RESUMO
BACKGROUND: Reports of transmission of COVID-19 from a vaccinated healthcare worker (HCW) to vaccinated co-workers are sparse. METHODS: Index case (IC): After the second dose of the ChAdOx1 nCoV-19 vaccine, a HCW - our IC was diagnosed of COVID-19 by a rapid antigen test (RAT). A reverse transcription-polymerase chain reaction (RT-PCR) test done on the same day showed a cycle threshold (Ct) value of 10.02 (a very high viral load). Contact tracing and findings: The authors traced IC's contacts and seven contacts were identified. Four of those (P 1-4) were tested positive for COVID-19 on day12 after the contact. P1-2 were vaccinated and had slept near the IC in an enclosed 5.5 × 2.7 × 2.4 m room without air change and without masks, while IC was symptomatic. P3 and P4 came in immediately after IC left that room and slept there without masks. We did not find any other exposures of P1-4 within the 14 days (d) before they tested positive. CONCLUSIONS: P1 and P2 are COVID-19 vaccine breakthrough infections. P3 and P4 contracting infection in the physical absence of IC indicates probable aerosol transmission of COVID-19. The factors that led to this episode, namely, unfamiliarity of breakthrough COVID-19 infections, ignoring the risk of contracting COVID-19 from vaccinated co-workers, hesitancy in seeking medical care soon after the onset of symptoms, poorly ventilated and cramped resting rooms for HCW exists worldwide. This episode reiterates the importance of adhering to basic COVID-19 preventive measures even after vaccination.