Why has the Indian government rejected the Pfizer vaccine for COVID even through it has approved the AstraZeneca vaccine?

That is correct that the Indian expert panel on COVID-19 drugs and vaccines has turned down the application made by Pfizer for emergency use authorisation for its vaccine candidate. Incidentally, this is already in use in the US and UK. One of the reasons for the rejection was the absence of any plan on the part of Pfizer to generate safety and immunogenicity data in the local population.

Let us understand these concepts a tad better. Immunogenicity is the ability of a vaccine candidate to generate the desired immune response against a particular pathogen. As a result, Pfizer has decided to withdraw its application on Friday and now it will submit additional data before making a second application for approval on an emergency basis. India has been insistent on having safety and immunogenicity trial in India.

The Indian drug regulator has already decided to not allow emergency use approval for any vaccine candidate unless and until it was backed by adequate and verifiable data from a local bridge trial. A bridge trial should contain safety and immunogenicity data from at least 1600 volunteers to even consider an emergency approval for the vaccine. Pfizer has agreed to reapply with the additional data in place.

The expert committee noted that incidents of palsy, anaphylaxis, and other serious adverse events had been reported during post marketing of the vaccine. Even as the causality was being investigated, Pfizer had not proposed any plan to generate safety and immunogenicity data on the Indian population. Consequently, the committee had not recommended for grant of permission for emergency use in India.

There were also practical considerations. Pfizer had not indicated any plans to manufacture the vaccine in India. That would be a logistical nightmare for India as global stocks were already falling and if they decided focus on proximate geographies, then Indian supplies could be hit. AstraZeneca had already tied up with Serum Institute, Pune for manufacture in its India facilities.

The biggest concern on the vaccine is the storage sophistication that it called for. For example, the Pfizer vaccine requires refrigeration at minus 70 degree Celsius. Such a facility did not exist in India on a commercial scale, making the Astra plan more pragmatic as it only required storage at around -10 degrees centigrade, which was more feasible on a large commercial scale.