If you survive COVID-19, are you immune?
Big implications for herd immunity, 'super workers'
COLE TURNO, a physician assistant from Medford, probably picked up COVID-19 in the emergency room of Massachusetts General Hospital, where he works. Turno’s symptoms have been mild, and after 17 days in quarantine, he is eager to return to work. He wants to help his colleagues, and he believes he has a lower chance than many of them of getting sick, now that he already had the virus.
“There is a semi-joke among colleagues that if you get sick and come back that you’re probably like superhuman,” Turno said. But, he added, “We don’t know. I don’t think anybody knows yet.”
The question of whether someone who had COVID-19 is now immune is one that scientists are frantically studying today, and it has major implications for both the public and the health care workforce. As more and more health care workers fall ill, could recovered workers be able to care for COVID-19 patients with fewer fears of exposure? Could these recovered providers perform procedures that carry more risk of contagion or limit their use of personal protective equipment? On a broader level, if enough people get infected with COVID-19, would that create herd immunity, allowing society to reopen?
Infectious disease specialists say the answer is still unknown. But already tests are being deployed to measure COVID-19 antibodies, which is the first step toward knowing if someone is immune.
Most experts believe that COVID-19 creates short-term immunity.
Studies have shown that, unlike the flu, which mutates into different strains, coronaviruses are more stable. That means once your body develops an antibody to a coronavirus, you are unlikely to get it again.
However, scientists caution that because this virus is so new, no one knows how long the immunity will last. For example, immunity to common coronaviruses – like those that cause colds – generally wanes by the time the next cold season comes around.
“With any viral infection, you almost always develop short-term immunity,” said Todd Ellerin, director of infectious diseases at South Shore Hospital. “What we don’t know is if it comes back next year, will the immunity from the year before help.”
According to Doron, it is known that everyone who develops symptoms of COVID-19 develops antibodies within two weeks.
And testing is beginning to identify those antibodies. The US Food and Drug Administration on April 1 approved the first COVID-19 antibody test, created by the company Cellex.
The FDA is also allowing commercial labs to run these types of tests without FDA review. Framingham-based Boston Heart Diagnostics started offering a blood test on Monday that measures COVID-19 antibodies. The test is not meant to diagnose the virus, but it can be used to determine if someone had COVID-19 in the past and whether the virus is still present.
With an illness like COVID-19, where many people who have the virus don’t show symptoms, the knowledge of who had the virus can be invaluable – especially once more is known about immunity.
Noland said hospitals could use the test to create a business continuity plan. For example, it would help hospital administrators to know they have numerous immune workers in the emergency department but little immunity built up among ambulance drivers.
Doron said Tufts is considering testing all health care workers so that those who had the virus and were asymptomatic can have the peace of mind of knowing they are no longer at risk. “I think we could use it as reassurance, because there’s a lot of fear and anxiety right now even among our bravest,” she said.
Theoretically, Doron said, hospitals could use the information to reconfigure staffing to put immune health care providers on the front lines, or to let them work without personal protective equipment. But she said today, hospitals would not do that because the science around immunity remains unknown.
Rochelle Walensky, chief of infectious diseases at Massachusetts General Hospital, said one question is simply timing. Will the science be more settled around immunity in time to do things like use immune health care providers to take care of the most immunocompromised patients? Walensky said she hopes that by the time more information is known about immunity, which could be several months from now, hospitals will also have been able to solve some of their other problems – like obtaining enough personal protective equipment to protect all employees.
There are other reasons antibody tests are important. Doctors are currently experimenting with treatments for COVID-19 that use plasma from people who developed antibodies. So the test could be used to determine who should donate plasma.
The antibody test could also be a check on how accurate current diagnostic tests are, since there have been reports of patients with COVID-19 symptoms whose diagnostic tests come back negative.
A test could tell individuals – both inside and outside of health care – if it is safe for them to return to work.
On a broader level, there is a point when herd immunity to a disease develops within society. If a certain percentage of the population – scientists are estimating 50 percent to 70 percent – becomes immune, it makes it less likely that there will be another outbreak, and society can reopen. Ideally, Walensky said, herd immunity is developed through a vaccine. With no vaccine available for probably 12 to 18 months, according to expert estimates, herd immunity could develop as more people get the disease.
Today, no one knows what percent of the population is infected, since asymptomatic people generally are not getting tested. Ellerin said widespread antibody testing could be valuable as a surveillance tool, to establish how many people had COVID-19 and whether society is approaching herd immunity.
Having that data would also give a better understanding of the science behind the disease. Ann Sheehy, a biology professor at College of the Holy Cross in Worcester, said today no one knows important information about the virus – like the mortality rate or how many people a single carrier is likely to infect – because the prevalence of the disease is unknown.
Sheehy said antibody testing done on a random sample of individuals – rather than just those who felt ill – would provide the baseline data necessary to understand things like mortality rates or herd immunity. “Knowledge is always power,” Sheehy said.John McDonough, a professor of health policy at Harvard’s T.H. Chan School of Public Health, said researchers in countries like Italy, South Korea, and China that have gotten over the peaks of their outbreaks are now focusing on identifying people who have acquired some degree of immunity – even though there is still no certainty around how long immunity lasts and whether it is similar for everyone.
“This is an example of a global research endeavor, and we’re making important findings every day,” McDonough said. “More to come and a long way to go.”