8 ThingsYou NeedTo Know About the New Covid-19 Antibody Tests
Here are 8 FAQs to understand what you need to know about the newly available antibody tests for Covid-19 work, and how they could signal the beginning of the end for quarantine and social distancing. These are really the key to reducing the disruption of our lives and economy so something everyone should know about.
1. What are Antibodies, and what is the difference between Immunoglobulins G and M (‘IgG’ and ‘IgM’)?
Antibodies are proteins made by your body in response to infections. They float around in your bloodstream or body fluids and, when they bump up against the exact germ they were designed to match, they stick to it and ‘flag’ it for destruction by your immune system. Immunoglobulins are a type of antibody.
Without antibodies, your body can’t recognize and fight foreign invaders. Every time you are infected with something new, your body develops new, specific antibodies against it. First it quickly develops an ‘Immunoglobulin M’ (IgM) that exactly matches the germ and is part of the active fight against active infection.
Later, an ‘Immunoglobulin G’ (IgG) is developed that also matches the germ. If that same virus tries to infect you again, that particular matching IgG immediately recognizes the re-infection and your body can fight off the infection much faster, often preventing successful infection completely.
In some cases (as with Chickenpox or Measles), after you have been infected and recovered you continue to have circulating antibodies against those infections forever, making you immune. It works well against viruses that mutate little. Viruses that mutate a lot, like flu, have to be fought from scratch each time because each version is different enough that, although your IgG for your last flu might help, it’s often not enough to provide complete immunity and you have to make ANOTHER IgM and IgG against the new flu. However, for some viruses, you start to produce fewer circulating IgG antibodies over time and you can lose your immunity.
So, the functional difference between IgM and IgG, for the purposes of Covid-19, is that IgM is generally considered an indicator of active or very recent infection, and IgG would be a sign of previous infection and recovery. We’ll revisit why this matters below.
Here’s a summary of how we typically interpret the results of antibody tests:
- At risk/non-immune, or infection could be very recent (within days): IgG negative, IgM negative (or very low in recent infection)
- Infected and actively fighting infection: IgM high, IgG low
- Immune, non-contagious: IgG high, IgM low
2. How does this new antibody test work?
Have you ever used a home pregnancy test? Imagine one of those, but instead of dropping urine into the well on the test, you place a drop of blood — usually from a fingerprick, like when people get their blood sugar checked. After a short time — as little as 20 minutes — the presence or absence of indicator bars means positive or negative for Covid-19 IgG and IgM, and there is one ‘Control’ line that should always appear no matter what (otherwise the test is defective).
Because the test is not 100% accurate, and because someone could be screened so early in their infection that they don’t yet have antibodies, the labeling suggests that people who test negative should be checked again in a few days, and positive results should be confirmed by other methods.
3. How is this test different from previous tests?
Current testing doesn’t look for antibodies — it actually looks for genetic material (RNA) from the virus. If present, the test is positive and you have an active infection. Such tests require nose/throat swabs by trained personnel and are sent to a specialized lab for analysis, in the midst of a global shortage of equipment. They are expensive and cumbersome and take days to get results.
Antibody testing is cheap and fast and easy to use, and can be mass produced and globally distributed easily.
Since testing for the presence of actual viruses only detects active infections, when there are no more viruses, the test will be negative. Until we got antibody tests, there was no way to know if you already had Covid-19, just if you had it right when you were being tested. Antibody tests can reveal not just who is infected (IgM) but also who has been infected and recovered (IgG).
4. How well does this test work?
Covid-19 testing has had mixed success so far (but getting much better fast). Spain had to return tens of thousands of rapid coronavirus tests from a Chinese company after they were found to provide poor results. However, on April 2, the Food & Drug Administration in the US granted first approval to an antibody test for Covid-19 made by Cellex, with an Emergency Use Authorization.
How good is this new test? In the small study so far, the test correctly identified 120 or 128 known positive samples and 239 correct of 250 known negative samples: so about 94% accurate for confirming people with active infection, and about 96% accurate for confirming you DON’T have it. That’s pretty good for a start, certainly good enough that it is promising to let us test a lot more people for both active and past infection.
