Seeking the key to salvation behind Porton Down’s fences
At the Centre for Applied Microbiology and Research, housed within the high security Defence Science and Technology Laboratory at Porton Down near Salisbury, scientists are poring over 800 blood samples.
They are conducting tests today that will decide the shape and timing of our virus exit strategy. Perhaps, the key to the door that is lockdown.
If the tests work, they will provide the answers to the most important unknowns: How many of us have already had the virus? How common are asymptomatic carriers? And how much immunity, if any, do we acquire after surviving an infection?
The answers will inform not just an exit, through a much more precise modelling of the pandemic’s trajectory, but the best approach to treatments and vaccines.
Little wonder then that this – the “fourth pillar” of the Government’s testing strategy – is being conducted behind high security fences.
“We are so uncertain about the level of infection in the population,” said Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh. “As things stand, we could be out by a factor of 10 or even 100. If work like this gives us even a rough pointer initially, it would be hugely valuable.”
The work at Porton Down is understood to have been under way since January. Experts say the first two months were spent validating hi-tech “assays” for reliably identifying virus antibodies and designing a robust longitudinal blood sampling study. The first 800 blood samples were delivered to the laboratory in late February.
“We are expanding this programme during April so that we have the potential to test around 5,000 samples per week,” said the Department of Health and Social Care. “We will also roll out a national mass population sample over the coming months.”
Attention has been focused on swab tests for the virus and cheap home antibody tests to tell people if they have already been infected. While the swab tests are reasonably precise, the home antibody testing kits are currently woefully inaccurate.
In contrast, the antibody tests or “assays” being run at Porton Down are said to be excellent. “The tools are there. The expertise is there. You can be quite confident PHE at Porton Down has access to sensitive assays that can accurately determine antibody levels in patients’ blood,” said Zania Stamataki, a senior lecturer in viral immunology at the University of Birmingham. He added that it was these Porton Down assays that the commercial antibody tests that the Government has taken options on are being validated against.
The initial aim of the work at Porton Down is to establish how widely the virus has spread. Current models assume the spread to date is fairly modest, at around 3-4 per cent of the population. If the modellers had a more precise grip on this crucial variable, they would be able to predict the course of the epidemic with much greater certainty.
“Data in the coming weeks will enable estimation... with greater precision,” the team at Imperial College London, whose work underpins the UK’S lockdown strategy, admit in a report dated March 30.
Just as a political pollster can take a small but representative sample of the population to establish voting intentions with some accuracy, the scientists at Porton Down hope to pin down a figure for the spread of the virus from the initial 800 blood samples they are currently studying. This will be improved upon as they test more blood samples over time.
The study will also provide data on the vexed question of how many people with Covid-19 experience no symptoms or symptoms so mild they carry on as normal and (perhaps) unwittingly spread the disease to others. This again is vital information for those devising Britain’s exit strategy. Current estimates for non-symptomatic carriers vary hugely.
“Blood antibody tests themselves will not tell you about symptoms but if you have gathered detailed clinical information from those you are taking blood from, it should do,” said Prof Woolhouse.
Karol Sikora, professor of medicine at the University of Buckingham,
‘If work like this gives us even a rough pointer initially [about the level of infection], it would be hugely valuable’
added: “In studies on cruise ships and small countries, where they’ve tested just about everyone, some 50 per cent of people infected have no symptoms. That could mean 20-30 per cent of the population have been infected in the UK, with huge implications for our strategy – especially around herd immunity and NHS capacity. That information really is vital.”
Last, and perhaps most important, the work at Porton Down will – over the course of six months to a year – show whether or not the antibodies produced as a result of contracting Covid-19 give protection against the virus, and how long that protection lasts. Currently, science is completely in the dark about this, the single most important question of all.
“The hypothesis is that the existence of antibodies means you will have some protection but this is not necessarily the case,” said Dr Stamataki. “We do know that antibodies from some existing coronavirus can last for a year or more. But this is a novel virus and it is possible both that its antibodies are not protective or that they don’t last.”
The Porton Down research will establish this by means of a longitudinal study whereby the participants would have their blood checked for antibodies regularly over time to see how long they last.
“One can’t overstate the importance of establishing the strength of any immunity,” said Dr Stamataki. “Even if it lasts for just a year, it would give us the chance to return to normality.”
The work at Porton Down puts into perspective the trouble governments around the world are having with home antibody tests. Even if these tests prove accurate, they are next to useless unless it is known that the antibodies they test for provide protection.
The work at Porton Down should, within months, start to answer that vital question.