After months of work, projections, and predictions, one of the companies leading the race to produce a safe and effective vaccine against the coronavirus has announced the first tangible evidence of real-world efficacy. On Monday, drug manufacturer Pfizer announced that early trial results demonstrate their vaccine is widely effective in preventing infection.

According to The New York Times, Pfizer—which has partnered with German drug company BioNTech—has disclosed information from its ongoing phase III clinical trial that indicates their vaccine was 90 percent effective in healthy volunteers. The Food and Drug Administration, which is responsible for approving any potential vaccine in the U.S., has previously stated that 50 percent effectiveness would be the threshold for potential approval.

The press release provided by Pfizer revealed that 94 people in its 43,558-person trial were infected with coronavirus. The trial will continue until 164 participants have been infected, at which time another review will be conducted.

The early results should not be confused with a trial result, and they have yet to be published in a peer-reviewed medical journal. It’s also not clear how long immunity will last, and as more results come in, the percentage of effectiveness could change. The FDA would also require two months of safety data. Once that milestone is reached later in November, it would allow Pfizer to file for emergency-use authorization.

If the authorization is granted, Pfizer says it would be able to produce 50 million doses of the vaccine, which is given in two shots spaced 21 days apart, by the end of the year. Pfizer executives previously told The New York Times that 15 million to 20 million people could be immunized by then. The limited supply of vaccine would almost certainly be earmarked for at-risk populations like health care workers and the elderly.

The vaccine works by using genetic material known as messenger RNA (mRNA) to “tell” the body to create a protein in the coronavirus. The presence of this protein then triggers an immune system reaction. This approach is also used by Moderna for their vaccine candidate. While the results of their study have yet to be revealed, having a similar mechanism might boost their chances of having an effective vaccine.

Experts have long cautioned that having an effective vaccine is only part of the puzzle. A method of manufacturing and distribution will need to be implemented in order to transport the vaccine—which needs to be kept in extremely cold conditions—and get it to the general population. To that end, Pfizer has been making extensive preparations for delivery of the vaccine, including designing a shipping box that can keep the vaccine at -70°C (-94°F) for up to 10 days.

Reactions from the scientific community thus far have been cautiously optimistic. While final results are still needed, some are saying that these early results could provide a real pathway for a less restrictive 2021.

[h/t The New York Times]