How the Novavax Covid-19 vaccine works

Maryland-based company Novavax developed a protein-based coronavirus vaccine called NVX-CoV2373. The vaccine produced surprisingly high levels of antibodies in the first clinical trials. In September, the vaccine entered a Phase 3 clinical trial in the United Kingdom and another in the United States in late December. These tests will show whether the vaccine is safe and effective.

Coronavirus Proteins

The SARS-CoV-2 virus is full of proteins that it uses to enter human cells. These proteins called pico are a tempting target for vaccines and potential treatments.

The Novavax vaccine teaches the immune system to make antibodies to the protein spike.

Growing Spike Proteins

To create their vaccine, Novavax researchers started with a modified spike gene. They inserted the gene into a different virus, called baculovirus, and allowed it to infect insect cells. The infected cells produced spike proteins that joined spontaneously to form spikes, just as they do on the surface of the coronavirus.

A similar method of growing and collecting virus proteins is already used to make licensed vaccines for diseases, including influenza and HPV.

Building Nanoparticles

The researchers collected the proteins from the peak of the insect cells and assembled them in nanoparticles. Although nanoparticles mimic the molecular structure of the coronavirus, they cannot replicate or cause Covid-19.

Presenting the peak

The vaccine is injected into the muscles of the arm. Each injection includes many nanoparticles of thorns, along with a compound extracted from the soap bark tree. The compound attracts immune cells to the injection site and makes them respond more strongly to nanoparticles.

Spotting the Intruder

Immune cells called antigen-presenting cells find the vaccine’s nanoparticles and absorb them.

An antigen-presenting cell separates proteins from the peak and displays some of their fragments on their surface. A so-called auxiliary T cell can detect the fragments. If a fragment fits into one of its surface proteins, the T cell is activated. Now he can recruit other immune cells to respond to the vaccine.

Making Antibodies

Another type of immune cell, called a B cell, can also find the vaccine’s nanoparticles. B cells have surface proteins in a wide variety of shapes, and some may have the right shape to attach to a peak protein. If a B cell gets stuck, it can pull the vaccine particle in and have protein fragments on its surface.

If an auxiliary T cell activated against the spike protein clings to one of these fragments, it activates the B cell. Now, the B cell proliferates and releases antibodies that have the same shape as the proteins on its surface.

Stopping the Coronavirus

If vaccinated people are subsequently exposed to the coronavirus, their antibodies can attach to the peak proteins. The coronavirus cannot enter the cells and the infection is blocked.

Killing infected cells

The Novavax vaccine can also trigger another type of protection, destroying infected cells. When a coronavirus invades, infected cells place fragments of its spike protein on its surface. Antigen-presenting cells can activate a type of immune cell called a killer T cell. It can recognize coronavirus-infected cells and destroy them before they have a chance to produce new viruses.

Remembering the virus

The Novavax vaccine would be easier to distribute and store than the vaccines from Pfizer-BioNTech and Moderna. Although these vaccines must be kept frozen, NVX-CoV2373 can remain stable for up to three months in the refrigerator. But if the vaccine is effective, scientists will not be sure for how long it provides protection.

If it functions as protein-based vaccines for other diseases, it can create a group of special cells called memory B cells and memory T cells. These cells will retain information about the coronavirus for years or even decades, allowing for a rapid counterattack in response to a new infection.

Vaccines Timeline

January 2020 Novavax starts work on a vaccine against coronavirus.

May Novavax launches clinical trials for its vaccine.

July The US government grants Novavax $ 1.6 billion to support clinical trials and vaccine manufacturing.

August Novavax launched a Phase 2 test on 2,900 people in South Africa.

September Novavax launches a Phase 3 test with up to 15,000 volunteers in the UK. The test is expected to show results in early 2021.

December 28 Novavax launches a Phase 3 test with 30,000 people in the United States. The trial was postponed due to problems with making the doses required for the study.

2021 If its clinical trials are successful, Novavax expects to deliver 100 million doses for use in the United States in 2021.

Sources: National Center for Biotechnology Information; Nature Reviews Immunology; Science; Maria Elena Bottazzi, Baylor College of Medicine.

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