Another experimental COVID-19 vaccine is proving highly effective in trials, according to its manufacturer, offering the best hope yet that a large portion of the U.S. population will be getting immunized sometime in the coming year.

The company, Moderna, said on Monday that its vaccine is 94.5% effective, based on a study of people who got either the actual vaccine or a placebo as part of a large-scale test that has been underway since the summer.

Of the 95 people in the experiment who developed COVID-19 symptoms, 90 were in the placebo group, with several getting the most severe form of the disease. Of the five in the vaccine group who developed COVID-19 symptoms, none got its severe form.

The results in this trial are truly striking, Dr. Anthony Fauci , director of the National Institute of Allergy and Infectious Diseases, said during a telephone press conference convened by the National Institutes of Health. Id said I would be satisfied with a 70, 75% efficacy, that something like 95% was really aspirational ... Well, our aspirations have been met, and that is really very good news.

Last week, Pfizer announced that its own vaccine was more than 90% effective, based on similar findings.

Both manufacturers have indicated they intend to seek emergency approval from the U.S. Food and Drug Administration, and that if they get approval, they stand ready to start mass production. Moderna says it could produce enough to vaccinate 10 million people in the U.S. by the end of 2020, and Pfizer has said it could produce even more.

Fauci and other experts were quick to issue the same cautionary notes they did last week that this is still based on interim data, and that approval will, and should, depend on more information about safety. The vaccines long-term effectiveness is also an open question. Its not clear how long immunity would last, assuming the preliminary data holds up.

Still, the Moderna news is especially encouraging, because its vaccine works in the same way that Pfizers does. Both use messenger RNA , which the human body uses as code to manufacture proteins.

The vaccines have an artificially engineered version of mRNA that contains the instructions to create part of the COVID-19 virus in particular, the now widely recognizable spiky protein on the virus surface. When people get the vaccine, their cells start to produce the protein and the immune system reacts to it, developing a response that can then prevent the disease when people come into contact with the real virus.

Or, at least, thats always been the hope. Although mRNA vaccines have been in development for many years, nobody has produced and deployed one successfully, as both Pfizer and Moderna now seem to be on the verge of doing.

The Moderna news increases confidence in COVID-19 vaccines for another reason. Although other manufacturers have tried approaches other than mRNA, they are similarly focusing on the spiky protein. If both the Pfizer and Moderna vaccines have indeed succeeded in generating an immune response, thats more reason to think those other vaccines will too.

One of the things that we find is potentially good news for the future... is the consistency across different platforms, Fauci said. All of them use the spike protein as the target ... Although you never want to get ahead of yourself and make predictions before the results of the trials are in, conceptually this looks good.

Nahid Bhadelia , an infectious disease specialist and associate professor at Boston University, told HuffPost that the announcement is good news for sure and bodes well for other vaccines, although she cautioned that the data still needs more review. Also, she said, there are still questions regarding whether these vaccines protect from disease alone or also asymptomatic infection which could allow the vaccinated to continue transmitting and longevity.

The sort of rapid vaccine development associated with the coronavirus is unprecedented in human history. Experts said it was a product of decades of research, including into the development of the mRNA technique, as well as federal efforts through the Trump administrations Warp Speed operation.

Pfizer did not use Warp Speed money to underwrite its research, but Moderna did. Both have secured advance purchases and both expect to profit from sales, though the Trump administration has said the goal is to make sure all Americans get the vaccine for free .

The progress here, I think, does reflect this all-hands-on-deck approach, which has been taken since January by the entire scientific community that being NIH, academic centers and industry all working together in an unprecedented and seamless way, NIH Director Francis Collins said. Operation Warp Speed came along to make sure that all parts of the government were working together, moving swiftly.

The news from Pfizer and Moderna comes just as the U.S. is setting new daily records for COVID-19 cases and hospitalizations, with deaths rising as well. The situation looks more dire than it has at any point since the pandemics early phases, when the virus was brand-new to scientists and providers were still figuring out how to treat it.

Medicine has now developed much better therapeutics, which has helped to reduce fatality rates. But rising caseloads are overwhelming providers in hot spots like the Dakotas and the Rio Grande Valley in Texas and even if the early returns from Pfizer and Moderna hold up, it will be many months before most of the population can get vaccinations, given production timetables.

Distribution will be a huge challenge of its own, especially since the mRNA vaccines require cold storage, although Modernas does not appear to require the same sub-freezing temperatures as Pfizers.

For those reasons, even experts enthusiastic about the vaccine trials say its critical that Americans, and their political leaders, not become complacent.

Its more promising evidence that science will help us end this pandemic, and more reason for everyone to be especially vigilant now to stop this wave of infections, hospitalizations, and deaths, Joshua Sharfstein , a former FDA deputy commissioner who is now a vice dean at the Johns Hopkins Bloomberg School of Public Health, told HuffPost.

We should not let the accomplishment of an effective vaccine have us feel we can let our guard down, Fauci said on the NIH phone call. In fact, it should be an incentive to double down.