Wearing face masks may not have lowered the risk of Covid infection after the first Omicron wave, research has shown, but nevertheless, it still played a valuable risk in slowing down transmission during the first two years of the pandemic, said the experts.
Wearing masks on public transport and airplanes was federally mandated in the US in February 2021 in efforts to reduce the spread of Covid-19, but this was ruled unlawful in April 2022.
Did it actually help stop the spread of the virus?
Paul Hunter, a professor in medicine at the University of East Anglia in the UK, told Newsweek that masks, by themselves, “were never going to be able to eliminate transmission, but they certainly reduced it”.
“Very early in the pandemic we estimated, based on pre-Covid data, that if everyone wore masks we could cut infection by about 20%.”
In late November 2021, the Omicron variant was first identified, becoming the dominant strain in America by late December.
“Before Omicron, never wearing a face mask at work was associated with an increased risk – of 25% to 30% – of testing positive, over those always wearing one,” Hunter said.
“But after the first wave of Omicron, there was no significant difference between people always wearing a mask and those never wearing them, and in children, maybe even a slight reduced risk of testing positive if never wearing a mask.”
In their recent study published in PLOS ONE, Hunter and colleagues from the University of East Anglia analysed official data from the British Office for National Statistics – from November 2021 to May 2022 – to explore how infection risk factors changed before and after the first Omicron wave.
Risk factors included history of foreign travel, household size, employment status, contact with children and wearing a face mask.
“Early in the pandemic there were many studies published looking at risk factors for catching Covid, but far fewer studies after the first year or so,” Hunter said.
“Our research shows that there were changes in some risk factors around the time the Omicron BA.2 variant became dominant.”
In November 2021, always wearing a mask at work, school or in enclosed spaces was associated with a reduced risk of infection in both adults and children. However, after the first Omicron wave, it was not.
So why did the masks suddenly stop working?
“If masks can reduce transmission by about 20% to 30%, then if the virus becomes much more infectious – as was the case with Omicron – 20% to 30% won’t ultimately be enough to slow the infection that much,” Hunter said.
“But the more important issue is that Covid does not generate long-lasting immunity. For highly infectious viruses like Covid with a short duration of immunity, when they have spread through the population once, the number of infections occurring in a population are more affected by the rate at which immunity is lost rather than by changes in behaviour intended to reduce exposure, like wearing masks.
“And people who wore a mask really rigorously throughout the first two years would probably be more susceptible to infection (less immunity) than people who didn’t.”
This doesn’t mean, however, that masks are completely useless, he added.
“There is good evidence that one of the factors behind how sick you get is the size of the dose of virus to which you are exposed.
“So, one suggestion is that if you wear a mask and still catch Covid, you get a lower dose and probably have less severe disease.”
Does that mean we should all still be wearing face masks?
“I think for most of us, the answer is no,” Hunter said. “The majority of people have already had multiple Covid infections by now, but those who are at increased risk of severe disease may still benefit.”
Study details
Changing risk factors for developing SARS-CoV-2 infection from Delta to Omicron
Paul Hunter, Julii Brainard.
Published in PLOS One on 15 May 2024
Abstract
Background
One of the few studies to estimate infection risk with SARS-CoV-2 in the general population was the UK Office of National Statistics Infection Survey. This survey provided data that allowed us to describe and interpret apparent risk factors for testing positive for SARS-CoV-2 in a period when variants and Covid-19 controls experienced large changes.
Method
The ONS published estimates of likelihood of individuals testing positive in two week monitoring periods between 21 November 2021 and 7 May 2022, relating this positivity to social and behavioural factors. We applied meta-regression to these estimates of likelihood of testing positive to determine whether the monitored potential risk factors remained constant during the pandemic.
Results
Some risk factors had consistent relationship with risk of infection (always protective or always linked to higher risk, throughout monitoring period). Other risk factors had variable relationship with risk of infection, with changes seeming to especially correlate with the emergence of Omicron BA.2 dominance. These variable factors were mask-wearing habits, history of foreign travel, household size, working status (retired or not) and contact with children or persons over 70.
Conclusion
Relevance of some risk factors to likelihood of testing positive for SARS-CoV-2 may relate to reinfection risk, variant infectiousness and status of social distancing regulations.
See more from MedicalBrief archives:
Face masks plus distancing increases COVID transmission control — modelling study
Countries with early adoption of face masks showed modest coronavirus infection rates
Despite lack of clinical trial evidence, public should wear face masks – Oxford analysis