Table 2 Distribution of COVID-19 cases in healthcare workers (HW) of Hospital das Clínicas (University of São Paulo) according to the emergence of variants of concern (VOCs) during 2 years of the pandemic (March 10, 2020-March 10, 2022).
From: Reinfection rate in a cohort of healthcare workers over 2 years of the COVID-19 pandemic
Variables | Pre-VOC period | Transition to Gamma* | Gamma period | Transition Gamma to Delta | Delta period | Transition Delta to Omicron | Omicron period |
|---|---|---|---|---|---|---|---|
10 March–30 November, 2020 | 1 December, 2020–14 March, 2021 | 15 March–2 August, 2021 | 3 August–16 September, 2021 | 17 September–2 December, 2021 | 3–31 December, 2021 | 1 January–10 March, 2022 | |
Duration of the period (days) | 265 | 103 | 140 | 44 | 76 | 28 | 68 |
Number of HW tested | 10,195 | 3063 | 4732 | 1679 | 2101 | 894 | 3086 |
Positives for SARS-CoV-2 | 2803 | 602 | 476 | 163 | 103 | 52 | 1666 |
Positivity rate (n of positives/n of HW tested) | 27% | 20% | 10% | 10% | 5% | 6% | 54% |
Mean number of new cases per day | 10.6 | 5.8 | 3.4 | 3.7 | 1.4 | 1.9 | 24.5 |
Number of cases of reinfection | 0 | 7 | 10 | 6 | 4 | 6 | 251 |
Period in which primary infections occurred | – | Pre-VOC = 7 | Pre-VOC = 9 Transition to Gamma = 1 | Pre-VOC = 5 Transition to Gamma = 1 | Pre-VOC = 4 | Pre-VOC = 5 Transition to Gamma = 1 | Pre-VOC = 185 Transition to Gamma = 34 Gamma period = 25 Transition Gamma to Delta = 3 Delta period = 1 |
Reinfection rate (number of reinfections/total cases) | – | 0.2% | 0.3% | 0.2% | 0.1% | 0.1% | 4.2% |
Mean interval between infections in days (range) | – | 258 (193–316) | 344 (126–434) | 359 (187–486) | 533 (506–562) | 505 (319–605) | 507 (122–674) |
Reinfection in vaccinated HW (%) | – | 2 (29) | 10 (100) | 5 (83) | 4 (100) | 6 (100) | 244 (98) |
Reinfection in vaccinated with additional dose (%) | – | NA | NA | NA | 2 (50) | 2 (33) | 177 (71) |
Number of occurrences of a 3rd infection | – | 0 | 0 | 0 | 0 | 0 | 3 |
