How Moderna’s vaccine works – The New York Times

Moderna, a Massachusetts-based vaccine developer, has partnered with the National Institutes of Health to develop and test a vaccine against the coronavirus known as MRNA-1273. A clinical trial has shown that the vaccine has an efficacy rate of 94.1% 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 Pfizer vaccine, Moderna’s 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.

Due to their fragility, mRNA molecules disintegrate rapidly at room temperature. Moderna’s vaccine will need to be refrigerated and should be stable for up to six months when shipped and stored at -4 degrees Fahrenheit.

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.

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.

The cell has fragments of the spike protein on its surface. When other cells called helper T cells detect these fragments, the helper T cells can sound 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.

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 search for and destroy any cells infected with coronavirus that present the spike protein fragments on their surfaces.

Remember the virus

Moderna’s vaccine requires two injections, 28 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.

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.

An initial study found that Moderna’s vaccine provides protection for at least three months.

To learn more about the vaccine, see Moderna’s Covid Vaccine: What you need to know.

Vaccine timeline

January 2020 Moderna begins work on a vaccine against the coronavirus.

March 16 Moderna scientists are the first to put a Covid-19 vaccine in human trials.

April 16 Moderna announces that the United States government will provide $ 483 million to support the design and testing of Moderna’s vaccine. Researchers at the National Institutes of Health will oversee much of the research, including clinical trials.

July 27 After initial studies show promising results, Moderna and the NIH begin phase 3 testing of 30,000 volunteers across the United States. A quarter of the participants are 65 years or older.

July 28 Moderna finds that the vaccine protects monkeys from coronavirus.

Aug 11 The US government is giving the company an additional $ 1.5 billion in exchange for 100 million doses, if the vaccine is cleared by the Food and Drug Administration.

November 16 Moderna announces preliminary data from its phase 3 trial. Researchers estimate that the vaccine has an efficacy rate of 94.1%, much higher than what experts had expected at the start of vaccine testing.

November 30 Moderna seeks emergency use authorization from the FDA

Dec 2 Moderna is registering a trial to test the vaccine on children between 12 and 18 years old.

Dec 17 The FDA will meet in open session to discuss emergency clearance for the Moderna vaccine.

Dec 21 If Moderna receives an emergency use authorization, the first injections of its vaccine could begin on December 21.

Dec 31 The company plans to produce 20 million doses by the end of this year and up to one billion doses by 2021. Each person vaccinated will need two doses.

Spring 2021 Moderna and Pfizer’s vaccines are expected to reach widespread distribution in the spring.

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

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