Quixplained: Stages of Covid-19 vaccine development, and the story so far

There remains uncertainty in India, where the vaccine candidate is undergoing phase-2 and phase-3 trials simultaneously.

Serum Institute of India (SII), which is conducting the trials, had to pause testing after a notice by India’s top drug regulator about the global issue. So far, around 100 participants have been administered the vaccine in India.

The AstraZeneca-Oxford vaccine was among the front-runners of the global candidates.

However, the World Health Organization (WHO) said the pause was not a setback, but a “wake up call” as vaccine development was not always a “fast and straight road”.

Coronavirus vaccine tracker: AstraZeneca’s development process hits a snag after a participant shows signs of severe illness. What does this mean?

The incident demonstrates the importance of following all stages of clinical trial rigorously. What are these stages?

Phase-I is tested on a small group of healthy adult volunteers, maybe one to two dozen, for safety.

Phase-II is usually done on a few hundred healthy adult participants.

Phase-III is tried on thousands of participants.

Participants are usually followed for several months to check on their responses.

The coronavirus vaccine story so far.

The Covid-19 vaccine front-runners.

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