Dr. Farber’s look at coronavirus (COVID-19)

Part 7 (4/26/2020)

Once again, my weekly thoughts on coronavirus.  As always, these are my personal opinions, and I reserve the right to revise them as new information arises.

Probably the major question facing this country is when to re-open it.  Fortunately, polls indicate that most American understand the issue and accept the need for social distancing, masks, and closures, even at personal cost to themselves.  The current recommendation is to wait for two weeks’ worth of steadily dropping new cases in a region.  We don’t have good previous experience with the virus to draw on, but this seems like a very reasonable approach to me. The numbers in Virginia continue to accelerate, so we will be in stay-at-home mode for many more weeks still. 

One of the major items you will be hearing about is the development of antibody testing, so I will devote the rest of the blog to this issue.  For example, ALLCARE walk-in clinics, a multi-state chain, will begin offering the test this week.

Antibodies are part of the body’s immune system.  They help fight off infection, and also provide immunity against being reinfected.   It can take a couple of weeks before they can be detected in the blood or saliva, so a positive test indicates that you have been infected (even if you were asymptomatic), but do not indicate whether you are actively infected, and contagious, now. For that, the current COVID-19 testing (such as we do in the office) looks for actual viral particles.

It is very important that the test not have many false negatives (saying you have antibodies, and are immune, when you are not).  If you are immune, you should be able to go about freely in the community, without worrying that you might catch the disease and/or spread it to others.  You can imagine the possible catastrophe if the test is wrong.  At this time, I have not seen data on the accuracy of the test, so I would not rely on it.

If you are immune, how long does that last?  For most viruses, assuming you are not immunosuppressed (e.g. by chemotherapy), this is life-long.  I had measles as a child, and 50 years later, blood tests showed I was still immune.  Looking at a different virus, rabies, vaccination leads the body to create antibodies which last at least two years (the immunity may be lifelong, but since rabies is almost uniformly fatal, nobody is going to do a study to see just how long it actually does last).  You may think that flu immunity only lasts one year, but it almost certainly lasts well beyond that; the problem is there is a new flu strain each year, which as far as your body is concerned is a new infection, so you need the vaccine yearly.

Having antibodies to coronavirus should be highly protective.  There could be people who get the virus twice, but I expect them to be quite rare.  There have been reports of this happening in some cases, but I feel it is more likely that the diagnosis was incorrect (our current COVID-19 test is not fully accurate) to account for this.  Ongoing studies will answer this question.

How long will natural immunity last?  We do not know that yet. However, I am confident it should last long enough to provide protection until we have a vaccine ready.  Thus, once we have an accurate enough test, it will enable people to know whether they are at risk, and how much precaution they should be taking, until the vaccine is available.

Should you get the test now, before we know how accurate it is?  I will give my answer by quoting from the ALL CLEAR walk-in clinic website itself:  Is it (the test) FDA approved?  Does positive test mean immunity?  NO!

Bottom line, this will be an incredibly valuable test, especially if it can be done in the office or perhaps even at home, but we are not there yet.

As always, good handwashing, wear your masks, and practice social distancing.  And if you are on furlough, take what advantage you can by spending more quality time (nature walks, board games, reading together, etc.) with your children.

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