illnesses effectively for our entire lifetimes. A feat that is insanely impressive when you think about it. Rampant spread of misinformation has caused their safety to unjustly come under question. This made sense in Jenner’s time when vaccination was new and scientists still believed in “special creation”. For centuries, they have proven themselves time and time again leading to the end, or near end, of smallpox, polio, and malaria. Right now, in this moment in time, we need them more than ever. As COVID-19 ravishes the globe, a vaccine may be our only hope for a return to normal life.