Emerging science on Covid-19 – Q&A with Dr. Simon Collins
There's been a lot of coverage since July 11th of the story of declining antibody levels. What do you make of it?
A pre-print paper by Seow and colleagues from King's College in London lead to a lot of headlines. Other papers have followed. I'm neither worried nor surprised by declining antibody levels. Antibody levels after recovery are important in so far as they allow our diagnostic blood test to work and tell people "you have had Covid". After that, the issue is not "my antibody levels are declining" (that is not unusual), it's "have I developed an immune memory from the infection I survived and will it mean that if I am re-exposed to Covid in the future, I will mount a robust, immediate immune response which means I have no symptoms or only mild to moderate symptoms at worst?". Immune memory is trickier to measure (I don't think the test is available outside research settings and we don't have access to it). My hope is that the answer on immune memory will turn out to be "yes". We'll know in a few months. Don't worry about declining IgG antibodies (our test will pick up even very low levels of antibodies); hope instead that Covid-19 leads to effective, long-term immune memory.
Will the Abbott blood test you are using reliably detect Covid infections as far back as November 2019?
It should. It's very sensitive. Even minimal antibody levels should produce a 'positive' result. Of the seven tests in its class evaluated to date by Public Health England, it remains the most accurate.
Since late May your team has done Covid antibody blood tests on over 800 patients. What are you seeing in the results?
Most people who have been coming in were unwell in the period late February to early April. Our 'positive' rate is running at 12% but remember, our patient group is a self-selected one, most of whom are suspicious they might have had Covid.
Is 12% a surprise?
No. I suspect the figure for Dublin is about 3% of the population being positive and for the western part of Ireland, about 1%. A big study looking at the positive rate in Spain was published last week in the Lancet and put the country-wide positive rate there at 5% (with Madrid being at 10%).
For people who have positive antibody test results, what are the big scientific questions you would like to see answered?
Infections with viruses from the Coronavirus family lead to immunity. We know the duration varies depending on the virus in question. For Covid-19, my big questions are:
- What is the durability of the immunity (three months, nine months, 18 months)?
- Is that durability equal in a young person with a robust immune system vs. someone aged 80?
- Can those who have had Covid-19 unwittingly re-acquire the virus in their nasal passages in the future, remain well but pass the virus on to others?
What are the arguments in favour of getting an antibody test done at this stage?
It's not my style to go for the hard sell and I worry that if I promote the test, people will say "he would say that, wouldn't he?!". Here's my ten cents on it: if a relative my mine expressed an interest in having the antibody blood test done, I'd say "it's not a waste of time". The test produces either a positive or negative outcome ('detected'/'not detected'). We are seeing no 50:50 ('equivocal') results. If it's positive, with the Abbott test it's basically certain you've had Covid-19 during the past few months. You can then hold on to that result and the value or it will grow or diminish, depending on the emerging science (see 'what are the big scientific questions you would like to see answered', above).
If you test negative, there's a roughly 90% change you have not had Covid, even taking into account inherent test inaccuracies and that fact that a few percent of people don't develop antibodies with infection. Now you know you almost certainly have not had Covid (you might have been convincing yourself that the illness you had in March was Covid!) – and I think you'll be motivated to be vigilant in the coming months, until a vaccine arrives.
Your odds on a Covid-19 vaccine?
Better than 50:50. There'll be more than one. The first won't necessarily be the best. Roll-out in Spring 2021. We might find ourselves being re-vaccinated annually, but so what? We're doing that for flu anyway. The vaccine might be 60% or 70% effective but that would be enough, especially if it transpired that vaccinated people don't go on to end up in ICU if they do catch Covid-19 at a later date.