The results add to other early findings from studies of vaccine roll-outs in Israel, Scotland and England, which have also pointed to high effectiveness from the first doses.
"All three of them are really quite good, and people should take the one that's most available to them," Fauci said.
The study and its results have yet to be independently peer-reviewed by other scientists, but could bring the world closer to understanding how vaccines impact transmission.
They are also in talks to test a vaccine modified to protect specifically against the highly transmissible new variant first found in South Africa.
The new target also aims for everyone over 50 or with an underlying health condition to get a vaccine shot by April 15, rather than the previous target of May 1.
Pfizer's vaccine is currently authorized to be taken 21 days apart.
The companies said the 200 million doses are expected to be delivered this year, with an estimated 75 million of them in the second quarter.
One vial of the Pfizer/BioNTech vaccine is now meant for six shots, but it takes special syringes that retain a low volume of solution after an injection.
Health maintenance organization (HMO) Clalit, which covers more than half of all Israelis, said the same group was also 92 per cent less likely to develop severe illness.
Japan’s health ministry said it had approved the vaccine co-developed and supplied by Pfizer Inc.
In theory, lipids should be easy to produce on a large scale, but it gets complicated when the goal is to produce billions of new COVID-19 vaccines for the world.
Moderna and Pfizer will deliver 600 million doses of vaccine by the end of July — more than a month earlier than initially anticipated.
The vaccines being rolled out now require two doses, and people are supposed to get two shots of the same kind, weeks apart.
Vaccine rollouts in the EU have been slow compared to other countries and hampered by problems, including interruptions to their supply chains.
Medical professionals in the United States were first to discover in December that they could get six doses from each vial by using special syringes.
The guidance on Moderna came several weeks after issuing their recommendations on the rival Pfizer vaccine.
On a per capita basis, the U.S. has so far inoculated 5.2 per cent of its population, while Canada stands at 1.09.
A Pfizer spokeswoman said use of the vaccine on pregnant women is "a health regulatory organization's decision."
While it's far from unusual that new drugs come with side effects and potential safety concerns, the deaths of elderly people in Norway have stirred worry.
Pfizer, however, said that such a proposal would first require approval by the U.S. Department of Health and Human Services.