Monday, January 25, 2021

Are One In Three People Infected With SARS-CoV-2 Asymptomatic?



Daniel Oran and Eric Topol from the Scripps Institute have done a massive review of multiple studies and have come to the following conclusion:

...At least one of three people infected with SARS-CoV-2, the virus that causes Covid-19, do not develop symptoms. That’s the conclusion of a review we just published in the Annals of Internal Medicine. It summarizes the results of 61 studies with more than 1.8 million people...


Why does this matter to Oran and Topal?

Two reasons...

First, they argue that focusing testing on those folks that are symptomatic likely misses the boat when it comes to population-based viral spread:

...Even though knowledge about asymptomatic infection has greatly evolved, tactics for combating the pandemic have not. It is now obvious that testing only those with symptoms, as was common early in the pandemic, is a mistake because it ignores the invisible legions of infected people who have no symptoms...


Second, they argue that failing to test the asymptomatic could actually make things worse once more arms receive their dose(s) of vaccine:

...The rollout of Covid-19 vaccines brings with it the risk of a new wave of asymptomatic infections. The two vaccines authorized by the Food and Drug Administration {from Pfizer and Moderna} have been proven to prevent illness, but not asymptomatic infection. Even after vaccination, the coronavirus may still temporarily take up residence in the lining of the respiratory tract, making it possible to infect others. Preliminary results from one vaccine trial seem encouraging, with an apparent two-thirds reduction in asymptomatic infection after the first dose. But many other studies are underway.


So what's the solution?

Oran and Topal suggest that we should go big with antigen testing widely applied and done repeatedly like, it turns out, has been successful at some American universities:

...What’s needed is a pivot to a different type of testing. Antigen tests, which look for a bit of coronavirus protein, cost just a few dollars each and can yield results in minutes. Like home pregnancy tests, they require minimal instruction. Antigen tests are ideal for spotting people who are infectious, rather than those who may be long past the infectious phase of Covid-19, or who harbor such low levels of the virus that they are unlikely to infect others.

Inexpensive rapid home tests would help infected people isolate themselves before they could spread the virus. Frequent testing — at least several times per week — is essential, as demonstrated by successful testing efforts at some universities, which have enabled students to return to campus...


Real food for thought, I reckon, as we race to get to vaccine-driven herd immunity before the variants catch us.

(more on the variant stuff tomorrow).



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This story caught my attention because a good friend, colleague and guitar player is getting ready to send his eldest kid to one of the American schools concerned...It was he that first mentioned the succcesses they've had with rigorous, multi-pronged testing...I presume, but stand ready to be corrected, that the same might be said of our local Lotuslandian film industry?
And, to take this further, Topal and Oran conclude that this issue is even worse when you consider the folks who are infectious but 'pre-symptomatic...The piece cited above in STAT News is really worth a read if you are interested but don't want to wade through their scientific paper.


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4 comments:

Booey said...

I think people are under the impression that the vaccine is the end of it and it will set us free. If we can still be carriers after the vaccine and with varients continually being a monkey wrench I think spacing and masks might be with us for a while longer. Bad as it is it's interesting how this virus can manipulate or continually change to become something more proficient, what's the end game?!

Glen Clark said...

It does seem puzzling that testing hasn't been deployed more widely. I suppose that the ultimate test (No pun intended) of any public health strategy is hospitalization rates- and if 'acceptable/stable/declining then testing is a gigantic expense and creates a false sense of security. Indeed, I suspect most governments' (while never admitting)strategy is not to eradicate the virus, just keep it at a tolerable level, not overrun the system and wait for herd immunity (hopefully by way of vaccine).

RossK said...

Booey--

We will really have to see about this once the data come in given that this really wasn't assessed in the Phase III clinical trials for the mRNA vaccines...It is definitely a concern however.

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Glen--

I very much agree that the goal of most govs is to keep things tolerable given that we cannot all be New Zealand, if only for geographic reasons. However, good govs also change course as the data solidify one way or the other. For example, I'm sure that the vaccine roll out plan recently announced by our provincial gov was probably a really difficult decision and they clearly have taken some political heat for it. However, on balance, they clearly could not ignore the fact that age is the biggest factor, by far, for mortality on a population basis.

Another aspect of (rapidly?) solidifying science is that the viral variants do matter... I'm working with a couple of immunologists on non-COVID-related projects who have both have mentioned how much they worry about two things about the variants. The first is how the variants could change, and potentially become more problematic, the more people they pass through. The second (and this is a scary one) is how a weak selective pressure might juice up variant formation and alteration. The latter could occur in conditions of weak immunity after antibody titers start to fall as would likely happen if the interval between first and second mRNA vaccine shots becomes too great. If my colleagues are even half way right about either of these points, increased testing may become a more pressing issue for everyone.


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Ronald said...

Heres a question. What about serology tests to detect antibodies in people who may have already had the virus but don't know it? Back in the summer there was all kinds of media buzz in the US that there could be 10 times as many active cases based on this type of random testing of the population (for example: https://www.nbcnews.com/health/health-news/cdc-says-covid-19-cases-u-s-may-be-10-n1232134)
I haven't heard any more about it since, but based on the Johns Hopkins numbers to date for confirmed cases in the US (26 mill) the US might be close to their herd immunity threshold (aka "rounding the turn"). Or was that CDC reporting in the summer influenced by the fox news induced quakery within that administration?