Negative results do not totally rule out infection; the patient may be so early in the infection that they have not made antibodies yet, or the virus could have slight mutation that makes it missed by the test. There can also be false positives from similar antibodies you have had from previous infections, such as from other coronaviruses.
But overall, it’s pretty darn good and will only get better.
5. What this test will let us learn about Covid-19?
Being able to screen way more people way more easily as well as finding out who already had it and is now recovered will help reveal the true extent of the pandemic (finding those 80% of people who got infected but never knew it) and help scientists answer basic epidemiological questions about Covid-19:
- How many people have actually been infected with the virus (including who may have spread it without knowing it)?
- How deadly is the disease (the average death rate will likely go down once we start adding in all the folks with mild illness or silent infection)?
- Are the tactics we are trying actually working? “If it can’t be measured, it can’t be improved” — and up to now our ability to actually measure how much Covid-19 is out there, and where, is very limited and therefore limiting to our ability to improve our tactics.
6. How will this help us fight further Covid-19 infections?
The majority of people who had Covid-19 don’t even know they had it. Probably a lot of people right now on quarantine lockdown are actually immune and could pretty much go wandering outside without concern of being infected or spreading infection, if they only knew!
One study concluded that 86 per cent of Covid-19 cases were “undocumented” — that is, asymptomatic or had only very mild symptoms so we never knew about them. Although these folks with very mild symptoms were only about 50% as contagious as sicker folks, they caused up to 80% of further infections because there were simply a lot more mildly ill folks than very sick ones, and mildly ill folks were much more likely to be wandering around like normal, spreading virus as they went, compared to someone very sick and in bed at home or in hospital.
World Health Organization assistant director general Bruce Aylward reports that one problem with having symptomatic but untested people stay at home and self-monitor, “is that they don’t know that they have the disease, they haven’t had it confirmed. After a couple of days people get bored, go out for a walk and go shopping and get other people infected. If you know you’re infected you’re more likely to isolate yourself.”
If 80% of infected folks aren’t even feeling sick, they are at home but not isolated: “In China, they found that didn’t work. They had to get them isolated in hospitals or dormitories or stadiums. The main goal was to keep them from getting bored.” People with symptoms isolating at home, untested, got bored and went wandering, so they had to all be sequestered in isolation hospitals and dorms. When they got bored, people who weren’t sure they had it they became less compliant. If they had known, they would likely have been a lot more compliant about isolating, and once they had been shown to have HAD it, they could have just stopped isolating and gone about their normal lives or cared for Covid-19 patients safely.
It will now be much easier and faster and cheaper to screen multiple primary contacts of known Covid-19 patients, giving us the ability to isolate them faster and more effectively and slow the spread of disease. Patients with mild symptoms are more likely to comply with isolation if they know they have Covid-19.
We might also use antibodies harvested from blood donated by Covid-19 patients who have fully recovered as ‘convalescent plasma’ — plasma that contains antibodies to SARS-CoV-2 (the virus that causes COVID-19) might be effective in fighting the infection in very sick patients. Use of convalescent plasma has been studied in outbreaks of other respiratory infections, including the H1N1 pandemic in 2009, the 2003 SARS-CoV-1 epidemic, and the 2012 MERS-CoV epidemic. Although promising, convalescent plasma has not yet been shown to be effective in COVID-19, so the FDA has provided guidelines for physicians seeking approval to give convalescent plasma as part of a clinical trial to demonstrate that it works and inform guidelines on how to use it most effectively. Recovered folks interested in donating can register here.
7. If I had Covid-19, am I really immune? For how long?
In a March study a group of scientists infected rhesus macaques with this new coronavirus, let them recover, then tried to re-infect them. The first infection made them sick, but the second had no effect. “That finding is very encouraging, as it suggests that it is possible to induce protective immunity against the virus,” says Alfredo Garzino-Demo at the University of Maryland School of Medicine.
But that doesn’t necessarily mean long-term immunity. There are other coronaviruses circulating among humans, and, although they induce immunity, this doesn’t last. “Some other viruses in the coronavirus family, such as those that cause common colds, tend to induce immunity that is relatively short-lived at around three months,” says Peter Openshaw at Imperial College London.
