#16,248
For nearly as long as this blog has been running (15 years+), the debate over the effectiveness and use of face coverings (by the general public) during a pandemic has been a topic of heated debate. Up until 18 months ago, the idea - mostly for practical and logistical reasons - had been discouraged by many governments and public health agencies (at least, outside of Asia).
We've known for years that when the next pandemic arrived, there would be a major shortage of PPEs (Personal Protective Equipment) for healthcare personnel (see 2009's Caught With Our Masks Down), and so that limited resource was envisioned reserved for those on the front lines.
Despite years of ominous warnings about the global supply of PPEs, very little was actually done to increase production capacity or our strategic supply I suspect many simply felt a truly bad pandemic would never happen on `their watch', and so they kicked that can down the road for someone else to deal with.
Less expensive, and easier to manufacture, `face covers' (i.e. surgical masks, cloth face masks, etc.) were thought by many to be ineffective in preventing viral transmission. A 2008 NIOSH Science blog called Influenza Pandemic and the Protection of Healthcare Workers with Personal Protective Equipment describes their effectiveness thusly:
This of course assumed a healthcare setting, where HCWs are in close, prolonged contact with probable or confirmed infected patients, and a higher standard of protection is required. There was still some evidence that face coverings could offer useful levels of protection for the general public.Medical masks are not designed or certified to protect the wearer from exposure to airborne hazards. They may offer some limited, as yet largely undefined, protection as a barrier to splashes and large droplets.
However, because of the loose-fitting design of medical masks and their lack of protective engineering, medical masks are not considered personal protective equipment.
- In 2006 the the CDC’s Journal of Emerging Infectious Diseases offered plans for making a simple homemade reusable mask made out of Tee-shirt material (see The Man In The Ironed Mask), which I've highlighted repeatedly over the years.
- Another study, which appeared in PLoS One in 2008 (see What Everyone Will Be Wearing During The Next Pandemic Flu Season), found that homemade masks – while not as effective as N95s – could offer some degree of protection against viral infection.
- In 2010 we looked at a study (see Efficacy of Facemasks Vs. Respirators), that suggests that inexpensive face masks may be more effective than previously thought in protecting against the H1N1 virus.
- And in 2014's MERS: Are Two Surgical Masks Better Than One? - which would become the most viewed blog post on this site (110K+ views) - we looked at some possible strategies for the general public to use to protect themselves during a pandemic.
After 18 months of practical experience, we now have a decent amount of data on the effectiveness of face covers during a pandemic (see here, here, and here).
The general consensus being that while home made or surgical masks aren't as protective as the more expensive and `fit-tested' N95s used in hospitals (see Survival Of The Fit-tested), they do offer some degree of protection to both the wearer, and their contacts.
Adding to this growing knowledge base, today we have a 60-page Expert Panel report to the UK's Health Security Agency (UKHSA) on the role of face coverings in mitigating transmission of the COVID virus, which finds evidence that:
". . . all types of face coverings are, to some extent, effective in reducing transmission of SARS-CoV-2 in both healthcare and public, community settings"
While it matters how you wear such face covers (covering both mouth and nose, and with a tight seal), the evidence for their use continues to grow.
I've reproduced the executive summary below.Research and analysis
The role of face coverings in mitigating the transmission of SARS-CoV-2 virus: statement from the Respiratory Evidence Panel
Published 14 October 2021
Background
Public Health England (PHE) convened an expert Respiratory Evidence Panel in February 2021 to critically assess the evidence behind SARS-CoV-2 transmission to inform their guidance and recommendations.
The panel comprised a group of infectious disease, hygiene, virology, microbiology, respiratory infection, engineering, occupational safety, and infection prevention and control (IPC) experts, including representation on relevant UK advisory panels (Scientific Advisory Group for Emergencies (SAGE) and New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG)).
Nominated individuals participated from UK-wide professional infection societies (British Infection Association, Infection Prevention Society, Healthcare Infection Society, Clinical Virology Network) and the airborne High Consequence Infectious Diseases network, with international participants recommended by the Health and Safety Executive (from the Partnership in European Research in Occupational Safety and Health and the Sheffield Group). Find out more about the list of participants and participants interests.
