Wednesday, May 6, 2020

Testing (for virus and/or antibodies) as a component of ending corona pandemic lockdowns

Yesterday I wrote about how contact tracing could play a big role in relaxing corona pandemic lockdowns.  How about very large scale testing for corona virus? Clearly, it's not one or the other, but one can imagine, and some do, that testing essentially everyone, frequently, could remove the need for indirect methods like tracing contacts.

There are two main things we could test for: virus (infection) and antibodies (indication of past infection).

The main test so far for virus infection, recommended by the CDC, is called a nasopharyngeal swab. It's uncomfortable, but more in a surprising way than a painful one (I am a veteran, and it is surprising how far into your skull your nose goes...). More importantly, it is hazardous for the testers, who could be exposed to the virus while they are probing noses where it lurks.  So they need to be in full hazmat garb, masked and gowned.  And the test I had was not in the hospital or one of the medical office buildings, but on the second floor of the adjacent parking garage (a drive-through test) so that no patients or health care workers or surfaces they might touch would be exposed to infection.

That means the test is hard to administer to many people, or frequently.

Paul Romer argues that the road to ending lockdowns should have every American  tested every two weeks.

It appears that more convenient tests that are also less likely to spread the disease are becoming available.  Here's a story from the WSJ about a saliva test that would allow testees to spit into something and seal it up without exposing the world to possible infection:

Your Spit Could Be the Best Coronavirus Test
As states look for ways to increase their testing capacity, new research suggests that saliva is as effective detecting the virus as swabs

"spitting into a cup appears to be as effective at detecting this virus as sticking a swab into your nose."

Another kind of testing involves blood tests for antibodies to Covid-19. The hope is that individuals with antibodies have acquired substantial immunity to the disease (and hence could return to work). But so far little is known about how much immunity for how long follows recovery from Covid-19, so doubts are emerging about how much can be learned from antibody tests at present.

From the NY Times
Italians Find Promise of Antibodies Remains Elusive, for Now
Talk of licensing people with the right antibodies, always ahead of the science, has faded as experts warn that they are still studying what level offers protection and how long it lasts.
By Jason Horowitz

and in the Lancet:

"Individuals in possession of an immunity passport could be exempt from physical restrictions and could return to work, school, and daily life. However, immunity passports pose considerable scientific, practical, equitable, and legal challenges.

"On April 24, 2020, WHO highlighted current knowledge and technical limitations, advising “[t]here is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection…[a]t this point in the pandemic, there is not enough evidence about the effectiveness of antibody-mediated immunity to guarantee the accuracy of an ‘immunity passport’”.

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