Matt Frieman at the University of Maryland School of Medicine in Baltimore, told NPR: “I think there’s a very likely scenario where the virus comes through this year, and everyone gets some level of immunity to it,” he added. “And if it comes back again, we will be protected from it — either completely, or, if you do get re-infected later, a year from now, then you have much less disease.”
Martin Hibbard at the London School of Hygiene and Tropical Medicine echoed the current prevailing opinion in the scientific community: “The evidence is increasingly convincing that infection with SARS-CoV-2 leads to an antibody response that is protective. Most likely this protection is for life…although we need more evidence to be sure of this, people who have recovered are unlikely to be infected with SARS-CoV-2 again.”
A month earlier, a report from Japan revealed that a tour guide had recovered and then tested positive for it three weeks later. However, many suspect this may be because she was not completely recovered and her original infection relapsed.
So, no guarantees are being given yet but most researchers are feeling like lifetime or long-term immunity will occur after infection — plenty long enough to really, really help us get a handle on things.
8. How can this antibody test help end social distancing and quarantine?
“Everyone staying home is just a very blunt measure. That’s what you say when you’ve got really nothing else,” says Emily Gurley, an associate scientist at the Johns Hopkins Bloomberg School of Public Health. “Being able to test folks is really the lynch pin in getting beyond what we’re doing now.”
Since the current evidence points strongly to past infection with Covid-19 providing near-complete immunity, at least for a while, recovered people could essentially go back to work without worrying about catching it, or could safely care for a family member sick with Covid-19. They could donate blood for harvesting antibodies.
Thousands of health workers currently sitting at home in isolation, wondering if they have Covid-19, could be tested and allowed back to work — as well as the legions of other health system support staff — the folks who prepare food in hospitals, do the laundry, collect and incinerate biohazard waste, handle accounting and so on. A workforce of immune folks could be deployed to the front lines of caring for Covid-19 patients with little risk to themselves.
In areas with enough people already immune, enough herd immunity might result that some restrictions can be reduced.
Germany is rolling out a plan to test 100,000 members of the public at a time, issuing documentation-an ‘immunity certificate’ to those who have overcome the virus, as part of a research project being carried out at the Helmholtz Centre for Infection Research in Braunschweig.
Christopher Kirchhoff, a former White House aide who reviewed the U.S. government’s response to the West African Ebola crisis in 2016, is enthusiastic about what widespread confirmation of folks’ immune status means for ending the disruption to our economy and society: “You can imagine asking them to take the key roles in our economy to keep things moving, whether that’s manning a checkout aisle at a supermarket or taking the lead for caring for someone else in their family who comes down with the coronavirus.”
Summary:
The antibody tests may not be perfect, but they are light-years ahead of our previous testing capability and are likely to rapidly revolutionize our approach to Covid-19. Testing is rapidly becoming available; whole organizations have sprung up overnight to offer testing.
Even though making these tests has been a matter of only a couple of months, it’s late in the game for us to be getting them and a massive, massive effort needs to be made to make more of them available and to improve them further.
As we test more people, we should be able to release confirmed recovered (and presumably immune or mostly immune) folks back into circulation and we can start easing the pressure of quarantine — quarantine is the sledgehammer, testing is the scalpel allowing us to start controlling the process instead of reacting to it.
And in the meantime, as the debate about masks rages on, remember one important thing — masks don’t protect your eyes! If the eyes are the windows to the soul, then Covid-19 is a cat burglar waiting to climb right in when you touch your face. In surgery, you wear sterile gloves and don’t touch anything non-sterile before you put your hands into someone, so you don’t transfer germs into them — this is the reverse; you’re trying not to contaminate your hands and then transfer germs into your face mucous membranes.
Since it’s pretty much impossible to ‘just stop’ touching your face, we offer a novel solution that you might already have at home in your camping gear, or can get from Amazon for a few bucks, or even make as a DIY quarantine project yourself — the face veil to prevent touching your face! A lot harder to wipe Covid-19 into your eyes when you physically can’t touch your eyes. Put it down when you leave the house, take it off when you get home and wash your hands.
