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The first administrations of the Pfizer-BioNTech coronavirus vaccine in Italy, and in much of the rest of the European Union, began on December 27. The number of available doses is still limited, but it will increase significantly in the first weeks of January, with the possibility of vaccinating health and social-health personnel first and the guests of various types of rest and nursing homes. The vaccine took less than a year to develop and, along with the next one in the authorization phase or in the final stages of testing, could go a long way toward keeping the pandemic under control.
Less than a year
In January, the German biotechnology company BioNTech analyzed the first information about the newly discovered coronavirus (SARS-CoV-2) in China, concluding that it had a high probability of spreading to the rest of the world and causing a pandemic. He then set about developing a next-generation vaccine based on messenger RNA (mRNA), the molecule that encodes and carries the instructions contained in DNA to make proteins.
BioNTech is a relatively small company, so in the first months of this year it began to look for a company with which to collaborate in the project, finding the interest of the American pharmaceutical multinational Pfizer. In May, the two companies launched the first clinical trials of two versions of the vaccine, noting that the so-called BNT162b2 resulted in fewer adverse reactions, making it the candidate vaccine.
As governments began formulating the first billion dollar contract reserves, Pfizer and BioNTech began clinical trials of step 3, the most important for detecting the effectiveness of the vaccine, involved 30,000 volunteers, and then increased the number of participants in the fall to 40,000. In addition to being safe, the vaccine has been shown to be 95 percent effective when given two doses three weeks apart. The Pfizer-BioNTech vaccine was licensed in the United Kingdom on December 2, in the United States on December 11, and in the European Union on December 21.
The development of the vaccine was financed by Pfizer and with public investments, including 375 million euros from the German government and 100 million euros from the European Union.
Name
The Pfizer-BioNTech vaccine is indicated by the code BNT162b2, has the non-commercial name Tozinameran, linked to its active ingredient, and the commercial name Comirnaty.
SARS-CoV-2
To evade the defenses of the cells of our body, the SARS-CoV-2 coronavirus uses some proteins present in the peaks found in its outer layer. These bind to the cell membrane and are able to overcome its defenses, allowing the virus to inject its own genetic material (RNA) and then induce the cell to produce new copies of the coronavirus, which in turn can bind to others. virus-carrying cells. ‘infection.
Stylized version of the coronavirus, on its surface there are peaks that contain the proteins that are capable of joining the cells of our body; the black line shows the genetic material (RNA) that the coronavirus then injects into the cell to replicate (Wikimedia)
MRNA
The vaccine uses a synthetic form of mRNA, then made in the laboratory, with instructions that our cells can read to make particular proteins. The mRNA is very easily damaged and would be rapidly destroyed by the body’s defenses shortly after injection. For this reason, researchers have found a way to protect the molecule by inserting it into tiny oily bubbles (made up of lipid nanoparticles), which complicate the life of enzymes that are activated to destroy foreign substances.
Cold
However, mRNA molecules are very fragile even outside of our body. For this reason, the Pfizer-BioNTech vaccine should be stored at -70 ° C and used within a few hours after thawing. Pfizer has developed several solutions to maintain such low temperatures while transporting doses, while clinics and hospitals are preparing to have freezers powerful enough to keep vaccine doses stable.
Entry
After receiving a dose, the vaccine particles come into contact with the cells and release the mRNA. Inside are instructions for building the proteins found at the tips of the coronavirus, without making the other more dangerous parts of the virus. The cells follow the instructions and build these proteins, at the end of the process the mRNA is destroyed without leaving traces.
Some of the new proteins produced reach the outer part of the cell membrane forming peaks similar to those of the coronavirus, while other of its fragments are exposed by the cells of its membrane.
(BioNTech)
Alarm
At the end of its life cycle, the cell dies and its fragments remain, which are eliminated by other specialized cleaning cells. During this process, coronavirus proteins can come into contact with an antigen-presenting cell (APC), a type of immune system cell capable of displaying particular antigens (foreign bodies) on its surface to enhance their presence.
Among the first to notice are T helper lymphocytes, cells that act as lookouts and when they notice something strange they alert other cells of the immune system to intervene.
Antibodies
Meanwhile, other immune cells, the B lymphocytes, which are circulating in the body, can accidentally end up in contact with cells that have received the mRNA and that following their instructions have produced the coronavirus protein, exposing it to their cell membrane. . The B lymphocytes bind to these new proteins, but they don’t really know what to do. Things change when they encounter a helper T lymphocyte in their path, which sounds the alarm and then activates them, prompting them to multiply and produce antibodies to counter the protein.
The consequence is the production of a huge amount of antibodies that remain in circulation in our body. In the event that one comes into contact with the actual coronavirus, the immune system has the tools to recognize the protein at its dangerous tips. Antibodies bind to these to prevent them from coming into contact with cell membranes, evading their defenses.
(Siemens Healthineers)
Extermination
Helper T lymphocytes also sound the alarm for another type of immune system cell, cytotoxic T lymphocytes, activating them to kill any cells displaying the coronavirus protein on their surface, indicating that they have been infected.
Immune system
The combination of helper T lymphocytes, B lymphocytes, cytotoxic T lymphocytes, and other defense mechanisms can only work if the immune system has learned to recognize the coronavirus protein. The mRNA vaccine does just that: educate our immune systems, without having to learn these things in the most difficult and dangerous way with the real coronavirus.
Memory
To date, we do not know how long the immune system stores in memory what it learns through this system, simply because the vaccine has been used for such a short time. However, it was found that a first dose already confers strong protection, which is significantly strengthened after the second three weeks later.
It will be several months before you know how long your vaccine coverage lasts. The number of antibodies and lymphocytes that have specialized is likely to decrease over time. However, the immune system is very complex and has a wide variety of cells that help us defend ourselves, so the information to counteract the coronavirus could remain in your memory in another place and for a long time.
Administration
The Pfizer-BioNTech vaccine is given by injection in the arm, just below the shoulder. Each vial allows 5 vaccines, with a single dose of 0.3 milliliters, which is diluted with saline before injecting. With precision syringes, you can reduce waste and get 6-7 vaccines from a single vial.
Before use, the vaccine should be allowed to thaw from -70 ° C to a temperature of a few degrees, comparable to that of a refrigerator. After thawing, the contents of the vial should be used within 6 hours.
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