What are the new Covid-19 vaccine platforms?

So far, about 63% of adult Indians have received both the doses of Covid-19 vaccines. And more than 90% have got at least one dose.

India has majorly relied on the viral vector vaccine Covishield for its vaccination drive. Over 88% of the doses given out so far have been of Covishield, the Oxford-AstraZeneca vaccine manufactured locally under licence by the Serum Institute of India. Covaxin accounted for just a fraction.

The two new vaccines approved for emergency use last month are Serum Institute of India’s Covovax and Biological E’s Corbevax.

With last month’s approval, the country now has eight vaccines in its kitty. Apart from the four discussed earlier, the remaining four are -- Sputnik V, ZyCoV-D, Moderna and Johnson and Johnson.

Covishield uses the viral vector technology, while Pfizer and Moderna vaccines are based on messenger RNA or mRNA. Vaccination in western countries has been led by mRNA vaccines. Let us see what all vaccine platforms we have -

Broadly, there are four types of platforms which are used in making the vaccine worldwide. They are RNA, viral vector, inactivated virus and protein-based platforms.

Here, we are discussing the two most popular platforms on which most vaccines have been developed. They are viral vector and mRNA platforms. Let us understand the difference between the two, starting with the viral vector vaccine.

But before that, let us understand that coronaviruses are named so because of the crown-like spikes on their surface, called spike protein or S protein. These spike proteins are the most used target for vaccines. 

Viral Vector vaccines

Now, let us understand what a viral vector vaccine is. It uses a harmless version of a different virus, called a “vector,” to deliver information to the body that helps it protect you.

Genetic material from the target virus, in this case the Covid-19 virus, is placed inside the viral vector.  Once it enters a person’s cells, it gives the cells instructions to make harmless copies of the spike protein.

As the cells display the spike protein on their surfaces, the immune system starts producing antibodies and a type of white blood cells to fight off what it believes is an infection. If a person is later infected from the Covid -19 virus, these antibodies are already there to fight them.

The vaccine doesn’t contain the Covid -19 virus or the viral vector virus. Moreover, it does not change the DNA in any way. Covishield, Oxford-AstraZeneca, Janssen (J&J) and Sputnik V and Sputnik Lite use this platform.

mRNA vaccine

While mRNA vaccine uses genetically engineered messenger RNA created in a laboratory to teach our cells how to make a harmless variant of the spike protein that is found on the surface of Covid-19 virus. The presence of a foreign protein triggers a normal immune response, which produces antibodies that protects us from infection if the real virus enters the body.

The vaccine is made of mRNA wrapped in a coating called the lipid nano-particle that makes the delivery easy and keeps the body from damaging it.

And just like the viral vector vaccine, mRNA vaccine does not contain any virus, so it cannot give you an infection. After the mRNA delivers the instructions, our cells break it down immediately. Pfizer-BioNTech and Moderna use this technology to fight off the virus. 

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