Akash Mitra


Covid vaccines and their comparison

India along with a lot of other countries are successful in developing numerous types of vaccines against Covid-19 disease. All the vaccines have similarities and dissimilarities about which I am going to try and throw some light in this article.

πŸ’‰ Types of vaccines

Whole virus vaccine

There are two main approaches for creating whole virus vaccines –

Live attenuated vaccine – Uses a weakened virus that still hasn’t lost the ability to replicate. It can’t cause illness because we remove the virulent factors.

Inactivated vaccine – These vaccines have viruses with destroyed genetic material. Hence, they cannot replicate but can still trigger an immune response.

Although, both forms of vaccines use well established technologies for regulation, but people with weak immune systems can fall victim to the effect of the live attenuated ones. Moreover, they require careful cold storage which is a challenge for countries with low resources.

Protein subunit vaccine

These do not use the whole pathogen, but, some fragments, generally, proteins which can trigger the immune response. This reduces the risk of side effects at the cost of a weaker immune response. Through technologies, we provide adjuvants, to help boost the immune response. Hepatitis B vaccine is an example of protein subunit vaccine.

Nucleic acid vaccine

These type of vaccines use genetic material (DNA or RNA) to instruct cells to make the antigen required. The genetic material travels into the cells where it uses the cell’s machinery to synthesize the proteins/antigens that can trigger the immune response. The advantages of this type of vaccines are they are cheap and easy to make. Since the synthesis of the antigenic protein occurs inside our own cells in huge amount, the immune response is also strong. The disadvantage is the requirement of the cold storage conditions (-70 degree Celsius or below).

Viral vector

This type uses a harmless virus which is different from the one the vaccine is targeting. The virus is a vehicle to take the nucleic acid and deliver it into our cells. Like nucleic acid vaccines, they hijack the cellular machinery and synthesize the antigen required. Viral vectors can mimic natural viral infection and should therefore trigger a strong immune response. The downside is, people already exposed to the vector virus might already develop antibodies against it.

πŸ”¬ Covid-19 vaccines in India

Covishield (viral vector Covid vaccine)

Developed by AstraZeneca in collaboration with Oxford University and manufactured by Serum Institute of India, Pune, it is one of the most widely used vaccine in India. It is a viral vector vaccine which uses a common cold adenovirus from chimpanzees. The interval between the first and the second doses of this vaccine is 4-8 weeks as prescribed by the Government of India. It has got an efficacy rate of 70% as per Drugs Controller General of India. Covishield works effectively against the Uk strain as well

Covid vaccine Covishield

Covaxin (killed Covid vaccine)

Bharat Biotech developed this indigenous vaccine. It is an inactivated vaccine which has an efficacy between 70%-90%. Covaxin uses a killed coronavirus which prompts the immune system to make antibodies. It requires two doses with a gap of 28 days in between.

Covid vaccine Covaxin

Sputnik V (viral vector Covid vaccine)

It is a Russian vaccine and Indian Government recently authorized its use in the country. Gamaleya research Institute of Epidemiology and Microbiology is responsible for developing the vaccine. This is also a vector vaccine like covishield which provides around 92% protection against coronavirus. Moreover, is a great option against the mutations of the virus. This is because it uses two totally different shots. The theoretical efficacy of sputnik V is the highest.

Covid vaccine Sputnik V

πŸ™‹β€β™‚οΈ End note

It doesn’t matter what vaccine we get jabbed with because all three have shown promising results. And hence, we should get vaccinated at the very first instance possible. All have more or less the same results irrespective of their varying efficacies.

πŸ“– Recommended reading

  1. Being a Microbiology student
  2. Bioinformatics – A double-edged sword