HEALTH
16/03/2020 8:04 AM AEDT | Updated 16/03/2020 12:12 PM AEDT

Can You Get Coronavirus Again After You've Already Had It?

What is herd immunity? And can you get Covid-19 twice?

The coronavirus is now officially a pandemic, and health officials are warning in no uncertain terms that it is “going to get worse.”

The UK government is reportedly hoping to reduce the impact of Covid-19 by allowing it to pass through the population so we acquire herd immunity, but at a delayed speed.

“Herd immunity” is what happens when a group of people develop enough antibodies to be resistant to an illness. It’s often used in the context of vaccination. For example, if enough people get the flu jab, it’s harder for the illness to spread to those people who cannot have vaccines – like people who are ill or have a weakened immune system.

But there is no vaccination for coronavirus, as of yet. In this case, it seems the idea is that people can gain immunity to diseases after being exposed to them, and once enough people are immune – through exposure – it’ll stop circulating.

HuffPost UK has contacted the Department of Health and Social Care for clarity on how this may work. The UK’s chief scientific adviser, Sir Patrick Vallance, told BBC Radio 4 the advice the government is following is not to “suppress” the disease entirely, but to help create a “herd immunity in the UK” while protecting the most vulnerable from it.

At least 313 people in Australia have tested positive while five people have died after contracting COVID-19.

The virus has infected more than 150,000 people worldwide and killed over 5,600.

When asked if there’s any fear that clamping down too hard on its spread could see it return, Sir Vallance said: “That is exactly the risk you would expect from previous epidemics. If you suppress something very, very hard, when you release those measures it bounces back and it bounces back at the wrong time.” The issue, however, is that consequences could be severe and put the NHS under immense strain, depending on how well the country is able to protect vulnerable people. 

During a press briefing following Thursday’s Cobra meeting, Sir Patrick confirmed that “none of us” have immunity to Covid-19 and added that between 5,000 to 10,000 people in the UK could already be infected.

sorbetto via Getty Images
Here's what we know about COVID-19 and transmission of the disease.

Another big question is whether you can get coronavirus if you’ve already had it. And how long are people contagious for? Here’s what we know so far. 

People may be contagious for a few weeks, and it peaks at a certain point.

According to the Centers for Disease Control and Prevention, “people are thought to be most contagious when they are most symptomatic (the sickest).”

Beyond that, however, the CDC does not have much official guidance about the period of infectiousness for Covid-19 — or about the onset or duration of “viral shedding.” That term refers to the stretch of time during which a person infected with a virus emits it from their body via secretions which, in the case of Covid-19, pretty much means when they are coughing it out. A very small recent study suggested that people may emit high amounts of the virus before they show any symptoms, STAT News reported, but that research has not been peer reviewed. 

The bottom line? “The answer — today — is that people appear to be contagious one to two days prior to getting sick, and for one to two weeks after getting sick,” said Dr Stephen Gluckman, an infectious diseases physician at Penn Medicine and the medical director of Penn Global Medicine. (This timeframe generally goes for any contagious illness, not just Covid-19.)

“As we improve, the amount of virus we’re shedding into the environment drops off,” Gluckman said.

It’s unclear whether reinfection is possible.

Often, when the body is infected by a particular virus, it develops protective antibodies that help prevent repeat infection. That is how, for example, flu vaccination works. 

Dr. Peter Jung, an assistant professor of paediatrics at the University of Texas Medical School at Houston, weighed in on the possibility of reinfection in children: “No one knows for sure, but most children likely develop at least short-term immunity to the specific coronavirus that causes Covid-19,” he said. “But just as the flu can mutate, so could Covid-19, which would make an individual susceptible to reacquiring the infection.”

Other experts feel it is far more likely that once an individual has contracted Covid-19, they will not be able to get it again. 

“Coronaviruses aren’t new, they’ve been around for a long, long time and many species — not just humans — get them. So we know a fair amount about coronaviruses in general,” Gluckman said. “For the most part, the feeling is once you’ve had a specific coronavirus, you are immune. We don’t have enough data to say that with this coronavirus, but it is likely.”

But in the present moment, basically no one has any antibodies that might eventually protect against infection or reinfection. Because Covid-19 is so new, there is “essentially no immunity against this virus in the population,” Dr. Nancy Messonnier, director of the CDC’s National Center for Immunisation and Respiratory Diseases, said in a recent media briefing.  

Prevention continues to be the best defence.

Wash your hands often. Avoid close contact with sick people. Put distance between yourself and other people if Covid-19 is spreading in your community, the CDC has recommended.

And finally, stay informed. Despite the fact that there is much experts do not understand about the virus right now, they are learning more every single day. 

“Panicking doesn’t get you anywhere,” Gluckman said. “But this isn’t simply going away. It’s out of the bag.”

Also on HuffPost