Here’s what you need to know about the Moderna vaccine announcement

Biotechnology company Moderna protocol files for COVID-19 vaccinations are kept at the Research Centers of America in Hollywood, Fla.CHANDAN KHANNA/AFP via Getty Images

The coronavirus vaccine developed by Cambridge-based Moderna Inc. made headlines Monday. Here is a quick rundown on what you need to know:

What’s today’s news?

Moderna said Monday that its experimental COVID-19 vaccine had proven highly effective at preventing coronavirus infections, in the first glimpse of data from its late-stage clinical trial. The news offered another glimmer of light at the end of the coronavirus pandemic tunnel, though experts are still warning there are some deadly and depressing months ahead as cases rise nationwide.

What about the Pfizer vaccine?

This is the second piece of good news regarding vaccines in recent days. Pharmaceutical giant Pfizer reported a week ago that its vaccine candidate was also highly effective. More vaccines may also be on the way: There are a dozen coronavirus vaccine candidates in late-stage trials globally.

How excited should we get?

Cautious optimism is in order. Both Moderna and Pfizer still need to complete their large-scale trials involving thousands of participants. The data released so far are interim results that do not answer key questions, including how long protection against infection might last. Consider that British Prime Minister Boris Johnson is in self-quarantine after being in contact with someone with COVID-19. Back in April, Johnson was hospitalized in intensive care with the virus. “It’s not common, but we have seen sporadic examples of people who have been infected a second time, and we don’t know if that will be the exception or the rule,” said Michael Kinch, director of the Centers for Research Innovation in Biotechnology & Drug Discovery at Washington University in St. Louis.

The two-dose vaccines also will be logistically challenging to distribute to millions of people. And the Pfizer vaccine must be stored at super-cold temperatures.

When will people get the shots?

Both Moderna and Pfizer say they expect to complete more testing and submit their results to federal regulators in the coming weeks for emergency use approval, and both have said they expect to start shipping out millions of doses before the end of the year. But so far, most experts believe there will only be enough to target health care workers, people in elder care facilities, and those with underlying health conditions first.

Anthony Fauci, the nation’s top infectious diseases expert, said Monday on NBC’s “Today” show, “We project that by the end of December, that there will be doses of vaccines available for individuals in the higher-risk category, from both companies, we hope, and this is something that we’re looking forward to.” He said “we want to really get the ball rolling as we get into January, February, and March.”

Fauci said last week he expected vaccines to be more widely available in April.

The Moderna vaccine doesn’t need to be kept at super-cold temperatures. Is that a game-changer?

Moderna now says its vaccine candidate remains stable at standard refrigerator temperatures of 36 degrees to 46 degrees Fahrenheit for 30 days, up from the company’s previous estimate of seven days. And it remains stable for up to six months in a freezer set at minus-4 degrees Fahrenheit. Pfizer’s candidate needs to remain in super-cold storage — roughly minus-103 Fahrenheit — until ready for use, raising concerns about sufficient capacity of super-cold refrigeration units to safely deliver and store millions of doses around the world.

So the Moderna news will make a measurable difference, said Dr. Karen Tashima, director of clinical trials in the Immunology Center at the Miriam Hospital in Rhode Island. “We don’t want to waste vaccine if it’s been sitting in the refrigerator for 8 days. We don’t want to have to throw it out,” she said. “Now we have 30 days. People will feel a lot better about that.”

Will we get to choose which vaccine we receive?

It may depend on refrigeration. If Moderna’s vaccine gets the OK soon, it is expected to be more widely available to areas without super-cold storage capacity, compared with Pfizer’s vaccine. “The big cities that have access to deep freezers clustered around academic research centers, there you would probably use the Pfizer vaccine, whereas in the rural areas, or away from the medical centers, you would presumably want to utilize your warmer-temperature vaccine," Kinch said.

Martin Finucane of the Globe. staff contributed to this report.