New Delhi: The coronavirus outbreak that was first reported in December 2019 in China, has brought the whole world to a standstill. Over 7 billion people around the world have been waiting for the COVID-19 vaccine now, which has currently more than 100 candidates under development, with a number of these in the human trial phase. 

As per the World Health Organization (WHO), immunization currently prevents 2-3 million deaths every year from diseases like diphtheria, tetanus, pertussis, influenza and measles and there are now vaccines to prevent more than 20 life-threatening diseases

Vaccines work by training and preparing the body’s natural defences, the immune system, to recognize and fight off the viruses and bacteria they target. If the body is exposed to those disease-causing germs later, the body is immediately ready to destroy them, preventing illness.  

According to reports, no unexpected adverse events were identified as part of the coronavirus vaccine research to date. 

Although, some of those COVID-19 vaccinated across the world had short-term minor adverse events such as pain at the injection point and flu-like symptoms including fever, weakness, fatigue, and headache.

This mainly happens because the body’s immune system recognizes the virus and starts fighting it, and then the immunity is prepared against the virus. Subsequently, the second dose of vaccine would be given to people, but its side effects will be less than before. 

Currently, Russia’s has said that its Sputnik V COVID-19 vaccine efficacy is above 95 per cent, 42 days after the first dose, whereas, Moderna’s vaccine is said to be 94.5% effective in preventing coronavirus.

Pfizer has also claimed an efficacy rate of 95 % for its coronavirus vaccine and Oxford-AstraZeneca COVID-19 vaccine is likely to be 90% effective.

This is to be noted that most vaccines have been in use for decades and each vaccine under development first undergoes screenings and evaluations to determine which antigen should be used to invoke an immune response. This preclinical phase is done without testing on humans and an experimental vaccine is first tested in animals to evaluate its safety and potential to prevent disease.

If the vaccine triggers an immune response, it is then tested in human clinical trials in three phases.

During Phase 1, the vaccine is given to a small number of volunteers to assess its safety, confirm it generates an immune response, and determine the right dosage. Generally in this phase vaccines are tested in young, healthy adult volunteers.

In Phase 2, the vaccine is then given to several hundred volunteers to further assess its safety and ability to generate an immune response. Participants in this phase have the same characteristics (such as age, sex) as the people for whom the vaccine is intended. There are usually multiple trials in this phase to evaluate various age groups and different formulations of the vaccine. A group that did not get the vaccine is usually included in phase as a comparator group to determine whether the changes in the vaccinated group are attributed to the vaccine, or have happened by chance. 

In Phase 3, the vaccine is next given to thousands of volunteers – and compared to a similar group of people who didn’t get the vaccine, but received a comparator product – to determine if the vaccine is effective against the disease it is designed to protect against and to study its safety in a much larger group of people. Most of the time phase three trials are conducted across multiple countries and multiple sites within a country to assure the findings of the vaccine performance apply to many different populations. 

During phase two and phase three trials, the volunteers and the scientists conducting the study are shielded from knowing which volunteers had received the vaccine being tested or the comparator product. This is called “blinding” and is necessary to assure that neither the volunteers nor the scientists are influenced in their assessment of safety or effectiveness by knowing who got which product. After the trial is over and all the results are finalized, the volunteers and the trial scientists are informed who received the vaccine and who received the comparator.

When the results of all these clinical trials are available, a series of steps are required, including reviews of efficacy and safety for regulatory and public health policy approvals.