Ever since the pandemic began, there has been a global race to prepare a vaccine to combat the SARS-CoV-2. Multiple countries working around the clock to protect their citizens from the virus and trying their best to make a vaccine. One such vaccine was made possible through a partnership between the German company BioNTech and Pfizer. They developed and tested a vaccine with a 95% efficacy rate known as BNT162b2. If that’s too much of a tongue twister then may I suggest its generic name Tozinameran, or perhaps the brand name: Comirnaty. Yeah... let’s just stick with “Pfizer-BioNTech Vaccine” for now.
How it all started
In the January of 2020, Dr. Ugur Sahin – one of BioNTech’s founders – was convinced that the COVID-19 disease in China would become a pandemic and the company began work on a vaccine; two months before the collaboration with Pfizer. In May, trials began on two versions of the vaccine and BNT162b2 had little to no side effects. The following months saw the Pfizer-BioNTech Vaccine’s successful trials and governments around the world voiced their approval for it, including the United States of America, United Kingdom, Argentina, Brazil, Germany and many others. Now, Pfizer expects to produce up to 1.3 billion doses in 2021 with each vaccinated person requiring two doses.
How is it different and how does it work?
Traditional vaccines for any disease involves injecting dead or weakened pathogens - of the disease for which the vaccine is intended – into the body. The person’s immune system easily wipes them out and produces antibodies which help the body remember how to fight off the pathogen if it were to ever enter the body again, hence, creating immunity to the disease. The COVID-19 vaccine made by Sinopharm works this way. The Pfizer-BioNTech Vaccine however, is much more complex. The virus’ fragile messenger RNA (or mRNA for short) is protected in an oily lipid (fat) nanoparticle and injected into the body. The vaccine is stored and transported at -70 degrees Celsius (-94 degrees Fahrenheit) to remain viable.
When the vaccine particles enter the body, they fuse into our cells mRNA’s genetic sequence is read by our cell molecules to create spike proteins similar to the ones present on the surface of the SARS-CoV-2, after which it is destroyed, leaving no trace. Some of the manufactured spike proteins travel to our cell surfaces and stick out. When the cell dies, the spike proteins exist alongside the debris. Antigen-Presenting cells of our immune system may come across these spike proteins (either as debris or existing on the surface of a vaccinated cell) and will take them up and then present fragments of the spikes on its surface which are then detected by Helper T Cells and an alarm is raised. The B Cells are then marshalled who attach onto the spike proteins and pour out antibodies against them after being activated by Helper T Cells. When the virus enters the body for real, the already-created-antibodies latch onto their spikes (which are the same as the spike proteins created by the vaccine)and prevent them from attacking our cells, and the virus dies out after being unable to find a host.
Now what about side effects caused by the vaccine? The Antigen-Presenting cells activate Killer T Cells that are programmed to kill cells that display the virus spike proteins on their surface. This leads to symptoms such as headaches, fever, chills, muscle pains, nausea, etc. However, the symptoms differ from person to person and sometimes there may be no symptoms at all! Being asymptomatic doesn’t mean that the vaccine is ineffective, it just means that you are responding differently to it.
Why two doses?
Early studies showed that a single dose of the Pfizer-BioNTech vaccine provoked a relatively weak immune response as compared to two doses. This also goes for the vaccine made by Moderna and it too works using the aforementioned mRNA method. In simple terms: the first dose of the vaccine builds up immunity and the second greatly reinforces it. An analogy would be: you are trying to move a heavy table across the room and only make it to the middle before another person joins you and you’re able to easily move it the rest of the way. There are many other vaccines that require two doses such as the Measles-Mumps-Rubella vaccine, vaccines against Hepatitis A and Hepatitis B, and the Shingles vaccine.
Immunity achieved?
The Pfizer-BioNTech vaccine requires a 21 day gap in between the first and second dose. The immunity process takes a fortnight after the second dose so you may fall ill if exposed to the virus shortly after your vaccination. The time between doses is needed to allow the first dose to develop the spike proteins and generate a bit of immunity. It is currently unknown whether delaying the second dose for a long period of time has an effect on immunity. Clinical trials showed that vaccine efficiency between the two doses is 52% but is 89%-91% effective fifteen days after the second dose. Calm down there, I did not lie to you; vaccine efficacy was observed to have reached 95% a week after the second dose. Even though the overall antibody count slowly decreased with time, they still remained high enough to be very effective. The bottom line: Yes, the Pfizer-BioNTech vaccine is safe and very effective in providing immunity to COVID-19.
Sources:
https://www.nytimes.com/interactive/2020/health/pfizer-biontech-covid-19-vaccine.html
https://www.healthline.com/health/why-two-doses-of-covid-vaccine#why-a-second-dose
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