While hospitals in at least four American states have reinstated mask mandates amid a rise in cases of Covid-19, seasonal flu and other respiratory illness, some experts have criticised updated Covid prevention and control guidelines from the WHO.
Aimed at protecting healthcare works, patients and the community, the new guidance might instead encourage risky behaviour by propagating long-disproven ideas about how viruses spread, some have said.
“I think they put healthcare workers and patients and the community at significant risk,” said Lisa Brosseau, ScD, CIH, an expert on respiratory protection and and infectious diseases and a CIDRAP research consultant.
New York Health Commissioner Dr Ashwin Vasan said last week that mask mandates had resumed at all 11 of the city’s public hospitals, 30 health centres and five long-term care facilities.
“What we don’t want is staffing shortages, right? When we saw the Omicron wave in 2022, the biggest issues were not only people getting sick, but that we had a lot of frontline health workers out with Covid,” he told Reuters.
The most recent weekly data from the Centres for Disease Control and Prevention (CDC) showed more than 29 000 hospitalisations from Covid across the US between 17 and 23 December, up more than 16% from the previous week. The CDC also reported more than 14 700 flu hospitalisations in that same period.
One of the main problems with the WHO update, said Raina Macintyre, MBBS, PhD, professor and head of the biosecurity programme at the Kirby Institute in Sydney, Australia, is that the document doesn't incorporate many of the lessons learned during the pandemic – such as the major role of Covid-19 spread among people with no symptoms.
“The guidelines suggest using symptoms to screen people. This is seen in health guidelines in many countries – emphasis on symptoms (‘wear a mask if you feel unwell’), when we know a substantial proportion of transmission is asymptomatic, which is a major rationale for universal masking in high-transmission settings.”
Similarly, said David Michaels, PhD, MPH, an epidemiologist and professor at George Washington University School of Public Health and a former administrator at the US Occupational Safety and Health Administration (OSHA), the guidelines don’t directly address the modes of transmission.
“I was very disappointed,” he told CIDRAP News, referring to the WHO’s adherence to what he calls “droplet dogma”, or the misguided belief that SARS-CoV-2 spreads mainly through droplets rather than aerosols. “It hasn’t fully recognised the concept that this novel coronavirus is airborne.”
Masks, respirators not equivalent
Nor does the document fully recognise that N95 respirators offer better protection against the virus than medical, or surgical, masks, he added.
Rather, it says the Guideline Development Group (GDG) “considered the evidence for particular respirators versus medical masks and agreed the strength of this evidence was insufficient to recommend one mask over another except in some specific conditions”.
Brosseau said: “There's so much laboratory and workplace research showing how much better a respirator works than a mask. Medical masks and respirators don’t have the same filters: medical masks leak through their filters a lot. They may be similar in capturing large particles, but in small particles, medical masks are very leaky, so it doesn’t really matter how it fits on your face.
“Many of the small particles are still going to exit through the filter and around the facepiece.”
Michaels agreed, saying: “Masks are good as source control for coughing and sneezing, but if a virus is truly airborne, as we think this coronavirus is, while it’s useful, it’s not adequately protective.”
He said he understands the guidelines were the work of a committee that had to reach consensus. “But this is a really important document with global implications. There was a decision made to avoid requiring the best protection for workers, and that’s unfortunate.”
The one-metre rule and other contradictions
Macintyre pointed out that the guidelines recommend physical barriers, like Plexiglass screens, which she said some evidence suggests may be detrimental because they impede airflow.
“The use of the PICO (Patient or problem, Intervention or exposure, Comparison or Control, and Outcomes) framework tends to ignore or trivialise engineering and aerosol science research, when much of the key science around transmission of respiratory pathogens does require research from disciplines other than medicine,” she said.
The WHO recommends people in healthcare settings stay at least a metre apart, when possible. “There’s no discussion of where this one metre comes from,” Michaels said.
“Physical distancing is one of the many precautions worth implementing, because with aerosol transmission, there will be more exposure closer to the source than further away, but why use one metre or two metres or any other number without providing any rationale, any evidence?”
Medical masks
Brosseau highlighted the guidelines’ discussion of how to make medical masks fit better, when they’re not designed to prevent small particles from escaping. “No one has ever cared that a medical mask actually fits, because it’s not designed to fit, and you don’t evaluate a mask for fit,” she said.
