If I Get Coronavirus, Can I Get It Again?

The novel coronavirus that's raced around the world in just a few short months has left devastation and significant loss of life in its wake. This virus, which causes a disease called COVID-19, is so dangerous because humans have no innate immunity to it. Because our immune systems have not faced this specific threat before, they can be easily overrun by the virus' effects.

But what happens if you've had the virus and have recovered from the infection? Will having had the disease mean that you're immune from getting it again? And if so, how long does that immunity last? These are complex questions that require some understanding of basic virology.

[See: Foods That Can Support Your Immunity.]

How Viruses Impact the Immune System

The human immune system is a group of dedicated cells and tissues that fight off infectious agents such as bacteria or viruses. When a virus invades your body, your immune system responds to try to eliminate the virus. This response may include a fever, inflammation and the creation of certain proteins, called antibodies, that help fight the infection. The process doesn't always work, but for many mild viral infections, such as common colds, the immune system is able to contain and mitigate the virus and return your body to health.

Generally speaking, once you have antibodies for a specific pathogen, it's harder to get sick with that same disease again because those antibodies are able to "recognize" the pathogen and deactivate it when it enters the body. Again, it doesn't always work this way, but that's the basic idea of how people can acquire immunity to certain diseases.

Depending on the specific pathogen, these antibodies may stay in your body for months or years, potentially even the rest of your life. This is why it's very unlikely for you to get chickenpox twice -- your body recognizes it if you're exposed again and can usually fight it off.

When your immune system successfully deploys antibodies in response to a virus it has previously responded to, you probably won't get sick with that illness again, so you're considered immune to that specific pathogen. It should be noted, though, that some people who've had chickenpox as children develop a related condition called shingles later in life. Shingles occurs when the chickenpox virus become reactivated in the body, which may occur when you're overly stressed or otherwise unwell -- and the immune system can't function quite how it should.

This is also the underlying principle behind how most vaccines work -- by delivering a dose of either live or inactive viral particles to the body, the immune system ramps up production of the necessary antibodies to fend off a particular illness.

Vaccines are a way of giving your body the immunity it needs to fend off viruses that would cause the flu, measles, polio and other diseases. Those who've been inoculated often never even know they've been exposed or infected with the virus the vaccine protects against.

Not every virus functions the same way, though, and extensive research into whether the SARS-CoV-2 virus that causes COVID-19 generates enough antibodies to impart a durable immune response is unclear. But there's plenty of reason to hope that a vaccine can be developed, and, in fact, clinical trials have already started.

[See: Ways to Boost Your Immune System.]

SARS-CoV-2 and the Immune System

With this current virus, "we don't have all the answers yet," says Dr. Juan Dumois, a pediatric infectious diseases physician at Johns Hopkins All Children's Hospital in St. Petersburg, Florida.

This lack of clear knowledge is an ongoing concern for many, who are trying to find the best way to both treat and prevent COVID-19 infections. Anna Giuliano, founding director of the Center for Immunization and Infection Research in Cancer at the Moffitt Cancer Center in Tampa, says that it's too soon to speculate on whether this particular virus will impart immunity.

For one, it appears that some people who get COVID-19 may not develop antibodies to the virus. Additionally, there are still many other uncertainties related to the body's immune response to this particular pathogen.

"What I can say is that we desperately need research to answer a series of questions," she notes.

Sumit Chanda, director and professor with the Immunity and Pathogenesis Program at Sanford Burnham Prebys Medical Discovery Institute in La Jolla, California, concurs. "The key is going to be (answering) two things," he says.

-- How long do the antibodies provide protection?

-- And two, does the virus mutate to avoid the defense of antibodies?

Other important questions, notes Giuliano, include:

-- What are the characteristics of individuals that develop an antibody and how are they different from people who don't develop an antibody? For example, a preliminary study out of Shanghai indicated that some recovered patients show no evidence of antibodies in the blood. More work needs to be done to understand whether these findings are an anomaly or part of a larger pattern with this disease.

-- Among individuals who do have detectable antibodies to COVID-19, what percent have a recurrent COVID-19 infection and in what time period?

Researchers are racing to answer these questions, and Dumois says "we'll probably learn more about that over the course of the next one to two years and get really definitive numbers and information on that."

For example, is this virus going to behave more like the flu, which changes each year and thus requires a different vaccine formulation each year? Or is it going to be more like tetanus, which is a more stable virus. The tetanus vaccine typically covers you for about 10 years at a stretch.

"At this point, this particular COVID-19 virus seems to be acting more like a stable, nonmutating virus," says Dr. Katherine Dallow, vice president and medical director of clinical programs and strategy for Blue Cross Blue Shield of Massachusetts. If this assumption is confirmed, it means that when a vaccine is developed, you'll likely only need to get it once -- or once every five or 10 years -- to maintain immunity, rather than annually like the flu shot.

But right now, Dallow says "it's far too early" to be making assumptions about how long immunity will last after infection with the SARS-CoV-2 virus. But, "I think that the scientific and epidemiologic community are cautiously optimistic" that this virus may be less like the virus that causes the flu, which mutates frequently and can thus dodge the recognition abilities of the human immune system.

"The overwhelming feeling still at this point is that for the vast majority of people, reinfection risk is minimal," Dallow says. There has been at least one widely reported case of suspected reinfection that impacted a tour guide in Japan. However, Dallow says it's still unclear whether that was a case of reinfection or whether the individual hadn't fully cleared the original infection.

"It could also be the case that for certain individuals -- and I'm not sure we have enough cases to say this for sure -- but that certain individuals may not mount a sustainable viral response, depending on how severely they were infected in the first place," she says. This could mean that because the individual had a very mild case, they might not create enough antibodies to stave off reinfection in the future.

Dallow says that currently, there's very little evidence to suggest this is the case with the SARS-CoV-2 virus, but as with all things related to this coronavirus, more research is needed.

[READ: How to Train and Maintain Your Immune System.]

Antibodies Hold the Key

Chanda notes that people who survived the 2003 SARS outbreak may offer some clues for what we might be able to expect with this virus.

"The two viruses are very, very similar," he says. Researchers are testing the blood of those survivors to see if they still retain antibodies to that virus all these years later. If these survivors still have the antibodies that can block the virus from replicating, that will give us clues as to whether the immune response to the current virus may be long lasting," he explains.

The key to understanding the risk of reinfection and developing treatments for and vaccinations against the SARS-CoV-2 virus all lie in deciphering the antibodies the immune system generates in response to infection with this virus. It's thought that the antibodies generated by people who've previously been infected with COVID-19 could become a viable treatment for the disease, which currently has no treatment, Dumois says.

Researchers in France, China, New York and other locations have begun testing blood plasma (that contains antibodies) from people who've recovered from COVID-19 as a potential treatment for new patients. This method is still experimental, and much more work is needed before this approach can be used widely to treat COVID-19 infection.

Understanding the variations in individual immune response to the virus will also guide future research into treatment and vaccines. "We're trying to understand the widely varying immune response" that people are experiencing with this virus, Dallow says.

Some people are asymptomatic but can still be carriers of the virus and transmit it to others. Others are infected and die quickly. Science doesn't have a complete answer yet for what distinguishes one patient from the other. Until then, Dallow says "it's literally impossible to predict who you may infect and how severely you may infect them."

Therefore, physical distancing (or social distancing) is the best way to stop or slow the spread of the virus to vulnerable people.

The Take Home

For now, it's best to assume that everyone you come into contact with has the virus and could give it to you. Until we know more, it's also best to assume that even if you have recovered from COVID-19 that you could still become reinfected.