Pfizer coronavirus vaccine results leave questions about safety, longevity

The Pfizer trial started less than four months ago, and how long the vaccine will confer protection and how many will benefit are almost complete unknowns for now

Covid-19 vaccine results from Pfizer Inc. and BioNTech SE fueled optimism that the world will soon have a potential way out of the pandemic, yet experts cautioned that the shot still has many hurdles to clear.

Questions about production, distribution and, most importantly, the performance and capability of the shot itself