COVID-19 vaccines – what do we know about them?

COVID-19 vaccines - what do we know about them?

Three vaccines for coronavirus produced by Pfizer/BioNTech, Moderna and AstraZeneca are currently approved. But it doesn’t stop there – there are more than 165 preparations to protect against COVID-19 in clinical trials around the world. What is the process of testing vaccines?

SARS-CoV-2 coronavirus vaccines.

Since the start of the pandemic, all the while pharmaceutical companies have been racing to develop an effective and safe vaccine against the coronavirus. So far, preparations from three companies – the combined forces of Pfizer and BioNTech, Moderna and AstraZeneca – have been approved for use.

The efficacy of the first two vaccines is estimated at 95% provided two doses are taken. AstraZeneca guarantees 60% efficacy in protecting against the disease and almost 100% in protecting against severe disease and complications. More than 165 other brands are working on further formulations, some of which are already being tested on humans.

Read: COVID-19 is a thing of the past? World Health Organization experts have decided.

How are the vaccines for Covid divided?

Coronavirus vaccines can be divided into genetic, vector-based, SARS-CoV-2 protein-based and whole virus-based. Genetic vaccines include Pfizer/BioNTech and Moderna formulations. They contain synthetic mRNA encapsulated in a lipid sheath that triggers an immune response. This allows the body to defend itself quickly and effectively if it comes into contact with an active virus. Both types of preparations should be stored at low temperature – Pfizer/BioNTech at -70 degrees Celsius for up to six months, and Moderna, due to its majority of stabilizer content, at -25 to -15 degrees Celsius also for up to six months. Vaccines using mRNA are also being developed by Imperial College London in collaboration with Morningside Ventures, Arcturus Therapeutics at Duke-NUS Medical School in Singapore, and Sanofi with Translate Bio.

Vector vaccines use fragments of other viruses to induce an immune response against COVID-19. AstraZeneca’s formulation based on chimpanzee adenovirus in collaboration with Oxford University is such a vaccine. A vector vaccine is also being attempted by CanSino Biologics with the Chinese Institute of Biology of the Military Academy of Medical Sciences. The formulation is to be based on adenovirus Ad5. Johnson&Johnson’s vaccines with Beth Israel Deconess Medical Center, Novartis and Merck’s IAVI, and Vaxart’s Themis Biosence are expected to work similarly.

Vaccines based on the SARS-CoV-2 protein use either the coronavirus protein or a fragment of it to generate an immune response. Such preparations are being made by Anhiu Zhfei Longcom in collaboration with the Chinese Academy of Medical Sciences, US-based Novavax, Clover Biopramaceuticals of GSK and Dynavax and Sanofi. Some of the companies claim to be able to produce up to several hundred million doses per year.

What remains are preparations based on the whole virus – either an inactivated or weakened version of SARS-CoV-2 is used to produce them. Work on the vaccine is being carried out by China’s Sinopharm, Sinovac Biotech, as well as India’s Bharat Biotech from the Indian Council of Medical Reaserch and the National Institute of Vitology. The last group is working on an inactivated rabies virus.

What progress is being made on the COVID-19 vaccine?

A vaccine against COVID-19 is already available, but larger-scale production will be needed to get the vaccine to as many people as possible. The more formulations that are approved for use, the sooner anyone who wants to be vaccinated will have the opportunity to do so. Some of the vaccines listed are in phase II or III trials, which gives hope for a short time to reach the market. In practice, clinical trials are divided into three phases – Phase I is safety and dosage testing, Phase II is extended safety trials, and Phase III is large-scale efficacy testing. After this, the formulation receives approval for limited use and only at the end is it approved for full use.

In Phase I, the vaccine is administered to humans – usually a group of 20-100 volunteers. In Phase II, 100 to 300 people are tested, and in Phase III, for which only the best quality preparations are approved, testing is done on a group of 10,000 volunteers or more.

Which vaccines will be used in the coming months? The most advanced clinical trials are being conducted by CurVac (mRNA vaccine), Johnson&Johnson (vector vaccine), Novavax and Sanofi-GSK (recombinant, protein-based vaccines).


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