Highly efficient respirators are needed for the Omicron variant of SARS-CoV-2

We read with interest the recent letter of Lowe et al., ¹ who concluded that face masks provide an essentially cheaper and straightforward means for minimizing the infection risk of severe acute respiratory coronavirus 2 (SARS-CoV-2),¹ especially now that the new and highly infective Omicron variant has become prevalent and dominant worldwide. Nevertheless, some additional aspects can be brought in support of this conclusion. First, we have recently shown that the nasopharyngeal viral load in patients infected by the Omicron variant is up to fourfold higher compared with those previously infected by other SARS-CoV-2 lineages,² which would make the adoption of physical interindividual barriers (such as face masks) more compelling than before. The second important aspect concerns the type of mask used for preventing infections. A recent meta-analysis has estimated that the efficacy of medical or surgical masks against the risk of SARS-CoV-2 infection is around 30%, whereas that of N95 or equivalent masks is as high as 70%.³ In keeping with recent data attesting that the volume of exhaled viral particles is magnified in patients infected by the Omicron lineage,⁴ it seems hence advisable not only to reinforce a mask-wearing advice but also to suggest that more efficient respirators (such as N95 or similar) would be preferable to grant major protection against highly infective SARS-CoV-2 lineages such as Omicron.