Cómo funciona la vacuna contra la COVID-19 de Pfizer-BioNTech
The German company BioNTech worked with Pfizer to develop and test a COVID-19 vaccine called BNT162b2with the generic name tozinameran or the brand Comirnaty. A clinical study showed that the vaccine had a 95 percent rate of effectiveness in preventing the disease.
A fragment of the coronavirus
The SARS-CoV-2 virus is filled with proteins that it uses to enter human cells. These proteins, called spikes, are tempting targets for potential vaccines and treatments.
Gene of
Protein from
the summit
Gene of
Protein from
the summit
Like Moderna's vaccine, Pfizer-BioNTech's vaccine relies on the virus' genetic instructions to assemble the spike protein.
MRNA in an oily envelope
The vaccine uses messenger RNA, the genetic material our cells read to make proteins. The molecule – abbreviated as mRNA – is fragile and our natural enzymes would tear it apart if injected directly into the body. To protect the vaccine, Pfizer and BioNTech wrap the mRNA in oily bubbles made of lipid nanoparticles.
Nanoparticles
of lipids
surround
mRNA
Nanoparticles
surrounded by lipids
mRNA
Due to their fragility, mRNA molecules are rapidly broken down at room temperature. Pfizer is building special containers with dry ice, heat sensors and GPS trackers to ensure vaccines can be transported at -70 degrees Celsius in order to remain viable.
Entry into a cell
After injection, the vaccine particles collide with the cells, fuse with them and release the mRNA. Cell molecules read their sequence and assemble spike proteins. In the end, the cell destroys the mRNA in the vaccine so that there are no more permanent traces.
Three proteins
Combine spike
Fragments
of spikes
and proteins
The gifts
Fragments
top
Three proteins
Combine spike
Fragments
of spikes
and proteins
The gifts
Fragments
top
Three proteins
Combine spike
Fragments
of spikes
and proteins
The gifts
Fragments
top
Three proteins
Combine spike
Fragments
of spikes
and proteins
The gifts
Fragments
top
Three proteins
Combine spike
Fragments
of spikes
and proteins
The gifts
Fragments
top
Three proteins
Combine spike
Fragments
of spikes
and proteins
The gifts
Fragments
top
Three proteins
Combine spike
Fragments
of spikes
and proteins
The gifts
Fragments
top
Some of the spike proteins form spikes that migrate to the surface of the cell and spread their tips. The vaccinated cells also separate into fragments some of the proteins that they present on their surface. The immune system can then recognize these protruding spikes and spike protein fragments.
Intruder detection
When a vaccinated cell dies, its remains contain many spike proteins and protein fragments, which can then take up a type of immune cell called an antigen-presenting cell.
Remains of a
dead cell
CELL
MODERATOR
OF ANTIGENS
Digestion of
Proteins
The gifts
a fragment of
Spike protein
Remains of a
dead cell
CELL
MODERATOR
OF ANTIGENS
Digestion of
Proteins
The gifts
a fragment of
Spike protein
Remains of a
dead cell
CELL
MODERATOR
OF ANTIGENS
Digestion of
Proteins
The gifts
a fragment of
Spike protein
The cell has fragments of the spike protein on its surface. When other cells called helper T lymphocytes recognize these fragments, the helper T lymphocytes can sound the alarm and prompt other immune cells to fight infection.
Formation of antibodies
Other immune cells called B lymphocytes could collide with coronavirus spikes on the surface of vaccinated cells or with fragments of floating spike proteins. Some B-lymphocytes may be able to attach to the spike proteins. Later, when helper T lymphocytes activate these B lymphocytes, they begin to multiply and secrete antibodies that attack the spike protein.
protein
associated
on the surface
Activation of
B lymphocytes
protein
associated
on the surface
Activation of
B lymphocytes
protein
associated
on the surface
Activation of
B lymphocytes
protein
associated
on the surface
Activation of
B lymphocytes
protein
associated
on the surface
Activation of
B lymphocytes
protein
associated
on the surface
Activation of
B lymphocytes
Activation of
B lymphocytes
protein
associated
on the surface
Activation of
B lymphocytes
protein
associated
on the surface
Activation of
B lymphocytes
protein
associated
on the surface
Activation of
B lymphocytes
Corresponding proteins
on the surface
Activation of
B lymphocytes
Corresponding proteins
on the surface
Activation of
B lymphocytes
Corresponding proteins
on the surface
Stop the virus
Antibodies can stick to the coronavirus spikes, marking the virus for destruction, and blocking the infection by preventing the spikes from attaching to other cells.
Suppression of infected cells
Antigen presenting cells can also activate another type of immune cell called a cytotoxic (or suppressive) T lymphocyte to search for and destroy coronavirus infected cells that have spike protein fragments on their surface.
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
CELL
MODERATOR
OF ANTIGENS
Presentation of
a fragment of
Spike protein
LYMPHOCYTE T.
ASSASSIN
ACTIVATED
Begins to suppress
to the infected cell
Memory of the virus
The Pfizer BioNTech vaccine requires two injections 21 days apart to keep the immune system as good as possible and fight the coronavirus. However, since the vaccine is new, researchers don't know how long its protection could last.
Second dose
21 days later
Second dose
21 days later
Second dose
21 days later
A preliminary study found that the vaccine offered strong protection around 10 days after the first dose compared to people who took a placebo:
Cumulative incidence of COVID-19
among the participants in the clinical study
People who took
a placebo
People who applied that
Pfizer BioNTech vaccine
Weeks after the first dose
Cumulative incidence of COVID-19
among the participants in the clinical study
People who took
a placebo
People who applied
the vaccine
Pfizer-BioNTech
Weeks after the first dose
The amount of antibodies and cytotoxic T lymphocytes may decrease in the months following inoculation. However, the immune system also contains special cells called memory B and T cells that can hold information about the coronavirus for years or even decades.
For more information on the vaccine, please visit: Pfizer's Covid Vaccine: 11 Things You Need To Know.
Preparation and injection
Each vial of the vaccine contains 5 doses of 0.3 milliliters. The vaccine must be thawed and diluted with saline before inoculation. The vial should be used within six hours of reconstitution.
A diluted vial of the vaccine in the Royal Free Hospital, LondonJack Hill / Agence France-Presse
Sources: National Center for Information on Biotechnology; Nature; Florian Krammer, Icahn School of Medicine on Mount Sinai.
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