What a year the last month has been. Every day brings a new batch of scientific studies, government orders, and public health guidance.

The whole world is focused on this coronavirus pandemic, and there are clear priorities. There are big questions that scientists everywhere are racing to answer.

We’ve broken down the big questions and what they mean. They are in some ways the most basic questions — How does it work? How do we fight it? — and answering them will be key to figuring out what the new normal looks like and how we get there.

And while the virus is so new that so much is unknown, the good news, a number of experts said, is that we learn more every day, moving step by step toward answers. Remember, they said: The whole world is on it.

When can you get a vaccine?

Can we develop a vaccine that prevents people from becoming infected? How effective will it be? How long will that immunity last? When will it be available, and how widely?

The virus is so dangerous in part because it’s new — none of our bodies is prepared to fight it. A vaccine helps by training immune systems to prepare for a virus they’ve never encountered before.

Vaccines work by triggering an immune response that creates the proteins needed to fight off the actual virus. So a person who has never been infected, instead of being totally defenseless, now has an immune system that knows how to fight it off.

Why it matters: Widespread vaccination would remove the need for widespread restrictions such as shutdown orders and social distancing.

“A vaccine is a game-changer.” said Yvonne Michael, an epidemiology and biostatistics professor at Drexel University’s Dornsife School of Public Health.

That’s because getting a vaccine not only protects you, it also protects others through “herd immunity.” Not everyone needs to be vaccinated — and not everyone will be able to, including for medical reasons — but if enough people are, it would break the chain of how the virus spreads.

Multiple vaccines are being developed across the globe, but it could take more than a year before one is ready. The vaccines have to be effective and safe, and development and testing takes time.

Why is it you can get barely sick or severely sick?

Why do some people show no symptoms, others very mild ones, and still others die? Why do people experience such different symptoms? What environmental and genetic factors are at play? How much at risk are different groups of people?

This virus can look very different in different people. Some people never show symptoms or only experience mild ones, while others die. For example, older people tend to have more severe symptoms than younger people, and black people in the United States get sicker than white people.

And the symptoms can differ significantly, too.

“It’s actually a little bit scary, the wide clinical presentation of the virus, mainly because you can have people who are asymptomatic walking around, potentially transmitting the virus,” said Darren Boehning, head of biomedical sciences at Cooper Medical School of Rowan University.

What we don’t know yet is why.

Some differences may be because of biology, others about socioeconomic factors and health disparities. Are black Americans genetically more at risk? How much is due to systemic disparities, such as the jobs they work and their access to health care? Do men experience worse outcomes because of biology, or because of sociological factors such as being more likely to smoke?

Why it matters: Knowing the answers means being able to use limited resources more efficiently, such as making sure at-risk groups have more access to testing.

“If you can identify the at-risk groups, you can target them,” Boehning said. “We can direct more aggressive treatment strategies and prevention strategies toward those folks.”

If you get sick, what treatment should you get?

Can we develop drugs that fight the virus itself? If not, can we treat symptoms better than we are? How effective will our medications be, and how widely available?

Right now, there’s no way to treat COVID-19 itself; health-care workers work on the symptoms to allow your body to fight off the infection. That’s why people without severe cases are asked to stay at home if they can, and even to skip getting tested, because being able to confirm a case doesn’t change how the infection is treated. There’s no way right now to deal with the virus itself.

Why it matters: While no medicine is 100% effective for all people, an antiviral that works on the coronavirus would mean being able to prevent serious outcomes, said Annette C. Reboli, the dean of Cooper Medical School.

It could also reduce the spread of the disease by being available, potentially, to people who have the virus but don’t have symptoms.

And medications can sometimes be used prophylactically, said Reboli, an infectious disease physician and epidemiologist. If that’s possible with COVID-19, that would mean high-risk people, such as health-care workers, could take it to prevent getting sick in the first place.

If you get better, what immunity do you then have?

Will people have immunity after recovering from infection? How strong is that immunity? How long does it last? When will be able to accurately test for that immunity?

We don’t yet know whether you will be immune from getting sick again if you’ve gotten the coronavirus and get better. If you are immune, that would help with herd immunity, especially once a vaccine is available. There would be huge changes to how we respond to the pandemic if we can identify people who are immune from becoming infected and from spreading the disease.

“This is the holy grail right now,” said Reynold A. Panettieri Jr., vice chancellor for translational medicine and science at Rutgers University.

But there are many, many questions around immunity. Even if there is immunity, it’s possible that not all recovered people have it. And we don’t know how immune you might be — immunity isn’t as simple as a yes or no, there are degrees — or how long it might last.

Antibody tests will also have to be much more precise than they currently are. Available tests try to look for antibodies to tell whether you were sick, but immunity comes from very specific antibodies. “The problem is, if it’s not a neutralizing antibody, it’s a dud," Panettieri said. “It’s not going to confer immunity.”

Why it matters: Those antibodies could help develop treatments or vaccines. And being able to identify people who are immune could help decide how and when we lift different restrictions.

“If we knew that hundreds or thousands of people are now immune, then we would fashion the deployment of these people back to work strategically, right?” said Panettieri.

Will there be a new strain of the virus?

Will the virus mutate in such a way that it affects people in very different ways? Could it become resistant to the vaccines and treatments we develop? Will we catch the mutation in time to respond?

Viruses mutate, but that doesn’t necessarily mean anything huge changes. The problem is if the coronavirus becomes so different that the answers to the questions above are no longer the same.

“When you see it next spring, it might be different,” said Sreelekha Prakash, a health science professor at Stockton University who specializes in epidemiology.

Why it matters: Antibodies that fight one strain of the virus, for example, might not be able to fight off a variant that develops down the line. That could mean you could be immune to the first strain (through a vaccine or because you got better) but still be susceptible to the second. Similarly, treatment for one strain might not work well for another.

Don’t panic. We don’t know whether that will happen, and even if it does, it may take some time before a significantly different mutation spreads. If the viruses are similar, scientists won’t be starting from scratch with each mutation. Think of the seasonal flu: It shows up each year in a different form, but researchers make a new annual vaccine to match it. And there are treatments that remain the same year after year, used on on whatever strain pops up.

Other unknowns

Will the coronavirus go away in the summer?

Some viruses are less common in the summer, for a lot of reasons including how the virus survives when it’s hotter and more humid, and also how we behave differently in the summer, such as not staying cooped up inside. But others aren’t. So don’t depend on seasonality to solve our problems, experts said, and it doesn’t have a strong impact on the major questions we’re still trying to answer. What seasonality would help with is preparation: A break would give researchers more time to answer these questions. It would also give more time to produce various tests, personal protective equipment, etc.

How can tests be better and more accessible?

Tests for the coronavirus have been far more limited in the United States than officials and public health experts want. Widespread testing — for active infections and for immunity — could allow for much lighter government restrictions. But those tests also need to be accurate, said Igor Burstyn, a public health professor at Drexel.

Can we find out more about how the coronavirus spreads?

The coronavirus is primarily spread through person-to-person contact, mostly through large respiratory droplets. But there are other ways it can be spread, such as by touching something with virus on it and then touching your face. Or through very small particles in the air, which can occur during some hospital procedures (and do not seem to generally happen normally). Better understanding the specifics about how likely you are to get sick could help us know how we can stay safe. Still, because respiratory droplets are known to be the main method of transmission, these questions are less important right now.

How contagious and fatal is the coronavirus?

This was a really important question in the beginning of the outbreak, because it helps determine how far to go to prevent spread. It’s certainly still an important question for understanding the disease, but experts said it’s passed the threshold of contagious and fatal enough that, whatever the specific numbers, we know to take the virus very seriously.