How Pfizer’s vaccine works – The New York Times

0
28







German company BioNTech has partnered with Pfizer to develop and test a vaccine against the coronavirus known as BNT162b2. A clinical trial has shown that the vaccine has a 95% effectiveness rate in preventing Covid-19.

A piece of the coronavirus

The SARS-CoV-2 virus is studded with proteins that it uses 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 inside an oily shell

The vaccine uses messenger RNA, genetic material that our cells read to make proteins. The molecule – called mRNA – is fragile and would be cut into pieces by our natural enzymes if injected directly into the body. To protect their vaccine, Pfizer and BioNTech wrap mRNA in oily bubbles made up of lipid nanoparticles.






lipids

nanoparticles

surroundings

MRNA

Lipid nanoparticles

Surrounding mRNA


Due to their fragility, mRNA molecules disintegrate rapidly at room temperature. Pfizer builds special containers with dry ice, thermal sensors and GPS trackers to ensure that vaccines can be transported at -94 degrees Fahrenheit to remain viable.

Enter a cell

After the injection, the vaccine particles strike the cells and fuse with them, releasing mRNA. Molecules in the cell read its sequence and build advanced proteins. The vaccine’s mRNA is eventually destroyed by the cell, leaving no permanent traces.






Three points

proteins combine

Spikes

and proteins

fragments

Display

spike protein

fragments

Three points

proteins combine

Spikes

and proteins

fragments

Display

spike protein

fragments

Three points

proteins combine

Spikes

and proteins

fragments

Display

spike protein

fragments

Three points

proteins combine

Spikes

and proteins

fragments

Display

spike protein

fragments

Three points

proteins combine

Spikes

and proteins

fragments

Display

spike protein

fragments

Three points

proteins combine

Spikes

and proteins

fragments

Display

spike protein

fragments

Three points

proteins combine

Spikes

and proteins

fragments

Display

spike protein

fragments


Some of the spike proteins form spikes that migrate to the cell surface and protrude from their ends. Vaccinated cells also break down some of the proteins into fragments, which they present on their surface. These protruding spikes and fragments of spike proteins can then be recognized by the immune system.

Spot 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 has fragments of the spike protein on its surface. When other cells called T helper cells detect these fragments, the helper T cells can raise the alarm and help gather other immune cells to fight infection.

Make antibodies

Other immune cells, called B cells, can strike coronavirus peaks and protein fragments on the surface of vaccinated cells. Some of the B cells may be able to lock onto spike proteins. If these B cells are then activated by helper T cells, they will start to proliferate and release antibodies that target the spike protein.






Corresponding to

surface proteins

Corresponding to

surface proteins

Corresponding to

surface proteins

Corresponding to

surface proteins

Corresponding to

surface proteins

Corresponding to

surface proteins

Corresponding to

surface

protein

Corresponding to

surface

protein

Corresponding to

surface

protein

Corresponding to

surface proteins

Corresponding to

surface proteins

Corresponding to

surface proteins


Stop the virus

Antibodies can cling to peaks in coronavirus, mark the virus for destruction, and prevent infection by preventing the peaks from attaching to other cells.


Kill infected cells

Antigen-presenting cells can also activate another type of immune cell called a killer T cell to find and destroy any cells infected with coronavirus that display the spike protein fragments on their surfaces.






Present a

spike protein

fragment

Start

kill the

infected cell

Present a

spike protein

fragment

Start

kill the

infected cell

Present a

spike protein

fragment

Start

kill the

infected cell

Present a

spike protein

fragment

Start killing

the infected cell

Present a

spike protein

fragment

Start killing

the infected cell

Present a

spike protein

fragment

Start killing

the infected cell

Present a

spike protein

fragment

Start killing

the infected cell

Present a

spike protein

fragment

Start killing

the infected cell

Present a

spike protein

fragment

Start killing

the infected cell

Present a

spike protein

fragment

Start killing

the infected cell

Present a

spike protein

fragment

Start killing

the infected cell

Present a

spike protein

fragment

Start killing

the infected cell


Remember the virus

The Pfizer-BioNTech vaccine requires two injections, spaced 21 days apart, to prime the immune system enough to fight the coronavirus. But because the vaccine is so new, researchers aren’t sure how long its protection might last.






Second dose

21 days later

Second dose

21 days later

Second dose

21 days later


It is possible that in the months following vaccination, the number of antibodies and killer T cells may decrease. But the immune system also contains special cells called memory B cells and memory T cells that could hold information about the coronavirus for years or even decades.

To learn more about the vaccine, see Pfizer’s Covid Vaccine: 11 Things You Need to Know.

Vaccine timeline

January 2020 BioNTech begins work on a vaccine after Dr Ugur Sahin, one of the founders of the company, was convinced the coronavirus would spread from China to a pandemic.

Mars BioNTech and Pfizer agree to collaborate.

Can The companies are launching a phase 1/2 trial of two versions of an mRNA vaccine. One version, known as BNT162b2, had fewer side effects.

22nd of July The Trump administration awards a $ 1.9 billion contract for 100 million doses to be delivered by December, with an option to acquire an additional 500 million doses, if the vaccine is cleared by the Food and Drug Administration.

July 27 The companies are launching a Phase 2/3 trial with 30,000 volunteers in the United States and other countries, including Argentina, Brazil and Germany.

12 sept. Pfizer and BioNTech announce they will seek to expand their US trial to 44,000 participants.



A vial of the Pfizer-BioNTech vaccine.BioNTech, via Reuters

November 9 Preliminary data indicates that the Pfizer vaccine is over 90% effective with no serious side effects. The final data from the trial shows the efficacy rate to be 95%.

November 20 Pfizer seeks emergency use authorization from the FDA

Dec 2 Britain gives emergency vaccine clearance from Pfizer and BioNTech, becoming the first Western country to give such approval to a vaccine against the coronavirus.

Dec 10 The FDA will meet in open session to discuss emergency clearance for the Pfizer-BioNTech vaccine.

Dec 31 Pfizer plans to produce up to 50 million doses by the end of the year and up to 1.3 billion doses by 2021. Each person vaccinated will need two doses.

Spring 2021 The vaccines from Pfizer and Moderna are expected to reach wide distribution in the spring.


Sources: National Center for Biotechnology Information; Nature; Florian Krammer, Icahn School of Medicine at Mount Sinai.

Coronavirus monitoring


(vitag.Init = window.vitag.Init || []).push(function () { viAPItag.display(“vi_1088641796”) })

LEAVE A REPLY

Please enter your comment!
Please enter your name here