The myth of the broken mask? New research finds wearing face masks did not reduce risk of COVID infection after first Omicron wave

Research from the University of East Anglia reveals that wearing face masks did not significantly reduce the risk of Covid-19 infection after the initial Omicron wave. The study analyzed changes in risk factors for infection as the pandemic evolved, noting that factors such as mask use, household size and occupational exposure varied in importance over time . Funded by the National Health and Care Research Institute, the study highlights the need for adaptable risk management strategies and further research to understand these dynamics.

New study says face masks did not significantly reduce risk of Covid-19 infection after initial Omicron wave, highlighting need for adaptable strategies and further research as risk factors evolve .

New findings from the University of East Anglia suggest that wearing face masks did not reduce the risk of Covid infection after the initial rise of the Omicron variant. An analysis of official data indicated that risk factors for infection notably changed when the dominant Covid variant in the UK shifted from Delta to Omicron in December 2021.

These included wearing a mask, foreign travel history, household size, whether people were working or retired, and contact with children or people over 70 .

Lead author Professor Paul Hunter, from Norwich Medical School at the University of East Anglia (UEA), said: “At the start of the pandemic, many studies were published looking at the risk factors for catching Covid, but much less studying after about a year. . Our research shows that there were changes in some risk factors as the Omicron BA.2 variant became dominant.

Co-author Dr Julii Brainard, from UEA’s Norwich Medical School, said: “This is not entirely surprising as laboratory evidence suggests that the Omicron variant was better able to infect cells lining the upper respiratory tract than previous variants and therefore be more effective. transmissible. Infection risk management must be agile, adapt to the development of the epidemic and provide better quality information when it emerges. To prevent infections, we need to have a good idea of ​​which factors might be most or least relevant. If these factors can change, we must be alert to this happening.

Methodology and main data findings

Researchers analyzed available data from the Office for National Statistics (ONS) Covid survey in England, which compared infection rates with an ongoing household survey of the population to estimate the number of people infected. From November 2021 to May 2022, the ONS also asked people about their circumstances and habits to see if these factors could be linked to risk positivity.

Professor Hunter added: “We used this dataset to look for consistency or change in the importance and direction of potential risk factors for a positive test. To do this, we applied a statistical method called meta-regression.

The study found that changes in risk factors included:

• As of November 2021, constantly wearing face masks at work, school or in enclosed spaces was associated with a reduced risk of being infected in both adults and children, but after the first Omicron wave, this was not the case.
• Living in a home with five or more people was a risk at first, but by the end of the study period, people living in larger households (four or more people) had a negligibly higher risk than people living in in isolated households.
• Early foreign travel was not associated with increased risk, but it was later.
• Working in health or social care or in contact with others was often important during the first year of the pandemic, but was not associated with higher infection risk overall or changing during the study period.

• Being an ethnic minority was strongly associated with increased risk during the early months of the UK outbreak, but was associated with lower risk and no significant change in trend during the surveillance period complete study.
• Being retired was associated with reduced risk compared to working people overall, but any protective effect had disappeared by February 27, 2022, which coincided with the start of the second Omicron wave.
• In late February 2022, it became clear that there was a decreased risk for adults living with children aged 16 or younger.
• People under 70 who lived with someone aged 70 or older initially had a lower likelihood of testing positive, but this protective effect diminished around mid-February 2022.

Researchers said the balance of evidence is that wearing face coverings reduces the transmission of respiratory infections in community settings and reduces the transmission of Covid-19. The question, however, is to what extent.

Conclusion and implications for future research

A systematic review of pre-pandemic evidence and an analysis of original survey data during the Covid-19 pandemic both indicated that mask wearing could or did reduce the transmission of SARS-CoV-2 of approximately 19 pc. But these conclusions stem mainly from data before the emergence of the Omicron variants.

This latest research found that before Omicron BA.2, never wearing a mask was associated with an increased risk of around 30% in adults and 10% in children. But during the second Omicron wave (from mid-February 2022), mask wearing had no protective effect in adults and perhaps an increased risk of infection in children.

Professor Paul Hunter commented: “It should not be surprising that risk factors change during a pandemic due to a highly infectious disease with a short duration of immunity like Covid. Epidemic models known as SEIRS (Susceptible, Exposed, Infected, Recovered, Susceptible) predict that such an infection becomes endemic. The risk factors that fueled the outbreak in its early stages are becoming less important, and the rate at which people are losing immunity is becoming more important. in increasing infection rates.

Dr Brainard added: “Many potential risk factors for catching Covid have not changed over this period, and that is also important to know. We offer some possible explanations for why these changes may have occurred, but we would need more focused research to understand with certainty why certain risk factors changed.

Reference: “Changing Risk Factors for Developing SARS-CoV-2 infection from Delta to Omicron” by Paul R. Hunter and Julii Brainard, May 15, 2024, PLOS ONE.
DOI: 10.1371/journal.pone.0299714

The study was funded by the National Institute for Health and Care Research (NIHR) Health Protection Research Unit in Emergency Preparedness and Response at King’s College London, in partnership with the UK Health Safety Agency (UKHSA) and in collaboration with the University of East Anglia.