India has granted permission to administer two vaccines – Covishield and Covaxin. Covishield was developed by Oxford University and AstraZeneca and is manufactured in India by the Serum Institute of India. Covaxin, developed and produced by Bharat Biotech Limited is India’s first indigenous COVID-19 vaccine.

Each person will be injected with the first dose of the vaccines upon registration and be given a booster shot after 28 days. The dosage is the same for both Covishield and Covaxin. However, both the brands cannot be mixed and an individual has to be given the second dose of the same vaccine as the first.

In the research stage, scientists first isolate the virus. They then find out the genetic sequence, following which immune response triggers are checked using various methods. These trials are first conducted on animals and if they develop the immune response, the trials are extended to humans.

Once a vaccine is developed, it is tested in a three-phased manner in humans.

In the first phase, it is given to a smaller group, following which the antibodies that develop in volunteers are analysed. This phase takes about three months to complete.

The vaccine is cleared for the second phase after it proves safe in the first one. In the second stage, several hundred people are administered the trial vaccine. Then, their immune response is checked. Along with that, the safety of the vaccine as well as its adverse reactions are observed in this phase of the trials.

During the third phase, thousands of people are inoculated to assess the impact of the vaccine on a large population group. This may take at least six months to complete.

In the case of COVID 19 vaccines, Phase II and III were fast-tracked in different manners by various companies. Covishield has completed all the three phases of trials while Covaxin has completed only two. The data of the third phase of trials is not available in the public domain.

Usually a vaccine takes years to develop and needs to undergo numerous trials before it is rolled out for public use. But in the case of COVID-19 vaccines, the various processes have been fast-tracked and emergency approvals have been given by the government in view of the urgency of the moment.

Despite the fast-tracking of various phases, starting from the development and pre-clinical stages, both Serum Institute of India and Bharat Biotech have successfully managed to develop a vaccine with the proper immune response to prohibit the viral infection, though not a hundred per cent.

This has become possible due to technological advancements, speeding up of processes as well as availability of the genome sequence of the virus. The genome sequence was shared by Chinese scientists in January 2020.

Because of all these changes in a developmental stage, the vaccines were developed in under a year’s span which otherwise might have taken at least five years.

Vaccine efficacy is calculated as the percentage reduction of the infection in a vaccinated group of persons compared to unvaccinated group of persons.

Let’s assume, we are observing a group of hundred people who have been vaccinated and another hundred who have been administered placebo (or un-vaccinated). Of the two hundred participants, if 95 get infected and five of them belong to the vaccinated group, then the vaccine’s efficacy is tabulated as 95 per cent.

If the vaccine has a lower efficacy, more than one dose is recommended.

Covishield has about 62 per cent proven efficacy.

No. No vaccine can give complete immunity against COVID 19 as of today.

Upon taking the first dose, the immune system of the body is triggered. But the white blood cells activated at that time are very short-lived. Therefore, the body needs a second booster dose of the vaccine to further trigger the immune response for a longer period of time. Many of the vaccines meant for measles, mumps etc. are administered in more than one dose schedule. Taking only one dose might not prove effective in building immunity against the virus.

According to the NITI Aayog chief’s statement, both Covishield and Covaxin are safe to use and have very negligible side effects such as headache, nausea, etc.

According to the health ministry, a person might face minute adverse effects like headache, fatigue, muscle pain, weakness, chills and nausea etc. upon vaccination of Covishield.

For Covaxin, the adverse effects as informed by the ministry include fever, body ache, abdominal pain, giddiness-dizziness, cold, cough and tremors in addition to effects similar to Covishield.

Also, lactating mothers, pregnant women and persons under 18 years of age are not allowed to be vaccinated.