Study begins into how coronavirus spreads and why some people are more affected than others

A group of researchers led by Barts Health in collaboration with colleagues at UCL and Queen Mary University of London have set-up a clinical study of NHS Healthcare Workers to better understand the spread of coronavirus, and why some people are more affected by the virus than others.

This study, which could pave the way for new treatments, is the first to collect samples from healthcare workers on the frontline (doctors, nurses, allied health professionals, administrators and others) who did not have symptoms of the virus. It started before the UK reached the Covid-19 peak.

As part of the study, samples of blood, saliva and nasal swabs from healthcare workers in three London hospitals are being collected in a bid to answer key questions about the virus.

By taking a series of samples from frontline healthcare workers, who were most likely to be exposed early on in the pandemic, the study will help to understand who is most at risk. The team hope that this information will allow them to create individual ‘risk scores’ for developing complications from the virus.

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They also want to know whether people exposed to the virus develop immunity, and if there are any ‘hotspots’ of exposure within a hospital. This research will also help to enhance ways of testing for the virus, and create a library of samples that could be used for drug or vaccine development.

The initial findings, published in The Lancet, show that infection among healthcare workers at present is more likely to reflect general community transmission than exposure within a hospital.

Prof Moon said: “Our research indicates that in the past 2-3 weeks, despite high numbers of patients with Covid-19 in our wards and intensive care units, rates of staff infection have fallen so much that it is unlikely the staff are being infected by patients.

“This low level of infection amongst healthcare staff should reassure patients and visitors that, as the pandemic recedes, infection from healthcare workers without symptoms is unlikely to present major risk.”

With those NHS staff showing symptoms of Covid-19 self-isolating at home, the research found the proportion at work with the disease but no symptoms is very low.

The rate of asymptomatic infection amongst hospital staff fell from 7% to 1% after the UK-wide lockdown was introduced, in line with the general London population.

The researchers are collecting samples from over 400 staff at St Bartholomew’s Hospital displaying no coronavirus symptoms. Blood tests and nasal swabs are taken at weekly intervals.

The research team believe the data reinforces the case for background population surveillance and regular testing of healthcare workers, switching to the testing of all staff, even with no symptoms, if general infection rates rise.

Prof Moon said: “Public fear of hospitals is currently high, with the risk that patients with serious and treatable diseases present too late to prevent adverse outcomes. Our findings show that currently the rate of asymptomatic infection among hospital staff more likely reflects general community transmission than in hospital exposure.”

Prof Noursadeghi, from UCL, who is also involved in the research, said: “Tracking this epidemic will require ongoing monitoring of infection rates in both symptomatic and asymptomatic people in the general population.

"Our data suggest that routine screening of all health care workers without symptoms may not be necessary whilst infection rates in the general population are falling. If they begin to rise again, regular testing of health care workers irrespective of symptoms should be considered to protect these key workers and their patients.”