How Pfizer’s Vaccine Works – The New York Times
The German company BioNTech has worked with Pfizer to develop and test a coronavirus vaccine called BNT162b2. A clinical study showed that the vaccine had a 95 percent effectiveness rate in preventing Covid-19.
A piece of the coronavirus
The SARS-CoV-2 virus is filled with proteins that are used to enter human cells. These so-called spike proteins are a tempting target for potential vaccines and treatments.
Like the Moderna vaccine, the Pfizer BioNTech vaccine is based on the virus’s genetic instructions to build the spike protein.
mRNA in an oily dish
The vaccine uses messenger RNA, genetic material that our cells read to make proteins. The molecule – called mRNA for short – is fragile and our natural enzymes would cut it into pieces if injected directly into the body. To protect their vaccine, Pfizer and BioNTech wrap mRNA in oily bubbles made of lipid nanoparticles.
Lipid
Nanoparticles
Surroundings
mRNA
Lipid nanoparticles
surrounding mRNA
Because of their fragility, the mRNA molecules fall apart quickly at room temperature. Pfizer is building special containers with dry ice, thermal sensors, and GPS trackers to ensure vaccines can be transported at -94 degrees Fahrenheit in order to remain viable.
Enter a cell
After injection, the vaccine particles collide with and fuse with cells, releasing mRNA. The cell's molecules read their sequence and form spike proteins. The mRNA from the vaccine is eventually destroyed by the cell and leaves no permanent traces.
Three spines
Proteins combine
spikes
and protein
Fragments
Show
Spike protein
Fragments
Three spines
Proteins combine
spikes
and protein
Fragments
Show
Spike protein
Fragments
Three spines
Proteins combine
spikes
and protein
Fragments
Show
Spike protein
Fragments
Three spines
Proteins combine
spikes
and protein
Fragments
Show
Spike protein
Fragments
Three spines
Proteins combine
spikes
and protein
Fragments
Show
Spike protein
Fragments
Three spines
Proteins combine
spikes
and protein
Fragments
Show
Spike protein
Fragments
Three spines
Proteins combine
spikes
and protein
Fragments
Show
Spike protein
Fragments
Some of the spike proteins form spikes that migrate to the surface of the cell and stick their tips out. The vaccinated cells also break down into fragments some of the proteins that they present on their surface. These protruding spikes and spike protein fragments can then be recognized by the immune system.
Discover the intruder
When a vaccinated cell dies, the debris contains many spike proteins and protein fragments, which can then be taken up by a type of immune cell called an antigen-presenting cell.
Present a
Spike protein
fragment
Present a
Spike protein
fragment
Present a
Spike protein
fragment
The cell presents fragments of the spike protein on its surface. When other cells called helper T cells recognize these fragments, the helper T cells can set off the alarm and help other immune cells fight the infection.
Make antibodies
Other immune cells, called B cells, can encounter the coronavirus spikes and protein fragments on the surface of vaccinated cells. Some of the B cells may be able to bind to the spike proteins. When these B cells are then activated by helper T cells, they start to multiply and pour out antibodies that target the spike protein.
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
surface
Proteins
Matching
surface
Proteins
Matching
surface
Proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Stop the virus
The antibodies can attach to coronavirus spikes, mark the virus for destruction, and prevent infection by preventing the spikes from attaching to other cells.
Kill infected cells
The antigen presenting cells can also activate another type of immune cell called a killer T cell to search for and destroy any coronavirus infected cells that have the spike protein fragments on their surfaces.
Present a
Spike protein
fragment
Beginning
to kill them
infected cell
Present a
Spike protein
fragment
Beginning
to kill them
infected cell
Present a
Spike protein
fragment
Beginning
to kill them
infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Present a
Spike protein
fragment
I'm starting to kill
the infected cell
Memory of the virus
The Pfizer BioNTech vaccine requires two injections 21 days apart to prepare the immune system well enough to fight off the coronavirus. But because the vaccine is so 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
It is possible that the number of antibodies and killer T cells may decrease in the months after vaccination. However, the immune system also contains special cells, so-called storage B cells and storage T cells, which can store information about the coronavirus for years or even decades.
For more information on the vaccine, see Pfizer's Covid Vaccine: 11 Things You Need To Know.
Vaccination schedule
January 2020 BioNTech begins work on a vaccine after Dr. Ugur Sahin, one of the company's founders, is convinced that the coronavirus will spread into a pandemic from China.
March BioNTech and Pfizer agree to work together.
Can The companies are starting a phase 1/2 study with two versions of an mRNA vaccine. One version known as BNT162b2 had fewer side effects.
22nd of July The Trump administration is awarding a $ 1.9 billion contract to ship 100 million doses by December, with an option to purchase an additional 500 million doses if the vaccine is approved by the Food and Drug Administration.
July 27th The companies are starting a phase 2/3 study with 30,000 volunteers in the US and other countries, including Argentina, Brazil and Germany.
12th September Pfizer and BioNTech announce that they will attempt to expand their US study to 44,000 participants.
A vial of the Pfizer BioNTech vaccine.BioNTech via Reuters
November 9th Preliminary data shows the Pfizer vaccine is over 90 percent effective and has no serious side effects. The final data from the study show that the effectiveness rate is 95 percent.
20th November Pfizer applies to the F.D.A.
2. December The UK grants Pfizer and BioNTech an emergency permit, becoming the first western country to grant such approval for a coronavirus vaccine.
10th of December The F.D.A. will meet in an open session to discuss the emergency approval of the Pfizer BioNTech vaccine.
December 31 Pfizer expects to produce up to 50 million doses by the end of the year and up to 1.3 billion doses by 2021. Every vaccinated person needs two doses.
Spring 2021 Pfizer and Moderna vaccines are expected to be widely available in the spring.
Sources: National Center for Information on Biotechnology; Nature; Florian Krammer, Icahn School of Medicine on Mount Sinai.
Comments are closed.