Author: Dr Andrew Dickson, Occupational Health Physician
Original document: https://www.cebm.net/wp-content/uploads/2020/03/COVID-CAT-PPE-MASKS-7.pdf
Published by Centre for Evidence-Based Medicine 23 March 2020
Most of the research comparing ‘masks’ (surgical face masks) and ‘respirators’ (FFP3 or similar) relates to influenza or other relatively benign respiratory conditions.
There have been no published trials comparing masks and respirators in the transmission of COVID-19.
Current guidance is therefore based partly on indirect evidence – notably, from past influenza, SARS and MERS outbreaks – as well as expert opinion, custom and practice.
Official UK guidance (February 2020) that both standard and respirator masks provide 80% protection against SARS-CoV-2 was based largely on trials for seasonal flu – so may or may not apply to COVID-19.
For non-aerosol generating procedures (non-AGPs) in clinical care, there is no evidence that respirator masks add value over standard masks when both are used with recommended wider PPE measures.
A recent meta-analysis (total of 9171 participants) found no statistically significant difference in the effectiveness of masks versus respirators in transmission of influenza, avian and swine flu viruses.
A face mask or respirator worn without additional PPE will be less effective.
WHO guidance for all healthcare settings (Author’s note - and thus perhaps transferrable to any close human encounter) recommends:
Triage staff (implicitly, by non-clinical staff without prolonged contact)
Mask + hand hygiene
Suspected or confirmed case of COVID-19 requiring healthcare facility admission and no AGPs
Goggles + hand hygiene, mask,
Suspected or confirmed case of COVID-19 requiring healthcare facility admission and aerosol generating procedures OR collection of specimens for laboratory diagnosis
Goggles + hand hygiene,
The question of whether face masks or other PPE should be worn by individuals maintaining a distance of at least 2 metres is not addressed here
Duties requiring close contact with others (staff for the public): surgical mask recommended. [This would be in line with WHO recommendations for health triage staff. What constitutes close contact is not defined though perhaps within 2 metres].
Staff having close contact with individuals with COVID-19-type symptoms should wear a respirator mask in addition to a gown, goggles and gloves.
Where individuals are likely to be aerosolising from the mouth or nose (e.g. coughing or splitting, perhaps shouting) and have COVID-19-type symptoms wear an FFP3-type respirator in addition to gown, goggles and gloves. The same for individuals taking swabs or other samples for laboratory diagnosis.