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World Health Organisation guidelines on social distancing in hospitals and other healthcare facilities are based on poor, outdated evidence, a landmark Australian and US scientific review has found.
Key points:
- The study suggests WHO social distancing and protective equipment guidelines may be inadequate to protect medical staff
- The WHO stands by its recommendation that health workers only use respirators during certain procedures
- The Australian Medical Association says the research should encourage greater caution to protect staff
The global health agency advises medical staff that they do not need any personal protective equipment (PPE) if they maintain at least 1 metre's distance from a COVID-19 patient while performing triage, but staff should offer the patient a face mask.
However, a systematic review of international evidence by public health experts and aerodynamics engineers from the University of New South Wales (UNSW) and the Massachusetts Institute of Technology (MIT) found the 1-2 metre social distancing rule in healthcare settings is out of date and based on "sparse" evidence.
The review of ten studies, published in the Journal of Infectious Diseases this month, also cites guidelines from the European Centre for Disease Prevention and Control, and the US Centres for Disease Control that refer to a 1-metre minimum social distance for medical staff.
"It's a globally accepted rule of infection control that's been around for 80 years and it's never been questioned," co-author and Professor of Global Biosecurity at the UNSW's Kirby Institute, Raina MacIntyre, told ABC News.
"We were interested in what is the actual evidence for this rule.
The study to which Professor MacIntyre was referring was published in 1942.
High-speed exposure technology of the kind available in the 1940s was used during the study to take photographs of secretions from the mouth and nose.
But the UNSW-MIT review found several subsequent studies, all published after 2005, concluded that particles of various sizes could travel at least 1.4 metres from a patient and as far as 8 metres away.
The team turned up 393 papers in an initial search before whittling that number down to ten most-relevant studies.
Of those, eight showed droplets could travel more than 2 metres, according to the review.
"[Although] the studies employed very different methodologies and should be interpreted cautiously, they still confirm that the spatial separation limit of 1m prescribed or droplet precautions, and associated recommendations for staff at ports of entry, are not based on current scientific evidence," the review reads.
The authors found that "the evidence base for current guidelines is sparse, and the available data do not support the 1-2m rule of spatial separation".
PPE guidelines inadequate, author suggests
Professor MacIntyre said a key implication of the research was that World Health Organisation (WHO) guidelines on the use of medical masks and respirators are likely inadequate.
The WHO advises staff to wear a medical face mask, but not a respirator such as an N95 mask, during usual care for patients with COVID-19.
The use of respirators is only recommended during certain procedures understood to generate very light particles from the breath, known as aerosols, such as intubation and resuscitation.
But the review cites research indicating the coronavirus that causes COVID-19 can be dispersed in fine particles in the air, that those particles can travel farther than one metre, and that they can remain in the air for hours at a time.
It also found there is a "continuum" of large droplets to fine particles, and that the two different levels of protection currently advised for health care workers treating COVID-19 patients need re-evaluating.
"Given the high case fatality rate and documented deaths of health workers from COVID-19, the 'precautionary principle' and use of a respirator is warranted.
"The global shortages of PPE should ideally not drive policy. We should instead focus on scaling up PPE manufacturing capacity in all countries."
Study should increase caution, but not a 'slam dunk': AMA
Vice President of the Australian Medical Association (AMA), Dr Chris Zappala, said the UNSW-MIT review underlined the need for caution among medical staff when treating and examining COVID-19 patients.
He said it meant Australian medical institutions could be more confident issuing respirators as something like "default" protection against the disease for staff, and Australia's relatively successful suppression of COVID-19 meant hospitals were in a position to be more liberal with PPE than in other countries.
However, he stressed that clinicians needed discretion over how they protected themselves when treating a wide range of patients in a wide range of environments, and there was no one-size-fits-all approach.
"The 1-metre exclusion may not be enough, and staff definitely need to think about that in the context of what phase of the illness the patient is in," Dr Zappala said.
"If there's any concern, by all means, use an N95 mask.
"[But] we need to be conservative with the personal protective equipment."
He noted that several of the studies cited in the UNSW-MIT review were based on modelling — although some did use human subjects — and did not address environmental factors like humidity and temperature.
"There's only a small amount of evidence to guide us in this regard … [and] this does add to that evidence," he said.
"[But] relaxation of the use of N95s is appropriate."
Dr Zappala stressed that the ongoing use of social isolation, contact tracing and other suppression measures — such as the newly released COVIDSafe app — to keep COVID-19 numbers low were vital to protect healthcare workers long-term.
Guidelines based on best evidence: WHO
In a statement, the WHO said it continues to recommend airborne precautions such as respirators only for use during "aerosol generating procedures".
"WHO continues to recommend airborne precautions for circumstances and settings in which aerosol generating procedures and support treatment are performed, according to risk assessment," it said.
"These recommendations are consistent with other national and international guidelines, including those developed by the European Society of Intensive Care Medicine and Society of Critical Care Medicine and those currently used in Australia, Canada, and United Kingdom.
The WHO's most up-to-date advice on the subject can be found at its website.
Speaking at a press conference last week, WHO Director-General Dr Tedros Adhanom Ghebreyesus said providing evidence-based advice to countries was "one of WHO's core functions".
"This is not something we do alone," he said.
"Every day, we work with thousands of experts all over the world to collect, analyze and synthesize the best science, and turn it into guidance that we give back to countries.
"Through thousands of hours of discussion, we have exchanged first-hand experience and debated the science to generate the advice that we make available to all countries. We then work with countries to turn that guidance into action."
