Although there are about 90 vaccine prototypes against SARS-CoV-2, which causes the disease COVID-19, being developed in laboratories around the world, they can be classified into several types, depending on their composition. Some of them have already started the clinical trial to verify its effectiveness and safety.
Like all vaccines, these prototypes aim to expose the body to an antigen that will not cause disease, but will elicit an immune response that can block the coronavirus if a person becomes infected.
There are different ways to approach the development of a vaccine. Most of the vaccines that we have are made of the virus or bacteria that we want to fight, inactivated, yes. But currently biotechnology has allowed the development of vaccines made with genetically modified microorganisms, based on DNA or only on one or more proteins of the virus itself. A complete document published by the journal Nature reviews these different types of protovaccines that are currently being tested against the coronavirus. Let’s review below what are its ingredients and how it works.
Vaccines made from viruses
At least seven scientific teams are developing vaccines by inoculating the coronavirus itself into the body, but weakened or inactivated. Many existing vaccines are made this way, such as those against measles and polio, but require extensive safety testing. The Sinovac Biotech laboratory in Beijing has begun testing an inactivated version of SARS-CoV-2 in humans.
Recombinant vector vaccines
About 25 laboratories are working on viral vector vaccines. They are made from ‘parts’ of different viruses, to shape a new microorganism, as if it were a viral ‘Frankenstein’. For example, a virus such as measles can be used, genetically modifying it so that it can produce coronavirus proteins in the body. These viruses are inoculated weakened so that they cannot cause disease.
DNA or RNA vaccines
As Nature publishes, at least 20 teams are trying to use genetic instructions (in the form of DNA or RNA) to shape a coronavirus protein capable of eliciting an immune response. The nucleic acid inserts into human cells, which then produce copies of the virus protein. What most of these vaccines do is encode the spike protein of the virus; it would be like reproducing the orders that the virus gives when it infects the body, but without the need to inoculate the virus itself.
Protein-based vaccines
SARS-CoV-2 has three-dimensional structures in the receptor-binding domain or RBD, which is what allows them to ‘latch on’ and enter a cell: they are the S proteins. Many researchers are working on vaccines that inoculate proteins of the coronavirus directly into the body. Protein fragments or protein layers that mimic the outer layer of the coronavirus can also be used. This type of vaccine has not yet been tested in humans, although it has offered promising results in primates.
More than 70% of the groups leading vaccine research efforts are from private companies.
Manufacturing a vaccine is a long and expensive process. Clinical trials begin with small safety studies in animals and people, followed by much larger trials to determine whether a vaccine elicits an immune response. Researchers are accelerating these steps and hope to have a vaccine ready in 18 months.
Sources:
US Department of Health and Human Services.
‘The race for coronavirus vaccines: a graphical guide’. Nature (2020)
