"The shorter presentation of symptoms suggests - pending confirmation from viral load studies - that the period of infectiousness might be shorter, which would in turn impact workplace health policies and public health guidance,” the study authors wrote.
While Omicron's lesser severity has been known, the study is unique in its detailed analysis and in that it corrected for any distortions caused by differences in vaccination status by looking at vaccinated volunteers only. The patients - close to 5,000 in each group - were matched and compared 1:1 with a person of the same age, sex, and vaccination dose in the other group.
Among those with only two vaccine doses, symptoms from Delta lasted for 9.6 days and 8.3 days from Omicron, a difference of just 1.3 days.