How the Novavax Covid-19 vaccine works

Maryland-based company Novavax has developed a protein-based coronavirus vaccine NVX-CoV2373. The vaccine produced remarkably high levels of antibodies in early clinical trials. In September, the vaccine entered a phase 3 clinical trial in the United Kingdom and another in the United States at the end of December. These tests will show if the vaccine is safe and effective.

Coronavirus proteins

The SARS-CoV-2 virus is littered with proteins that it uses to enter human cells. These so-called vein proteins are an attractive target for potential vaccines and treatments.

The Novavax vaccine works by teaching the immune system to form antibodies against the protein.

Growing vein proteins

To create their vaccine, Novavax researchers started using a modified spike gene. They inserted the gene into another virus, called a baculovirus, and allowed it to infect insect cells. The infected cells produced peak proteins that spontaneously joined together to form nails, such as on the surface of the coronavirus.

A similar method of culturing and harvesting viral proteins is already being used to make licensed vaccines for diseases, including influenza and HPV.

Building nanoparticles

The researchers harvested the vein proteins from the insect cells and assembled them into nanoparticles. While the nanoparticles mimicked the molecular structure of the coronavirus, they could not replicate or cause Covid-19.

The presentation of the Spike

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

See the intruder

Immune cells called antigen-presenting cells encounter and take up the vaccine nanoparticles.

An antigen-presenting cell tears the vein proteins apart and displays some of their fragments on the surface. A so-called helper T cell can detect the fragments. When a fragment fits into one of its surface proteins, the T cell is activated. Now it can recruit other immune cells to respond to the vaccine.

Make antibodies

Another type of immune cell, called a B cell, can also encounter the vaccine nanoparticles. B cells have surface proteins in a wide variety of forms, and some may have the right shape to adhere to a vein protein. If a B cell gets stuck, it can retrieve the vaccine particle and leave broken protein fragments on the surface.

When a helper T cell activated against the vein protein sounds to one of these fragments, it activates the B cell. Now the B cell multiplies and releases antibodies that have the same shape as the surface proteins.

Stop the Coronavirus

If people who are vaccinated are later exposed to the coronavirus, their antibodies can get stuck on the vein proteins. The coronavirus cannot enter cells, and the infection is blocked.

Killing infected cells

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

Remember the virus

The Novavax vaccine will be more easily distributed and stored than the vaccines from Pfizer-BioNTech and Moderna. While the vaccines need to be frozen, NVX-CoV2373 can remain stable in the refrigerator for up to three months. But if the vaccine does prove to be effective, scientists will not know for sure how long it will be protected.

When it works like 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 store information about the coronavirus for years or even decades, allowing for a rapid counterattack in response to a new infection.

Vaccination timeline

January 2020 Novavax is starting work on a coronavirus vaccine.

May Novavax is launching clinical trials for their vaccine.

July The US government is allocating $ 1.6 billion to Novavax to support the clinical trials and manufacture of the vaccine.

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

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

December 28 Novavax launches a Phase 3 trial with 30,000 people in the United States. The trial was delayed due to difficulties in producing the doses required for the study.

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

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

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