What happened

Vaccine stocks rallied on Friday after health officials said the U.S. would expand coronavirus vaccine manufacturing. By the close of trading, shares of Moderna (MRNA -7.82%), BioNTech (BNTX -2.50%), and Novavax (NVAX -7.62%) were up 2%, 5%, and 6%, respectively.

So what

By boosting its production of COVID-19 vaccines, the U.S. will be able to provide more aid to other countries. "We are now working on greatly expanding the capacity to allow us to donate hundreds and hundreds of millions of doses to the low- and middle-income countries," Dr. Anthony Fauci said during an interview on CNBC.

A syringe is in a drug vial that's next to other drug vials.

Image source: Getty Images.

Scientists have debated the merits of making a third dose of Moderna's and BioNTech's COVID-19 vaccines available when many people around the world have yet to receive a single shot. Some health officials believe the U.S. should hold off on booster shots so more vaccines can be made available to other countries.

Fauci, however, doesn't believe those two goals are mutually exclusive. "We are doing both," Fauci said. "We're very sensitive to the needs of the developing world who need vaccine doses, but we believe we can do both."

Now what 

The more people there are who remain unvaccinated, the more opportunities the coronavirus will have to potentially mutate into more contagious and dangerous variants. The delta variant, for one, has led to a surge in infections worldwide. Fauci and other officials know this, and they're desperately trying to make additional vaccine doses available to the billions of people who need them.

Moderna and BioNTech are helping to meet this dire need for safe and effective vaccines. Novavax, which is seeking regulatory clearance for its vaccine candidate, hopes to do so as well. Investors, in turn, are assigning more value to these drugmakers' shares, as the prospect for greater near-term sales increases.