Keeping with the theme of the "new normal", and in light of the recent vaccination drives in
the country, we sat down with Professor Manidipa Banerjee of the Kusuma School of Biological Sciences, IIT Delhi, to shed some light on the Covid vaccines and their mechanisms.
Types of Vaccines
How exactly do vaccines work? Essentially, there are four main types of vaccines:
Inactivated - The virus is cultured in the lab and then inactivated, as in the harmfulness (virulence) is reduced/destroyed completely using either heat or chemicals. Covaxin is an example of such a vaccine.
Subunit virus - An antigen is a substance (usually a protein) that triggers an immune response in the host. In this kind of vaccine, the predominant antigen is isolated and used. An example antigen is the protein coat of the virus.
Viral vector - A harmless virus is used as the base, and a protein is attached to it. For example, Covishield uses adenovirus as the vector, with the spike protein of SARS-CoV-2 attached to it.
mRNA/DNA - This gets inside our cells, teaching them how to make a protein to trigger an immune response in the body. (Zydus Cadila is developing a DNA Vaccine)
Irrespective of the kind of vaccine, though, they all go through various stages of testing, on both animals and on human volunteers of all ages, ethnicities, sex, etc. Thus, all vaccines that are available right now have gone through multiple tests and are safe to take.
One of the biggest buzzwords we hear around vaccines right now is "efficacy", especially in the context of multiple vaccines. The efficacy of a vaccine measures its ability to generate a sufficiently neutralising antibody response. An antibody response is produced by the host when it encounters an antigen. This response is said to be "neutralising" if the antibodies produced by the host are able to effectively counteract the pathogen in question. Efficacy attempts to measure how a person might respond to the actual virus. However, it may not be accurate on an individual level. It may also vary for different variants.
Delta Variant and Mutations
The news of the Delta variant has sparked a few concerns about the danger of a more deadly pandemic resurfacing. Variations in viral strains are prevalent, and they might spread at a fast pace. However, as Professor Banerjee explained, there are low chances of a mutant strain immune to the current vaccines spreading.
Let's take the Delta variant as an example. This variant has higher transmissibility than others. Due to the mutation, the protection provided by antibodies is lower (almost 6x). However, despite this, the chances of someone vaccinated to contract the Delta variant and get extremely sick or die are significantly less. This is possible because vaccines elicit a broad immune response involving a range of antibodies and cells called T-cells, and the T-cell response is not affected by the Delta variant. Take Israel. They were 98% vaccinated with the Pfizer vaccine when they recently had to face the Delta variant. However, when we look at the data of people who had to be hospitalised, they were mainly those with a weak immune system, be it due to their age, pre-existing medical conditions or having to take immunosuppressant drugs.
There have been talks of the possible need for "booster doses", which may be required to supplement the action of the initial doses. The Covid-19 virus was first detected around late 2019-early 2020. By the end of 2020, we already had vaccines in deployment. This is nothing short of a medical miracle! However, since these vaccines were developed in such a short time, there are still some things that we don't know, such as how long the immunity provided by them will last. We are still figuring this out in the field, and it depends on the individual vaccine and the mutations the virus develops. Thus, there is a chance that immunity may reduce over time. A booster dose is essentially an additional dose of the vaccine, somewhat similar to the second dose that most of us have received. Data such as the type of vaccine and how fast the immunity decreases will determine the need for a booster dose. For example, there is talk that the Johnson & Johnson vaccine (which was a one-dose vaccine) may require a booster dose.
Side effects caused by the vaccines usually indicate that the recipient's immune system is mounting a response. This is a positive thing in the case of most mild side effects, such as dizziness, muscle soreness, fever, etc. However, a tiny percentage of people may experience more severe side effects, such as blood clots, as your medical personnel will tell you when you take the vaccine. Clearly, fear of rare extreme side effects should not be a reason to refrain from vaccination.
Research at IIT-D and Vaccine Development
With regards to the research at IIT Delhi pertaining to the Covid pandemic, Prof. Banerjee says, "My lab is currently working on designing virus-like particles as vaccine candidates against nCov-19. What we're essentially doing is working with relatively harmless viruses to make virus-like particles. These contain the structural proteins but not the genomes of nCov-19. We then conduct antigenic and immunogenic analyses of these particles.We are currently collaborating with THSTIto test these particles on animals, where various factors such as antibody response, T-cell mediated response and toxicity are tested. These constitute the pre-clinical trials. So far, the vaccine candidate has shown good antigenicity and immunogenicity. We are currently working on drafting a paper to pass these over to a company for eventual commercialisation. This will involve conducting biochemical analyses and testing them on multiple populations.
Other than the field of vaccine study, IIT-D has worked in the field of diagnosis to create Covid testing kits, high efficacy masks, etc."
Of course, developing a vaccine comes with its challenges. Currently, most vaccines require making the virus and then inactivating it, which is a very long process, especially when producing vast quantities. This is why DNA and mRNA vaccines are breakthroughs! They involve generating the coding region of the virus and stabilising it with lipids (in the case of mRNA vaccines) or plasmids (in the case of DNA vaccines). This cuts down the cost of manufacturing and testing. These vaccines are thus very new and exciting, and can potentially revolutionize the field of vaccinology!
Third Wave and the "New Normal"
To return to a pre-Covid like situation, we need herd immunity. This can only be achieved once 60-70% of the population is vaccinated. Currently, only 14-15% of people in India have received two doses, while around 40-45% of people have received one dose. In a country with such a large population, this is no small feat. However, we still have a ways to go before we reach herd immunity. The chances of new strains emerging are also relatively high. “For us to resume our regular activities as soon as possible, we need to continue with what we've been doing- Wearing masks regularly, practising social distancing, and washing and sanitising your hands. I understand that most of us are fatigued by now; however, we cannot slack off. “It's like not driving drunk; [following Covid protocol] has to become second nature for us now,” said Professor Banerjee. Eventually, this pandemic will get to an endemic stage similar to the yearly flu, and will become relatively harmless for most of us. It won’t be possible to eradicate the virus entirely.
When asked about the potential of a third wave in India, Prof. Banerjee had the following thoughts. “At the moment, it is tough to say whether India will face a third wave or not. There are conflicting reports about whether a third wave will occur and if it will be stronger or weaker than the second wave. For example, in the case of influenza, the third wave was actually weaker! People have made mathematical models to try and predict its possibility and whether it will be weaker or not. However, nothing can be said for sure right now. The most we can do is continue to take the necessary precautions and not let down our guard to prevent it from coming.”