Covid-19 vaccines: here’s how they work

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

This equates to an average efficiency of 70%. Vaccines manufactured by Pfizer Inc and biotechnology company Moderna appear to protect 95% of the time against symptomatic infections.

The Pfizer and Moderna vaccines use very similar technology, while AstraZeneca uses a different approach. They are among six vaccines with some sort 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 most advanced candidates in development – primarily in Phase 3 clinical trials, the last step before seeking the green light from the U.S. Food and Drug Administration and other agencies. regulations around the world.

Pfizer and BioNTech

Pfizer and its Germany-based partner BioNTech are using a new approach to make vaccines that use messenger RNA or mRNA.

This design was chosen for a pandemic vaccine years ago because it lends itself to rapid turnover. All it takes is the genetic sequence of the virus that caused the pandemic. Vaccine makers don’t even need the virus itself – just the sequence.

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

Messenger RNA is a single strand of genetic code that cells can “read” and use to make a protein. In the case of this vaccine, the mRNA instructs cells in the body to make the particular piece of the virus spike protein. Then the immune system sees it, recognizes it as a stranger, and is ready to attack if there is a real infection.

MRNA is very fragile, so it’s enclosed in lipid nanoparticles – a coating of a buttered substance that can melt at room temperature. This is why Pfizer’s vaccine should be stored at ultra-cold temperatures of about minus 100 degrees F (minus 75 degrees C). This means that special equipment is needed to transport and store this vaccine.

Modern

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

And like the Pfizer / BioNTech vaccine, it codes for cells to make a piece of the spike protein. It was a prudent choice – scientists had to choose a piece of the virus that they believed wouldn’t mutate or change much over time. The virus uses the spike protein to attack the cells it attacks and the structure appears to remain stable from generation to generation of viral replication.

Moderna has developed a different formulation for lipid nanoparticles in order to protect the mRNA of its vaccine. These formulations are company secrets, but Moderna thinks their approach is better and said their vaccine can be shipped at minus 20 degrees C (minus 4 degrees F) and can be kept stable for 30 days between 2 degrees and 8. degrees C (36 to 46F). ), the temperature of a standard household refrigerator.

AstraZeneca

AstraZeneca’s vaccine, made with a team from the UK University of Oxford, is called a vector vaccine. It uses a cold virus called adenovirus to transport the coronavirus spike protein into cells.

It also aims to make people’s bodies essentially produce their own vaccines by producing small copies of advanced 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 DNA encoding the full length coronavirus spike protein.

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

AstraZeneca's Oxford coronavirus vaccine averages 70% effective, data shows without any safety concerns

The vaccine arm of Johnson & Johnson Janssen Pharmaceuticals

The Janssen coronavirus vaccine is a recombinant vector vaccine. Like AstraZeneca, it uses an adenovirus, but this one infects humans. It’s a genetically modified version of adenovirus 26, which can cause the common cold, but gene tinkering has turned it off. It also provides the genetic instructions for making advanced proteins.

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

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

A week after the Covid-19 vaccine trial was paused, Johnson & amp; Johnson and the FDA did not reveal critical details

Novavax

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

It is also a proven vaccine approach. A hepatitis B vaccine given to newborns is a protein subunit vaccine, just like the human papillomavirus or HPV vaccine and FluBlok, the influenza vaccine from Sanofi.

Novavax uses an insect virus called baculovirus to get the coronavirus spike protein into butterfly cells, which then produce the protein. This is harvested and mixed with an adjuvant – an immune booster – made from saponin, found in soap bark trees.

Sanofi and GlaxoSmithKline

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

Nearly one million people have received experimental vaccine against Chinese coronavirus, pharmaceutical giant says

Sinovac and Sinopharm

CoronaVac from Chinese company Sinovac uses an inactivated virus – one of the oldest methods of vaccinating people. Whole batches of coronavirus are grown, “killed” and then made into a vaccine. Likewise, the Sinopharm vaccine in an inactivated virus.

Sputnik

The Russian vaccine against the Sputnik coronavirus is an adenoviral vector vaccine. It uses a cold virus called adenovirus 5 to carry the genetic material for the spike protein around the body.

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