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Protecting healthcare workers against SARS-CoV-2 aerosols

Posted by Ann Caluori | Mon, 22/03/2021 - 11:36


Guest blog by Dr Paul Nicholson OBE and Dr Dil Sen


Expert groups have been urging governments to recognise the risk of aerosol transmission of SARS-CoV-2 and to provide healthcare workers with better respiratory protective equipment (RPE). Our editorial recently published in the SOM’s journal Occupational Medicine summarises the evidence which outlines how a) underestimating the risk of aerosol transmission of virus; and b) inadequate supplies of filtering facepiece respirators left many healthcare workers inadequately protected against inhaling aerosols containing the SARS-CoV-2 virus that causes COVID-19.


In spite of the overwhelming evidence supporting aerosol transmission of SARS-CoV-2 consistent policies about on RPE provision are lacking. Partly this is due to countries not stockpiling RPE despite a predicted influenza pandemic. The European Centre for Disease Prevention and Control recommends that healthcare workers use filtering facepiece particulate respirators (FFPR) when in contact with patients suspected or confirmed to have COVID-19. However, country guidelines often cite World Health Organization (WHO) Interim Guidance which only recommended FFPR when performing aerosol-generating procedures on COVID-19 patients; and fluid resistant surgical masks (FRSM) for other healthcare workers in COVID areas - even though WHO revised its guidance in December 2020 to state that FFPRs may be used by all healthcare workers providing care to COVID-19 patients.


Seroprevalence studies show that hospital patients, visitors and healthcare workers are at increased risk of infection; it being estimated that as many as 19% of COVID patients in English hospitals had probable hospital-acquired disease. Healthcare workers who perform aerosol-generating procedures or work in intensive care units (ICUs), though considered to be at greatest risk, are less affected than other healthcare workers. Seropositivity is higher among staff working in housekeeping, emergency departments and general medicine; one study reporting the commonest source of infection to be other healthcare workers. The lower prevalence of infections among healthcare workers considered to be at highest risk is attributed to better air exchange rates and provision of FFPR.


From the outset of the pandemic public health guidance downplayed the role of aerosol transmission. Yet, previous experimental and observational studies have demonstrated aerosol transmission of many respiratory viruses including other coronaviruses. Aerosols are readily dispersed; travel distances exceeding 2 m, aided by heating, ventilation and air conditioning systems; and in the case of SARS-CoV-2 remain infectious in aerosols for several hours.


Urgent action is needed, especially considering that people are more infectious around the time of symptom onset and with the emergence of more easily transmitted variants. Employers should review their risk assessments and hierarchy of controls for managing airborne exposures and must understand that FRSM have never been, nor should they be, regarded as RPE. FRSM only protect against pathogen transmission by splashes or large droplets of body fluids; they are not designed or certified to prevent inhalation of aerosols and viruses. Systematic reviews have concluded that there is no evidence of efficacy for FRSM for healthcare workers - but there is for N95 respirators ‘if worn continually during a shift’. Employers must also assess clinical vulnerability (personal risk factors such as age, ethnicity, gender, health and immune status) for each healthcare worker to determine the protection required.


Public health policies which underestimated the role of aerosol transmission and failure to stockpile adequate supplies of FFPR undoubtedly contributed to healthcare workers being infected at work and infecting colleagues. Healthcare workers have died; others will suffer long-term health effects; and hospitals lost capacity to provide care because of absence attributable to illness or self-isolation.


We conclude that, in general, healthcare workers in high-risk roles and who, as a minimum, use FFPR properly are adequately protected against inhalable SARS-CoV-2; and that healthcare workers in assumed low-risk jobs who are not provided with FFPR, including healthcare workers in non-COVID-19 areas, are not adequately protected against inhalable SARS-CoV-2. We argue for upgrading respiratory protective equipment for all healthcare workers; and for government agencies and employers to learn lessons so that healthcare workers are better protected against this and future pandemics.


You can read Dr Paul Nicholson OBE and Dr Dil Sen's Occupational Medicine editorial here.