Early vaccine trials on 45 human subjects in Seattle are showing promising results. After 43 days, all 45 volunteers in the study have formed antibodies against the coronavirus, even those receiving the lowest dose of the vaccine. The news has sent the stock market into a huge rally, with some stocks at their highest levels ever. If trials continue to yield positive results, Moderna, the vaccine's maker, says it could be on the market as soon as early 2021.

You may be continuing to follow stay-at-home directives or cautiously starting to reopen. But like every business owner and perhaps nearly everyone on the planet, you know that the effects of Covid-19 on our economy and our society won't completely go away until people are no longer afraid of it. That won't happen until we have an effective vaccine. 

That common dream of an effective vaccine and a return to the world we all used to know came one small step closer to reality on Monday when Moderna announced positive results in its earliest human trials of a coronavirus vaccine. The trials are being conducted at a Kaiser Permanente facility in Seattle in partnership with the National Institutes of Health infectious disease arm led by Anthony Fauci. Researchers gave 45 healthy volunteers either a low, medium, or high dose of the vaccine and a repeat dose 28 days later. Forty-three days after the first dose, subjects in the low dose group had formed antibodies comparable to those found in people who have recovered from Covid-19. And those who got the medium dose had significantly. (Data from the highest dose group is not yet available, Moderna says.)

Although we're still very early in the process, this bit of good news was enough to send the stock markets into a huge rally, with Dow up 900 points and some stocks trading at their highest levels ever, while stocks that benefit from people staying home, such as Amazon and Netflix, are down. Some financial experts caution that this buying spree is an overreaction, and that there is still a very, very long way to go before a vaccine is widely available. But this rally is evidence as good as any of how badly starved people are for good news of any kind about the pandemic.

There's a lot we still don't know about the potential vaccine.

Is it safe? 

Vaccines typically take up to a decade to be approved for the market. The biggest reason is that pharmaceutical companies are supposed to conduct extensive clinical trials to ensure not only that the vaccine works, but also that it won't do more harm than good. Vaccines can have brutal side effects and in rare cases can actually make a disease worse instead of protecting you from it.

Given the worldwide spread of Covid-19 and its death toll of more than 90,000 in the United States alone, any promising vaccine is likely to land on the fast track, as this one has. Health experts warn that there are dangers to releasing a vaccine before we truly know it's safe, but given the risks we're all already facing, that might be a chance worth taking.

At the low and medium dosages, the only ill effect was in one patient who had redness and soreness at the injection site. Three of the patients who received two of the high dose of vaccine suffered fever, muscle aches, and headaches, Moderna reports, although those symptoms went away after a day. In any case, the company says it will only continue trials with the low and medium doses, because their success in producing antibodies appears to render continued testing of the high dose unnecessary. Participants in this first study were between the ages of 18 and 55 and in good health, so we still need to learn how the vaccine might affect people over 60 or with existing medical conditions -- the people most at risk of dying from Covid-19. 

Is it effective?

These results make it clear that the vaccine can activate recipients' immune systems to start producing antibodies to the new coronavirus. One problem, though, is that no one is quite certain yet how much protection antibodies confer to the new coronavirus, or for how long. Generally, people who develop antibodies to a coronavirus -- usually by being infected and then fighting it off -- have at least some immunity for some period of time. But no one quite knows yet how much immunity to Covid-19 antibodies can produce, and there seem to be cases of people who caught the virus, recovered, and then were reinfected, as well as cases of people who tested positive for antibodies but then fell ill. Some health experts believe these are most likely relapses, but we don't yet know for sure.

For obvious reasons, none of the human subjects have been deliberately exposed to the coronavirus to see if they're immune. But researchers have done that with mice and found that the vaccine prevented the virus from replicating within their lungs. So there's good reason to hope, at least for now, that the vaccine provides at least some level of protection.

Moderna's next step is a larger trial with 600 participants to settle on the best dosage. That trial has already been approved and should begin shortly, the company says. If that goes well, Moderna plans to start a wider clinical trial in July, and if that proves successful, apply for a license to distribute the vaccine commercially.

There are many, many unknowns, and many things that can go wrong along the way. But even the possibility that we might have a vaccine less than a year from now is enough to bring some hope to struggling business owners, laid-off employees, and everyone sick of being stuck at home. And hope is something that all of us badly need.