With a growing number of patients recovering from COVID-19, their blood being tested as a treatment, and the approval of antibody tests to detect exposure, immunity to SARS-CoV-2 is now the center of attention. Is immunity to COVID-19 the key to returning to normalcy?

First, I’m not sure anything will ever be “normal” again. I hope that there will be changes that improve healthcare in the United States. I hope that a pandemic task force is (re)created and staffed with our country’s brightest minds. I hope that we can soon spend money at local restaurants, bars, and stores without putting ourselves and others at risk against an invisible foe that can be spread by healthy people, but that time is not yet today.

Some people have measured this pandemic in only numbers–case counts and dollar signs. Every day, I update the COVID-19 case and death counts for the physician reference DynaMed. I would be better at my job if I saw only numbers, but each day’s Situation Report from the World Health Organization depresses me more than the one before it. Each number I enter into our website is a person–someone’s mom, dad, child, sibling. It is heartbreaking.

We are characters acting out a real-life tragedy, and it may be hard to hear, but we’re not even at intermission yet. Protests demanding reopening the country to get people back to work and spur the economy are shortsighted and dangerous right now. This isn’t meant to minimize the economic impact of the lockdown, it will have ramifications for years to come. But it’s entirely misguided to think that we cannot survive without a robust economy, when in fact we cannot regain a robust economy if we don’t survive.

Reopening the country too soon would be like:
–removing your parachute because your descent slowed when it was opened
–stopping chemotherapy because the cancer stopped spreading
-going off antidepressants because you feel better on them
These are good analogies (all found online, none my own) because they reflect an immediate negative consequence of stopping something due to a positive trend. Just because some areas are seeing a flattening of the curve, doesn’t mean that taking the foot off the brake and stepping on the gas is the next move–and yet that is our country’s plan forward.

A phased reopening is certainly safer than a single flood of everyone out of their houses and into malls, restaurants, and movie theaters. However, the thresholds for each phase unveiled by the Trump administration are not equal in different areas of the country. This doesn’t just apply to different states; local differences in virus spread need to be taken into account. For example, a two-week decline in the number of cases for an entire state doesn’t necessarily equate to a decline in the county or town where you live or work. Similarly, reduction in cases for a city with thousands of infected people is not the same as reduction in cases for an area with only a handful of infections. And the slope of the decline is also an important aspect. A consistent decline of just a few cases might not matter as much as a rapid decent.

I can only hope that our state and local representatives understand this and phased re-opening of our cities and towns reflect the actual safety of each community. I also know that even when shops and restaurants are open, it is within my control to decide to go out or not. I can’t control what other people do, but I can do what’s best for myself and my family. If that means staying at home longer than we’re formally instructed to, particularly for recreational activities, then so-be-it.

I understand that I’m coming from a place of privilege by stating this. I am able to do my job from home, while many of you are not and some of you have lost your jobs altogether. There are so many essential workers risking their own health throughout this lockdown (I appreciate you so much!). Maybe you won’t have a choice to stay home after the lockdown is lifted due to your job or childcare situation. Because of this mixed bag of circumstances, it is that much more important that our representatives err on the conservative side in their decisions for when and how to reopen society. Lives are literally at stake.

So, is immunity the key to reopening society?

In health, the human body is equipped to keep peace and harmony within all its tissues and organs in a physiological state known as homeostasis. The immune system is truly amazing at keeping us healthy by maintaining homeostasis. Its functions range from serving as vacuum cleaners that remove dead cells and debris to playing an essential role in wound healing. The immune system also surveys for infection and cancer and sounds an alarm when an issue is detected. 

During a viral infection, white blood cells called B cells make antibodies that bind up the virus and another cell type called macrophages (the vacuum cleaners) come in and dispose of them. At the same time, T cells seek out and destroy infected cells to stop the virus from replicating itself.

When the virus is eliminated from the body, many of these white blood cells die, but some remain in the body. These cells are called memory cells because they are imprinted with a sort of memory of the infection. If that infection is detected again, memory cells respond quicker and in many cases, they’re able to eliminate the virus before it can make you sick. This is what is known as immunity.

It’s important to keep in mind that immunity is not binary. That is, it’s not that you have it or you don’t. Instead, it’s more of a spectrum depending on how many memory cells survive, what kinds of memory cells they are, and how long they’re functional for. Some immunity, like to varicella zoster virus (chicken pox) lasts for a lifetime. In contrast, immunity to Clostridium tetani, the bacteria that causes tetanus, is nearly nonexistent. Immunity conferred by the annual influenza vaccine can reduce the severity of disease in some people while it can completely prevent disease in others.

The truth is, we’re only safe from COVID-19–as individuals and as a society–when enough of us are immune. You’ve heard about this before, it’s most often called herd immunity, though I prefer to call it community immunity. This refers to a situation where enough people in a community are resistant to infection that the virus runs out of susceptible hosts to infect. Because SARS-CoV-2 is a novel human pathogen, each and every one of us was susceptible at the start of the pandemic and will remain susceptible until we survive infection or get vaccinated. As the proportion of people with immunity rises, there are fewer opportunities for the virus to persist, and it becomes safer to join a crowd again.

In the movie Contagion, Mitch Emhoff, played by Matt Damon, was the first person immune to the fictional MEV-1 virus. He had a known exposure after his wife and son died of the disease. Mitch was isolated in a hospital, but didn’t become sick, and then allowed to reenter society, with one addition–a barcoded wristband or “immunity passport” of sorts. This has been proposed for survivors of COVID-19, but there are a couple potential issues with this strategy.

First, we don’t yet know if durable immunity that fully protects against reinfection in survivors is established. America’s doctor-in-charge, Anthony Fauci said that it’s “likely once you have [COVID-19], you’re protected”. In general, for most acute viral infections that have been studied, this is true. Tests that measure antibodies in the blood have detected ones that can bind up SARS-CoV-2 in recovered patients, but whether these antibodies are enough to prevent another infection is currently unknown. There have been reports of reinfection in South Korea, but it’s unclear if this is true reinfection, reactivation of the virus, or a byproduct of faulty testing.

Second, we still don’t have the testing capacity to find all the asymptomatic and mild cases. Antibody tests have been approved by the FDA, but until mass screening can take place, we don’t know if any of us have been exposed and just didn’t develop disease. Even when blood tests are readily available, we don’t yet know what level or type of antibody confers protection. Until that is understood, the antibody test can only tell us if we’ve been exposed, not whether we’re immune.

If durable immunity is generated to SARS-CoV-2, it can be beneficial in a number of ways. First, those who are immune would be safe to return to the workforce. Second, their blood might be helpful to patients with severe COVID-19. This is still in the very early stages of testing, but 17 of 19 patients that were treated with convalescent plasma (the part of blood containing antibodies from recovered patients) improved in a few small trials. Third, as the number of immune people in each community rises, it becomes safer for non-immune individuals to reenter society because it limits the chance of exposure.

Immunity to COVID-19 will be the key to reopening society, but we’re not prepared to put the key in the lock yet, let alone open the door and step outside. While we will ultimately achieve community immunity of COVID-19 through natural infections AND vaccination, the latter is the safer option. Continuing physical distancing (it doesn’t have to be “social” distancing–call/FaceTime/Zoom your family and friends!) will help spread out infections so that hospitals don’t become overrun. If we can do this together, more of us will be around to re-enter society when it is safe to open the door.

Remember, we’re not stuck at home, we’re safe at home.

Herd Immunity: Why your vaccinations help others