Nobody likes to go into battle cold. The military trains -constantly running scenarios based on experiences and intelligence; Professional fighters use sparring partners that almost caricaturize their opponent’s style; all college students like to have study guides before taking an exam. Vaccines are all basically really good study guides/ sparing partners for your immune system; they introduce your immune system to harmless versions of a known enemy to give it some practice before the big day, if that day ever comes. If it does, your immune system will have studied the threat and more effectively kick some a** by mounting a faster response.
Our working definition for a vaccine will be a harmless version of a known threat that is meant to be introduced into the body in order to help the immune system recognize the real threat, and mount a more effective response.
Today there are two main approaches to introducing your body’s immune system to a harmless version of a know threat. The classic method has been to inject your body with the threat after it has been killed by heat or inactivated by other means. This method has been around for a while. The first Polio vaccine (~1950) and the new Sinovac COVID vaccine (CoronaVac) work like this, but we’ll get to that. On the other hand, mRNA vaccines like Pfizer’s and Moderna’s do not introduce the virus itself. Instead, they introduce a piece of mRNA that indirectly introduces a very important fragment of the virus. This simple but elegant application of the guiding principle of molecular biology (“central dogma” for short), is the cutting edge.
The take home is that there are two main types of vaccine:
Injection of real, but inactivated viruses (Sinovac)
Injection of mRNA that produces a fragment of the virus (Pfizer & Moderna)
Viral offense and Vaccine-enhanced immune system defense: Sinovac vs Moderna/Pfizer
In a nutshell, a successful infection is the result of the corona virus entering your body, and infecting individual cells. Once the cell has been hijacked, the virus injects a blueprint for how to manufacture copies of itself (RNA). The virus then uses your cells manufacturing machinery to read the RNA blueprint and manufacture millions of copies of itself. The viral copies then burst out of the cell to continue the rounds of infection, guile and destruction.
Anatomy of coronavirus
The corona virus is a sphere packed with a large RNA genome, and contains spiked keys on it’s surface that it uses to enter your body’s cells. In order for your body to block the virus from infecting cells, it must quickly identify the virus as a threat and understand how the virus is gaining entry to cells -the spikes in the case of coronavirus. Some people’s adaptive immune system does this better than others, and this is why it’s important to ‘boost’ your immune system through the various ways. A vaccine is one of those ways.
Sinovac works by basically inactivating the virus’ genes so that it cannot make more copies of itself (like removing the teeth and claws from the lion), and injecting it into your body. The virus, once injected, then uses it’s spikes to infect your cells where it is then studied by the key players of your immune system. A good illustrated overview about this particular vaccine and its efficacy has been published by NY times HERE.
Moderna & Pfizer work by injecting your body with the blueprint for how to manufacture the spike, not the whole virus, in the form of mRNA. Once the spike is manufactured inside of your body, your immune system studies the it. Having been trained on this particular feature, your immune system will recognize it quickly when it’s worn by the enemy, and mount a fast response. A good overview of these vaccines have been published by NY times HERE.
The response of your immune system to the real coronavirus in both vaccine scenarios (Sinovac and Moderna/Pfizer) is theoretically much faster and thereby effective than if it went into the fight cold, without practice. However, differences in effectiveness have been demonstrated.
As always…
References
Coronavirus: https://pubmed.ncbi.nlm.nih.gov/25720466/
Different types of vaccines: https://www.historyofvaccines.org/index.php/content/articles/different-types-vaccines
Nytimes Moderna: https://www.nytimes.com/interactive/2020/health/moderna-covid-19-vaccine.html
Nytimes Sinovac: https://www.nytimes.com/interactive/2020/health/sinovac-covid-19-vaccine.html