“You finally get WHO talking about getting them to fit better and making recommendations on the basis of almost no data,” she added. “So they're willing to talk about laboratory studies for better-fitting masks, but not about laboratory studies for performance of respirators? If they’re worried about the fit of a medical mask, why do they dismiss fit-testing respirators, where it really does matter?”
Longstanding resistance to respirators
The bias against respirators has been evident for years, dating back to 1980s TB outbreaks in the early HIV/Aids epidemic, Brosseau said.
“OSHA even proposed an emergency temporary standard that required the use of respirators for healthcare workers looking after tuberculosis patients, and the CDC and the American Hospital Association and the American Medical Association all lobbied against this. So it was never promulgated as a permanent standard, which is unfortunate because it would have been useful during the pandemic.”
Macintyre concurs. “The ideology that a surgical mask is as good as an N95 respirator has been propagated for a long time, during SARS (severe acute respiratory distress syndrome) in 2003.”
She cited the different results seen in hospitals in two Canadian cities amid SARS (those in Toronto used surgical masks, while those in Vancouver used N95s, resulting in a large epidemic and many deaths only in Toronto).
“And again during the flu pandemic of 2009 and reaching a fevered pitch during the Covid-19 pandemic," she continued. “The sum of evidence clearly shows that a surgical mask is not as protective as an N95.”
Brosseau said those opposed to respirators have noted they can be uncomfortable to wear and aren’t very accessible in low-income countries. Respirators weren’t designed to be worn for hours on end without a break, she added.
Argument for universal respirator use
Macintyre, Michaels, and Brosseau all support universal respirator use in healthcare settings, especially during periods of high respiratory virus community transmission.
“It depends on the overall risk in the region, but certainly universal (respirator use) in periods of increased risk is absolutely vital, because you can’t predict who will be infectious,” Michaels said.
Using respiratory protection only when in close contact with patients diagnosed as having Covid-19 or during aerosol-generating procedures (AGPs) ignores evidence that aerosols can waft through the entire indoor environment for prolonged periods, the experts say.
“The guidelines mistakenly attribute the highest risk to AGPs, but studies show coughing generates more aerosol than an endotracheal intubation,” Macintyre said.
Brosseau said the data support universal respirator use among healthcare workers, at a minimum. “A patient might spend an hour, hour and a half, in a clinic, but a healthcare worker’s exposure is continuous and ongoing, so they have a much greater chance of being exposed than visitors and patients,” she said.
Visitors and patients who can tolerate wearing a respirator should be encouraged to do so, especially during the respiratory virus season, she said: “Even a non-fit-tested respirator is better than a medical mask. If we take what we learned from the pandemic… I think we could probably reduce the burden of respiratory and viral disease overall.”
Michaels said a culture shift was possible and cited the relatively recent use of universal gloving.
“During the HIV/Aids epidemic, OSHA required a blood-borne pathogen standard in healthcare facilities,” he said. “Many people in the dental profession said, ‘How can we work if you make us wear gloves?’ Fortunately, OSHA did not accept their comments, and no one thinks anymore that universal gloving is not an appropriate precaution."
CDC seeks to update guidance to reflect recognition of aerosol viral spread
The CDC has asked the Healthcare Infection Control Practices Advisory Committee (HICPAC) to clarify its guideline on isolation precautions to reflect the “widespread recognition” that respiratory viruses spread primarily through aerosols, according to a CDC blog post this week.
In particular, the CDC is seeking guidance on whether N95 respirators should be mandatory in healthcare settings and, if so, in what circumstances. In November, HICPAC held a public meeting on the CDC’s draft recommendations and, once it receives clarification, it will post the guideline for public comment.
WHO Infection prevention and control in the context of COVID-19: a guideline (Open access)
Reuters article – Mask mandates return at some US hospitals as COVID, flu jump (Open access)
See more from MedicalBrief archives:
Why did it take 2 years for WHO to admit that COVID is airborne?
Most blue surgical masks ineffective against COVID-19 — Canada study
CDC: Most of US no longer needs to be under masking mandates
Latest WHO guidelines advises masks in enclosed areas
New Covid variant – should we be concerned?