WHO’s guidance on wearing masks during the covid-19 pandemic does little to clear up public confusion, say Aileen Lai-yam Chan, CC Leung, TH Lam, and KK Cheng

The panic buying of masks seems to have spread faster than coronavirus. Face masks have sold out and been in short supply in many countries, despite media reports that the World Health Organization (WHO) recommends against healthy people wearing them. Amid the confusion, we studied WHO’s interim guidance (dated 29 January 2020) and found that on the question of “to wear or not to wear a mask,” its recommendations seem inconsistent. We took a look at the recommendations point by point and found that it was easy to see why public confusion has arisen:

The advice begins by noting that “Wearing a medical mask is one of the prevention measures to limit spread of certain respiratory diseases, including 2019-nCoV, [since then renamed SARS-CoV-2] in affected areas.” This statement seems to set the scene for the organisation recommending mask wearing as a protective measure for the wearer, as well as for source control of the infection.

However, in the next sentence the guidance notes that “the use of a mask alone (bolded by WHO) is insufficient to provide the adequate level of protection and other equally relevant measures should be adopted. If masks are to be used, this measure must be combined with hand hygiene and other infection prevention and control measures to prevent the human-to-human transmission of 2019-nCov.” The reference here to “protection” suggests that the main purpose of wearing a mask is to protect oneself. It’s worth noting that “being insufficient” does not mean being of “no use.” A healthy diet may not be sufficient to prevent heart attacks, for example, but one normally would not qualify dietary advice like this. “Other equally relevant measures” suggests that wearing a mask works equally well as other measures, such as hand hygiene. And, in fact, there is evidence that masks do provide protection in community settings when worn.

The guidance goes on to say: “Wearing medical masks when not indicated may cause unnecessary cost, procurement burden, and create a false sense of security that can lead to neglecting other essential measures such as hand hygiene practices.” Not having established at this point whether wearing a mask is indicated or not, the guidance places the emphasis on cost, rather than effectiveness in a way that does not seem appropriate. If face masks are effective, of course people would be prepared to pay for them. WHO’s fears of potential procurement burdens have been borne out in countries that have found their healthcare staff are running low on face masks, yet should this not be governments’ responsibility to manage? It’s also debatable if wearing masks engenders a false sense of security. Judging from the panic buying of hand sanitizers and soap, as well as masks, it seems like people are not neglecting to take other precautionary measures even if they’re wearing a mask.

“Furthermore,” as the guidance continues, “using a mask incorrectly may hamper its effectiveness to reduce the risk of transmission.” This statement also suggests that a mask is effective if adopted correctly. Furthermore, if WHO has concerns about an effective preventive measure being used inappropriately, this can be dealt with by education (the excellent WHO video on washing hands is an example of this being done well).

Under a section titled “Community setting,” WHO has further advised that “individuals without respiratory symptoms … should maintain distance of at least 1 meter from any individual with 2019-nCoV respiratory symptoms…” Two studies published around 80 years ago provided the basis for this suggested distance, which has driven hospital infection control, but more recent evidence suggests that droplets can travel further than two meters. This advice, while unambiguous, is also likely to prove difficult in many situations. It is especially challenging in urban settings where people are crowded closely together and it is often unclear as to who is infected or has symptoms. A recommendation that cannot be realistically met may generate a constant sense of insecurity in the wider population, which results in aversive behaviours, including discrimination against people who are seen to be at a higher risk of having the disease. There have been reported incidents of racial discrimination since the onset of the outbreak.

This same section goes on to note that “a medical mask is not required as no evidence is available on its usefulness to protect non-sick persons.” This is not an accurate summary of existing evidence, as there have been trials on the community use of masks by a non-sick person that showed they reduced influenza or flu-like illnesses in the community. These evaluated mixed interventions with hand hygiene and masks and the evidence suggests that when used together they are effective. Commentators have noted that trials that fail to show masks’ effectiveness in protecting wearers may be accounted for by low compliance, which is likely to be a smaller problem in the covid-19 pandemic.

“Individuals with respiratory symptoms” are told in WHO’s guidance that they “should wear a medical mask …” Although there is less evidence to guide us on this specific scenario, it does point towards masks having a benefit for source control. Qualitative research, however, has found that people might avoid this precaution for fear of the stigmatisation and discrimination it might attract. Evidence from patients in China also suggests that asymptomatic patients in the early stages of covid-19 can still infect other people. So how do we ensure that people without obvious symptoms will not infect others? If everyone wears a mask, could it reduce stigmatisation and discrimination, and help to achieve the goal of source control? As asymptomatic “virus shedders” may be fuelling community transmissions, the widespread wearing of masks could be an effective method of source control.

Relatives or caregivers to individuals with suspected covid-19 who have mild respiratory symptoms are told that they “should wear a medical mask when in the same room with the affected individual.” This recommendation would seem to indicate that wearing a medical mask can protect the wearer. It is backed up by some evidence of how to prevent household transmission.

Similarly, WHO advises that healthcare workers “should wear a medical mask when entering a room where patients suspected or confirmed of being infected . . . ” are being cared for. Again, this suggests that wearing a medical mask is highly effective in healthcare workers, a conclusion that is supported by trials.

Finally, WHO concludes that “Cloth masks are not recommended under any circumstance.” This warning is perhaps based on the results of a trial comparing cloth masks with medical masks for healthcare staff in high risk hospital settings in Vietnam, which cautioned against recommending them for healthcare workers. It’s unclear how relevant this finding would be in community settings, especially if the objective is source control. There has been an unfortunate lack of research into cloth masks and no randomised controlled trials seem to have been done on them in community settings. However, homemade cloth masks (although not found to be as effective as surgical masks) have still been shown in laboratory tests to reduce source transmission and block external aerosols.

Evidence points to surgical masks as the superior option, but with their critical shortage and the need to prioritise them for healthcare workers, the public’s use of a cloth mask could help to limit the spread of infection, even if there are only modest benefits in both self-protection and source control. Cloth masks are reusable and there is greater potential for their mass production. It is untested in this context, but so are some of the other social distancing measures being taken (such as the closures of schools) and cloth masks are arguably more practically feasible.

WHO is providing important leadership in the current pandemic. On mask wearing, however, its interim guidance seems to generate confusion and would benefit from urgent revisions that clarify these inconsistencies. During a global health emergency, which WHO have proclaimed covid-19 to be, the public rely on having clear and consistent guidance from those in a position of authority. Unfortunately, WHO’s advice on the use of masks does not meet this need.

Aileen Lai-yam Chan is a retired senior lecturer in arts and communication at the City University of Hong Kong.

Competing interests: None declared.

CC Leung is an honorary consultant of the Hong Kong Tuberculosis, Chest and Heart Diseases Association.

Competing interests: None declared.

TH Lam is chair professor in community medicine and Sir Robert Kotewall professor in public health at the University of Hong Kong.

Competing interests: None declared.

KK Cheng is a professor of public health and primary care at the University of Birmingham. Twitter @KKCheng4

Competing interests: None declared.