Pfizer says early tests show coronavirus vaccine more than 90% effective

The results are based on 94 trial subjects who were infected by the coronavirus and subsequently developed at least one symptom.

Pfizer said it is now on track to ask health regulators for permission to begin distributing and selling the vaccine – which is two shots weeks apart – by the end of the month, if continued trials demonstrate that the vaccine is safe. 

The Food and Drug Administration requires a company to monitor at least 50% of a study's subjects for side effects for a period of two months before making a safety assessment of the vaccine. Pfizers says it is in on track to collect that data by next week, and could apply for FDA emergency authorization soon after that.

The safety and efficacy check of Pfizer's vaccine was conducted by an independent panel of experts, called a data-safety monitoring committee. They shared their findings with the company on Sunday. 

The company's overall study has required the participation of almost 44,000 individuals in the U.S. and abroad. There have, thus far, been no safety issues. And it is unclear how long the vaccine's protection against the virus will last.

The FDA has said it won't authorize a vaccine unless it is at least 50% effective, and wants to see a higher rate of success in an initial set of trial subjects, to ensure its true efficacy. 

Pfizer's vaccine, which was developed with Germany's BioNTech, was found to be 90% effective seven days following the second shot. 

Pfizer's vaccine is among several that are in late-stage development in the western world, including attempts from Moderna, Johnson & Johnson, and AstraZeneca.