How do the different coronavirus vaccines work? Here a look

Published in 25 November, 2020

(CNN) – There’s good news about coronavirus vaccines. At least three of the experimental vaccines show remarkable efficacy, at least according to information published by the manufacturers in press releases.

Global vaccine giant AstraZeneca reports that its vaccine prevented coronavirus infection 62% of the time when people received two doses one month apart. But in a subset of volunteers who received a half dose followed by a full dose a month later, the vaccine appeared to be 90% effective.

That has an average efficiency of 70%. Vaccines made by Pfizer Inc and the biotech company Moderna appear to protect against symptomatic infection 95% of the time.

The Pfizer and Moderna vaccines use very similar technology, while AstraZeneca uses a different approach. They are among the six vaccines that receive some form of support from the federal government in the United States and dozens in development around the world.

Here’s a look at the technology behind some of the candidates that are more advanced in development, mostly in Phase 3 clinical trials, the last step before seeking the go-ahead from the US Food and Drug Administration. (FDA) and other regulators around the world.

Pfizer and BioNTech

Pfizer and its German-based partner BioNTech are using a new approach to making vaccines that uses messenger RNA, or mRNA.

This design was chosen for a pandemic vaccine years ago because it is one that lends itself to a rapid response. All that is needed is the genetic sequence of the virus causing the pandemic. Vaccine manufacturers don’t even need the virus itself, just the sequence.

In this case, the BioNTech researchers used a small piece of genetic material that encodes a fragment of the spike protein, the structure that adorns the surface of the coronavirus, giving it that studded appearance.

LEE: The scientists who developed the Pfizer / BioNTech vaccine against covid-19 are a powerful Turkish-German couple

Messenger RNA is a single strand of the genetic code that cells can “read” and use to make a protein. In the case of this vaccine, the mRNA instructs the cells of the body to produce the particular part of the spike protein of the virus. The immune system then sees it, recognizes it as foreign, and is ready to attack when an actual infection occurs.

The mRNA is very fragile, so it is enveloped in lipid nanoparticles, a layer of a buttery substance that can melt at room temperature. That is why Pfizer’s vaccine must be kept at ultra-cold temperatures of approximately -75 degrees Celsius. That means that special equipment is needed to transport and store this vaccine.

Modern

Moderna’s vaccine is also based on mRNA. “The mRNA is like software for the cell,” Moderna said on his website.

And like the Pfizer / BioNTech vaccine, it codes for cells to make a portion of the spike protein. That was a careful choice: the scientists had to choose a part of the virus that they thought would not mutate or change much over time. The virus uses the spike protein to grasp the cells it attacks, and the structure appears to remain stable generation after generation of viral replication.

Moderna has created a different formulation for lipid nanoparticles to protect the mRNA of its vaccine. These formulations are corporate secrets, but Moderna believes their approach is better, saying their vaccine can be shipped at -20 degrees Celsius and can be stable for 30 days between 2 degrees and 8 degrees Celsius, the temperature of a standard household refrigerator.

LOOK : How is Pfizer’s covid-19 vaccine going to be distributed if it has to be frozen at -70 degrees Celsius?

AstraZeneca

The AstraZeneca vaccine, made with a team at the University of Oxford in Great Britain, is called a vector vaccine. It uses a common cold virus called adenovirus to transport the coronavirus spike protein into cells.

It also aims to make people’s bodies, in essence, produce their own vaccines by producing small copies of spike proteins, but the method of administration is different. This adenovirus infects chimpanzees but does not make people sick. It was engineered to not replicate, then genetically engineered to inject cells with the DNA that encodes the full-length coronavirus spike protein.

It is a cheaper way to make vaccines, but slower than using RNA. The company is committed to making its vaccine available at low cost in countries around the world. The vaccine can be stable for six months at standard refrigerator temperatures, the company said.

READ : AstraZeneca vaccine data raise doubts among experts

Janssen Pharmaceuticals, Johnson & Johnson Vaccine Division

The Janssen coronavirus vaccine is a recombinant vector vaccine. Like AstraZeneca’s, it uses an adenovirus, but it infects humans. It is a genetically modified version of adenovirus 26, which can cause the common cold, but has been disabled by genetic modification. It also provides the genetic instructions for producing spike proteins.

This is a vaccine that has been tested in the market before. The adenovirus 26 vector was used to make the company’s Ebola vaccine, which obtained marketing authorization from the European Commission in July.

It’s a single-shot vaccine, but earlier this month Johnson & Johnson started a two-dose phase 3 trial in Britain, because there is some evidence that two doses provide better protection. Volunteers will receive two injections, 57 days apart, or placebos.

Novavax

Maryland-based biotechnology company Novavax specializes in “subunit protein” vaccines. They use virus-like nanoparticles as a base and coat them with genetically modified pieces of the coronavirus spike protein.

This is also a tried and true vaccine approach. One hepatitis B vaccine given to newborns is a protein subunit vaccine, as is the human papillomavirus or HPV vaccine and FluBlok, the influenza vaccine from Sanofi.

Novavax uses an insect virus called baculovirus to carry the protein from the coronavirus beak to the moth’s cells, which then produce the protein. This is harvested and mixed with an adjuvant, an immune booster, based on saponin, found in soap bark trees.

Sanofi and GlaxoSmithKline

This is also a protein subunit vaccine, using Sanofi’s FluBlok technology with a GlaxoSmithKline adjuvant. It also uses a baculovirus to produce small chunks of spike protein.

Sinovac and Sinopharm

CoronaVac from the Chinese company Sinovac uses an inactivated virus, one of the oldest methods of vaccinating people. Whole batches of coronavirus are grown, ‘killed’, and then turned into vaccines. Also, the Sinopharm vaccine in an inactivated virus.

Sputnik

Russia’s Sputnik coronavirus vaccine is an adenoviral vector vaccine. It uses a common cold virus called adenovirus 5 to transport the spike protein’s genetic material to the body.

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