Immunity and vaccines go together like Corona and lime, (sorry, too soon?). Anyway, my point is that vaccines function to boost and support your natural immune system so that it can cope with new challenges and well known, terrible diseases. People have been looking at these techniques since the 15th century, and we sure have come a long way since then!
First, let’s get familiar with our immune systems. The immune system is separated into two main subsystems, namely the innate (or general) and the adaptive system. The names pretty much sum up the difference between the two. The innate system has broad-spectrum protection which includes the first line of defense mechanisms like skin, mucous membranes, body temperature, fever and stomach acid. It also consists of some nifty little ninjas that circulate through the blood and that fight off foreign or sketchy invaders. Therefore, your innate immune system can sometimes handle the threat without needing back up from the adaptive system.
The adaptive system is a really cool organization of specialized cells and responses that learn from previous infections and remember how to fight it off. It responds to an infection with specialized attack plans that means it can react faster when it encounters the same invader more than once. There are some key players in the innate immune response: T-cells and B-cells/antibodies. We have all heard of antibodies, but an especially important antibody is immunoglobulin G (IgG), which is the most common antibody in our blood and is vital in vaccination and immunization processes.
There are different types of immunization, both active and passive, as well as natural and artificial. Natural refers to exposure to the environment and other people and animals, whereas artificial refers to medical interventions. These medical interventions include vaccination. Vaccines are designed to, ideally, trigger the innate and adaptive immune system. However, this may not always be possible, and some vaccines may need to focus on one of the systems.
There are different types of vaccines, and I will quickly go through some now. There are live attenuated vaccines where the pathogen is weakened therefore your body can make the correct antibodies without getting sick, an example would be measles. Then there are inactive vaccines where the pathogen has been killed through chemical, heat, or radiation damage (eg, influenza). Subunit vaccines (eg, hepatitis B) where part of the antibody recognition signal is included to trigger a response. Toxoid vaccines (eg, tetanus) are made by inactivating the bacterial toxins, and so the immune system responds against the toxins. Conjugate vaccines (eg, Haemophilus influenzae type B) are a specialized version of subunit vaccines. Naked DNA vaccines are pretty new but are promising and use specific DNA to stimulate immunity (this technique is being used to try to develop vaccines for influenza and herpes). Recombinant vector vaccines are still being tested with either attenuated viruses or bacteria to introduce pathogen DNA into cells. They would mimic a natural infection, thereby triggering an immune response.
With all of these exciting vaccine techniques being used to provide immunity, we can be hopeful that perhaps we have a vaccine against Covid-19. But we need to remember that it takes months to test the vaccine to ensure that they are safe to use!
PS. Vaccines DO NOT cause autism.
Clem, A., 2011 Fundamentals of vaccine immunology. J Global Infect Dis. 3: 1.
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