Coronavirus is still spreading at a rapid pace around the globe, the total number of active cases are at 1,990,785, and the number of deaths reached 228,251 figure and still counting. Most countries are still vulnerable to the deadly virus as no genuine vaccine have been developed that can act against the spread of the virus. According to nature’s latest news article “More than 90 vaccines are being developed against SARS-CoV-2 by research teams in companies and universities across the world.” The goal of all vaccines is to create such an immune response that can either stop or kill the virus from the body of an infected person. There are four major types of vaccines being tried against the coronavirus.
Vaccines that are developed using the virus itself, are called virus vaccines. To formulate such vaccines, first the virus needs to be converted into its weakened or inactivated form. Sinovac Biotech company in Beijing has already started to test an inactivated form of SARS-CoV-2 virus in humans.
Weakened virus vaccine: A weak virus is formed by passing it through human/animal cells until its ability to cause disease declines. A company called Codagenix is already working on the weakened SARS-Cov-2 project in collaboration with the Serum Institute of India (SII).
Inactivated virus vaccine: The virus is made uninfectious chemically or thermally. However formulating such vaccines requires the last amounts of infectious viruses.
A virus is genetically engineered so that it can develop coronavirus proteins in the body. There are two subtypes of viral-vector vaccines.
Replicating: The vaccines that tend to replicate itself within the cell are the once called replicating viral-vector vaccines. Ebola vaccine in the best demonstration of such types of vaccines. If the system is already immune to vector then it could decrease the vaccine’s effectiveness.
Non-replicating: US-based Johnsons & Johnsons is working on this project. The viral vectors’ key genes are disabled so that it cannot replicate.
At least 20 teams are working on this approach to formulate an effective vaccine. They aim to use genetic instructions for a coronavirus protein that prompts an immune response. Two kinds of nucleic acid vaccines DNA vaccines and RNA vaccines. Such vaccine are safe and easy to formulate as it requires gene material formation only and not the virus. A process called ‘Electroporation’ is done before injecting to create small pores over cell membranes to ease the insertion of DNA spike gene of coronavirus into the cell.
Earlier the protein-based vaccine has been successfully used against the SARS virus on monkeys to stop infection. Presently 28 research teams are working over this class of vaccine, focusing on the virus’s spike protein or receptor-binding domain. Another class of this type of vaccine is “virus-like particle (VLP)” in which a particle that mimics as a virus is prepared (but it cannot trigger infection due to lack of genes) and inserted into the cell. It results in activating a strong immune response. Although such VLP vaccines are tough to formulate.