A new study in JHI uses a pragmatic time series analysis to provide some data to suggest that stopping a universal mask mandate at St. George’s Hospital in London did not result in an increase in healthcare-associated SARS-CoV-2. The authors were careful to point out that the findings do not show that “masks don’t work”, but rather that in this setting, at this time of the pandemic, removing a universal masking mandate didn’t result in a detectable increase in the rate of healthcare-associated SARS-CoV-2.

I remember early on in the pandemic when people were talking about universal masking (which eventually arrived in the UK in June 2020) feeling that universal masking would have little benefit and we should focus on wearing masks when it mattered (i.e. when caring for patients with respiratory symptoms). In hindsight, it was the right call to go down the route of universal masking early in the pandemic – we had unregulated transmission of SARS-CoV-2 in hospital and community settings, little capacity to tests patients (let alone staff), very little immunity in the community (all of it from natural infection), and severe outcomes from COVID-19 (compared with the more recent clinical picture for most infected individuals). Once we agreed to go down the road of universal masking, I remember many long and difficult conversations to convince people to adopt universal masking – and by that I mean of the mouth and nose (and not of the chin and ear)!

However, times have changed – we have good diagnostics to detect SARS-CoV-2 infection, high levels of immunity in the community (from vaccination and natural infection), and better outcomes from COVID-19. In response to this, we are moving back towards normal healthcare provision, and in line with this, there is no longer a requirement for universal masking in UK hospitals.

In this current study, the authors took the opportunity to evaluate the impact of ceasing universal masking in most wards on healthcare-associated SARS-CoV-2 infection in patients up until September 2023, when universal testing of all admitted patients was stopped. Universal masking was continued in a relatively small number of higher risk units, which were used as a ‘control’, of sorts. The main outcome measure was the rate of healthcare-associated SARS-CoV-2 in patients (defined as a negative admission test and a positive test >7 days after admission) relative to the rate of community-associated SARS-CoV-2 (defined as a positive test in the first 7 days of admission). Using this measure, there was no significant difference in the rate of SARS-CoV-2 infection in either the ‘intervention’ wards (where universal masking ceased) or ‘control’ wards (where universal masking continued). There were also not significant changes in the trend of SARS-CoV-2 infection rate in either group before or after the change in masking.

There are a couple of limitations to consider.

• The study did not include the SARS-CoV-2 infection rates amongst staff, which is a shame, because it would have been really interested to see whether universal masking made a difference here.
• There were big differences in the group of patients included in the ‘intervention’ cohort and ‘control’ cohort, with the control cohort chosen to include patients with a risk of more severe outcome due to COVID-19.
• There are many who will argue that “of course stopping universal masking with a flimsy surgical mask won’t make a scrap of difference – everybody should be wearing FFP3!”.
• The definitions of “healthcare-associated SARS-CoV-2” are problematic. The median incubation period for Omicron SARS-CoV-2 is about 2 days, so many of the patients included in the “community-associated” denominator will, in fact, have been acquired in hospital. The authors did a sensitivity analysis to vary the cut-off point for community vs. hospital attribution, and this didn’t affect the outcome.
• The study period was 10 months – and given seasonal wave patterns in SARS-CoV-2 epi, a longer duration would have been more solid. However, they couldn’t go any further forward (i.e. beyond September 2023) because that’s when universal admission testing ceased.

Am I surprised that stopping universal masking didn’t affect the rate of healthcare-associated SARS-CoV-2? No – in my experience, universal masking was never implemented satisfactorily, and compliance with masks actually covering the mask and nose in a close fitting way was universally poor. Related to this, staff often forgot that during the pandemic, proximity to a newly infected and highly infectious colleague was much higher risk that exposure to a patient who had had COVID-19 for a while and was less infectious.

My view now is that it’s time to move away from universal masking in healthcare settings. And I have had a set of long and difficult conversations with colleagues about moving away from universal masking to match the set that I had about moving into universal masking! Yes, there is an accepted risk of exposure to SARS-CoV-2 and other respiratory viruses from not-yet-diagnosed or asymptomatic infection in patients and staff. But this is a risk that we’ve always accepted. And there are upsides to moving away from universal masking (communication, skin health, environmental, financial). I’d much rather see masks worn really carefully as part of our PPE for dealing with respiratory symptoms.