PHE’s COVID-19 Rapid Evidence Service provided an overview of review-level evidence (searches up to 28 April 2021), refined with input from the panel, and with relevant information extracted and presented.
The key findings below are taken from this synthesis ‘The role of face coverings in mitigating the transmission of COVID-19: an overview of evidence’. Key findings were given a confidence rating (low, medium and high confidence) through combining this overview of evidence with expert knowledge and experience.
The panel met 3 times on 1 March 2021, 21 April 2021 and 12 May 2021.
Key findings and recommendations
The panel assessed review-level evidence (searches up to 28 April 2021) to consider the potential effectiveness of face coverings in mitigating transmission of SARS-CoV-2, including consideration of:
- the role of airborne transmission in relation to SARS-CoV-2
- the transmissibility of new SARS-CoV-2 variants
- the effectiveness of face coverings (including efficacy of different types of face coverings and respirators and factors that may impact on this) [footnote 1]
The panel concluded that:
- airborne transmission beyond 2 metres is possible and that contributory factors to airborne transmission of SARS-CoV-2 include poorly ventilated indoor settings, prolonged exposure and activities that may generate more aerosols (high confidence)
- individual characteristics likely to increase the risk of transmission include high viral load and early symptomatic disease (medium confidence)
- effective ventilation as part of the implementation of the hierarchy of risk controls should be used to reduce airborne exposures beyond 2 metres (high confidence) [footnote 2]
- certain variants of concern (VOCs) are likely to have increased transmissibility, although the magnitude of reported increase varies by geographic region, modelling approach, relative transmissibility of concurrent circulating strains and current control measures in place (medium confidence – Alpha (B.1.1.7) variant, low confidence – Beta (B.1.351) and Gamma (P.1) variants, not considered (given timing of evidence reviewed) – Delta (B.1617.2 variant)
- the biological mechanism of the increase in transmissibility of VOCs is not yet clear, though for Alpha (B.1.1.7) increased transmissibility is likely to be due to either increased viral load (inferred from lower Ct values) or altered dose-response relationship (low confidence)
- the evidence to date suggests that the modes of transmission of VOCs has not changed compared to other variants, so it is expected that the same infection prevention and control measures should be appropriate, including ventilation, hand hygiene, face coverings and, in high risk settings, respiratory personal protective equipment PPE (medium confidence)
- the evidence suggests that all types of face coverings are, to some extent, effective in reducing transmission of SARS-CoV-2 in both healthcare and public, community settings – this is through a combination of source control and protection to the wearer (high confidence)
- laboratory data shows that non-medical masks (such as cloth masks) made of 2 or 3 layers may have similar filtration efficiency to surgical masks (high confidence)
- epidemiological evidence (usually of low or very low certainty) from SARS-CoV-2 and other respiratory viruses suggests that, in healthcare settings, N95 respirators (or equivalent) may be more effective than surgical masks in reducing the risk of infection in the mask wearer [footnote 3] (low confidence)
- evidence, mainly from laboratory studies, suggests that face coverings should be well-fitted and cover the mouth and nose to increase effectiveness (as fit is a limiting factor in the overall mask protective efficiency independently of the filtration efficiency of its fabric) (high confidence)
- there is a need for improved training (in health and care settings) and public health messaging (in community settings) on mask fitting (and quality in the community) (medium confidence)
- there is insufficient evidence to support the use of double-masking in a healthcare setting (not ranked due to insufficient evidence)
- Studies were limited to those on SARS-CoV-2, except relevant reviews and meta-analyses that additionally included other respiratory viruses. ↩
- Based on panel’s expert knowledge and experience (effectiveness of ventilation was not assessed as part of the evidence review). ↩
- However, settings and care interactions are often poorly described in the literature, or include high risk areas within healthcare settings with frequent aerosol generating procedures (AGPs). Evidence in specific care areas is lacking. ↩
While COVID is decreasing right now here in Florida, winter may change the equation, with both COVID and flu. Which is why - in addition to being fully vaccinated against both - I plan to continue wearing a face cover in public for the foreseeable future.
Because the evidence continues to suggest that any mask beats no mask in a viral storm.
