Abstract
Background: Despite the extraordinary speed of mass vaccination efforts, an outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) delta variant in a vaccinee with coronavirus disease 2019 (COVID-19) mRNA vaccine was identified in an adult day service center (ADSC) of Jeju, South Korea. The primary objective of this study was to investigate the epidemiologic features in infection-vulnerable facilities with a high vaccination rate of BNT162b2 mRNA COVID-19 vaccine. The second was to estimate the secondary transmission prevention effect of the vaccine in the household members by vaccination status.
Methods: We included all ADSC participants, staff and their household members. All COVID-19 infected cases were confirmed by reverse transcriptase polymerase chain reaction. We calculated attack rate in ADSC and the secondary attack rate (SAR) in household members by vaccination status.
Results: Among a total of 42 participants and 16 staff, of which 96.6% were fully vaccinated with BNT162b2 mRNA COVID-19 vaccine, 12 symptomatic cases and 13 asymptomatic confirmed cases of COVID-19 were found. The attack rate was 43.1%, with 13 isolates identified as SARS-CoV-2 virus, delta variant. The SAR in unvaccinated and partially vaccinated household members were 27.8% (5/18) and 25.0% (5/20), respectively, while the SAR in fully vaccinated household members was 12.5% (1/8).
Conclusion: We describe a SARS-CoV-2 delta variant outbreak in ADSC with high vaccine coverage rate, characterized by high infection rate, high transmissibility, and low clinical severity. The outbreak proceeded to unvaccinated or partially vaccinated household members, emphasizing the need for immunizing close contacts of high-risk groups.
Keywords: COVID-19; Coronavirus; Effectiveness; SARS-CoV-2; Vaccine.
【저자키워드】 COVID-19, SARS-CoV-2, Vaccine, coronavirus, Effectiveness, 【초록키워드】 coronavirus disease, Coronavirus disease 2019, Vaccine, COVID-19 vaccine, vaccination, mRNA vaccine, variant, SARS-CoV-2 virus, severe acute respiratory syndrome Coronavirus, delta variant, secondary attack rate, BNT162b2, polymerase chain reaction, Coverage, Reverse transcriptase polymerase chain reaction, Transmissibility, Asymptomatic, outbreak, mRNA, attack rate, infection rate, SAR, South Korea, BNT162b2 mRNA COVID-19 vaccine, BNT162b2 mRNA, Clinical severity, close contact, reverse transcriptase, Chain Reaction, mass vaccination, Vaccination Status, confirmed case, acute respiratory syndrome, Participants, acute respiratory syndrome coronavirus, acute respiratory syndrome coronavirus 2, secondary transmission, participant, symptomatic cases, symptomatic case, transcriptase, second, vaccination rate, SARS-CoV-2 delta, isolate, vaccinee, polymerase chain, characterized, calculated, groups, the vaccine, infected case, epidemiologic feature, of BNT162b2, 【제목키워드】 Delta, household, secondary,