How Moderna’s Vaccine Works – The New York Times
Moderna, a Massachusetts-based vaccine developer, worked with the National Institutes of Health to develop and test a coronavirus vaccine known as mRNA-1273. A clinical study showed the vaccine had a 94.1 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 Pfizer vaccine, Moderna's vaccine is based on the virus' genetic instructions to make 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. Moderna vaccine requires refrigeration and should be stable for up to six months if shipped and stored at -4 degrees Fahrenheit.
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
Moderna's vaccine requires two injections 28 days apart to keep the immune system activated 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.
An early study found that Moderna's vaccine provided protection for at least three months.
For more information on the vaccine, see Moderna's Covid Vaccine: What You Need To Know.
Vaccination schedule
January 2020 Moderna begins work on a coronavirus vaccine.
March 16 Moderna scientists are the first to use a Covid-19 vaccine in human studies.
April 16 Moderna announces that the US government will allocate $ 483 million to develop and test Moderna's vaccine. Researchers at the National Institutes of Health will oversee much of the research, including clinical trials.
July 27th After initial studies that show promising results, Moderna and the N.I.H. Start with Phase 3 testing on 30,000 US volunteers. A quarter of the participants are 65 years or older.
A nurse prepares a shot of the Moderna vaccine.Hans Pennink / Associated Press
July 28th Moderna notes that the vaccine will protect monkeys from the coronavirus.
August 11th The United States government will grant the company an additional $ 1.5 billion in consideration for 100 million doses if the vaccine is approved by the Food and Drug Administration.
November 16 Moderna announces preliminary data from its phase 3 study. The researchers estimate that the vaccine has an efficacy rate of 94.1 percent, which is well above what the experts expected at the start of the vaccine tests.
30th of November Moderna applies for an emergency permit from the F.D.A.
2. December Moderna is registering a study to test the vaccine on children between 12 and 18 years of age.
December 17th The F.D.A. will meet in an open session to discuss the emergency approval for the Moderna vaccine.
21st December If Moderna gets an emergency clearance, the first injections of its vaccine could begin on December 21st.
December 31 The company expects to produce 20 million cans by the end of this year and up to a billion cans by 2021. Every vaccinated person needs two doses.
Spring 2021 Moderna and Pfizer 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.
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