Welcome to the osmosis daily report on the coronavirus pandemic. I'm Doctor Rishi Desai, the chief medical officer at osmosis
I'm also a pediatric infectious disease physician and I used to work in the division of viral diseases of the CDC doing viral research.
Today, we're gonna talk about trusting antibody testing.
To start us out, there was a report from the WHO about immunity passports and in the very first paragraph of the report
there's this sentence that the news media has really picked up on they write quote:
"There is currently no evidence that people who have recovered from Covid-19 and have antibodies are
protected from a second infection". Now, I think that's a problematic statement for a few reasons.
Maybe they meant that we haven't had human challenge studies where we infect people
purposefully after they've had natural immunity to see if they don't get the infection again.
Or maybe they meant that we haven't followed people that have had natural immunity over time
to see if they have lower rates of reinfection versus someone that's never had the infection before.
And if that's what they mean by no evidence, that's technically true because we haven't given people purposefully the infection
to see if their antibodies are able to ward it off. We also haven't followed people over time
It would take far too long and we haven't had that much time yet to see if having the infection once
really does, in a in a very controlled setting, prevent you from getting reinfection verses someone else.
But let me be clear, that does not mean that we have no evidence.
In fact, we have plenty of evidence that the immune response to an infection is
protective and antibodies are protective against getting the infection again.
Let me explain. Let's start with basic immunology in how all of these vaccines work
when they're targeted towards a virus. What happens in most situations is you get an antibody response and as you can see from this picture
The antibody basically helps your natural killer cells among many other kind of mechanisms,
this is one, to basically destroy virally infected cells. That's a very very basic immunology.
And in fact many vaccines are based on this very fundamental truth. And here's the second data point with macaques.
Where they basically gave them Covid-19 and then tried to reinfect them. And here's what they found.
Their key conclusion is that from this study of monkeys reinfection could not occur if the monkeys had neutralizing antibody.
Again, in monkeys, we've proven now, based on these kinds of tiny tiny trials that having antibody helps.
Here's another study, also in macaques, where instead of giving the macaques an infection
they gave the macaques the vaccine and then they tried to see if the vaccine would prevent
the monkeys from getting sick. And here's their key finding.
They say these antibodies potentially neutralized ten representatives of SARS-COV2 strains,
indicating broad neutralizing ability against the strains circulating worldwide.
So not just one strain, but multiple strains of the virus
So again, we're seeing that antibodies help. This time antibodies that came from the vaccine versus natural infection.
So I hope nobody walks away from reading this
WHO statement thinking that immunity to COVID-19 is not protective
In fact, I believe all the evidence points to the fact that it is protective.
Let's read further in this statement because I think that the key point they're making is a little bit further down.
Here they write lab tests that detect antibodies
in people need further validation to determine accuracy and reliability
Again, the problem is not in the immune system. We know the immune system works to defend you against virus.
The real problem they're citing in the WHO paper is that the lab tests are not as trustworthy
yet because they haven't been validated.
And here's their key worry, they think that if a lab test tells a person that they're immune,
and the person believes the lab test, that they might go out and do things that public health officials don't recommend
and that you might get more cases of disease as a result. So that's that's what they're worried about,
they're worried about the lab test being valid and correct,
not really that your immune system doesn't work against viruses. We know again, that's not the case.
So let's talk briefly about lab testing and whether we know if it works
Let's start with the FDA which has a page about emergency use authorizations.
And if you scroll down what you see is that there are 7 that have been approved for serology
Total of seven from April 24th. You can see three up here and then three more here and
one fine one selects down here in April 1st. So April 1st, April 24th, a total of seven have been approved by the FDA
But we know there are many many other serological tests out there that are just waiting for approval
And so there's a huge logjam here. Now going back to the question from the WHO,
What evidence do we know that these tests work?
Well, let's look at this paper called test performance evaluation of SARS-COV2 serological assays.
It's literally is answering the question that we're posing here.
and what they did was awesome
They basically took 12 test assays out there, not the FDA approved ones
but other ones and they ran them against a set of controls from patients.
Some patients that had known COVID-19 and some that definitely did not have COVID-19.
And they wanted to see how the results would vary between the tests and the data is laid out beautifully.
They have % positive or sensitivity at the top.
They have specificity at the bottom. So let's go one by one.
In terms of percent positive you want that number, of course, to be a hundred percent.
You don't want to miss people that have Covid-19. So looking across all these different studies or tests,
which one performed well?
Well, well first things first, let's look at the fact that they have day since onset, meaning they checked how the assay performed
given more time of disease
So if a person's only had the illness for 5 days versus 10 versus 15
Over all the tests were able to catch a person having immunity when a person had it for longer
So you can see overall the trend is that if you let people have a disease for longer
you're able to detect immunity more effectively. Not always true in every exact case,
you might see some exceptions here on the table, but generally that was the trend. So combining IgG, or
IgM, a positive on either and looking at just 20 days or more of having illness you can see that only one
test actually captured everybody. That was the test from Bio Perfectas.
All the other tests had some misses and the range was between 81 and a hundred percent sensitivity.
Which, actually, to put in perspective is pretty good when you compare that to RT-PCR.
Now on the other side you've got specificity.
In other words, how often are you telling someone that they're immune
and you're certain that they actually are versus you're telling them that they're immune and in fact
they don't have immunity. And this goes to the core issue brought up by the WHO.
And on this scale for specificity
the best test, the only one that got 100% was SureBio. All the other ones had kind of a performance between
84% and 100%. So again, the specificity wasn't actually bad when you compare it to some other tests that are out there
But it wasn't a hundred percent across the board.
Now, this is great data, but the problem is this only captures 12 assays and what we need is something that's done
nationally across all of the different assays that are out there and that study needs to get out there
as quickly as possible so we can figure out what to trust and what not to trust
So bottom line, we need more testing so that we can do more studies like this one
to figure out what to believe and what the cut-offs ought to be for granting immune certificates if that's the road that countries take.
Which likely will be something that many countries will do and some have already done
So thanks for tuning in hit the red subscribe button or the Bell icon to get daily updates
Also, check out osmosis.org/COVID19 for all of our free resources
Remember to do your part to raise the line and flatten the curve. We're all in this together