There are more vaccine candidates in the COVID-19 pipeline at the same time than ever before as an infectious disease. All of them are trying to achieve the same thing. It is immune to the virus, and some can also stop the infection.
Four major types of COVID-19 vaccine
There are four categories of vaccines in clinical trials—some attempt to smuggle antigens into the body, while others use cells to produce viral antigens.
Many traditional vaccines use the actual virus to provoke an immune response. There are two main approaches. Live attenuated vaccines use an attenuated virus that can replicate without causing disease. Inactivated vaccines use a virus whose genetic material has been destroyed not to replicate, but it can still provoke an immune response. Inactivated virus vaccines can be given to people with weakened immunity but require refrigeration, which often requires careful refrigeration, making them more challenging to use in low-income countries. It may be. For example, Bharat Biotech’s COVAXIN is an all-virus-based vaccine with 76% efficacy.
Subunit vaccines use a portion of the pathogen (often a protein fragment) to provoke an immune response. Doing so minimizes the risk of side effects, but it can also weaken the immune response. As a result, adjuvants are often needed to boost the immune response. Several more advanced Covid-19 vaccines that use this approach include Novavax and the Chinese Academy of Sciences.
Nucleic acid vaccines use genetic material, either RNA or DNA, to provide instructions for making antigens in cells. For COVID-19, this is usually a viral spike protein. When this genetic material enters human cells, it uses the cell’s protein factories to produce antigens that provoke an immune response. The advantage of these vaccines is that they are easy to manufacture and inexpensive. The immune response should be strong because the antigen is produced in large quantities in our cells. However, so far, the drawback is that there is no DNA or RNA vaccine. Since they are licensed for human use, they can pose additional hurdles for regulatory approval. In addition, RNA vaccines need to be stored at cryogenic temperatures below -70 ° C, which can be a challenge for countries without special refrigeration equipment, especially low- and middle-income countries. Two Covid-19 RNA vaccines have been approved for use: Pfizer-BioNTech and Moderna have reported high levels of vaccine efficacy of approximately 95%.
Viral vector vaccines also work by giving cells genetic instructions to make antigens. However, unlike nucleic acid vaccines, they use a harmless virus different from what the vaccine targets to convey these instructions to cells. One of the most commonly used viruses as a vector is the adenovirus, which causes the common cold. Similar to nucleic acid vaccines, our cellular mechanisms are hijacked to provoke an immune response, producing antigens from those instructions. Viral vector vaccines can mimic natural viral infections and should elicit a robust immune response. However, because many people may already be infected with the vector virus, some may be immune, and the vaccine may be less effective. Oxford-AstraZeneca or covidshield is the first viral vector vaccine approved for Covid-19. It is about 78% efficient.