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We estimated attack rates of severe acute respiratory syndrome coronavirus 2 Omicron (B.1.1.529) infection among people attending a nightclub and a graduation ball where >95% had at least 2 vaccine doses. Attack rates were 295 of 535 (55.1%) and 102 of 189 (54.0%), respectively (mean, 5 days postevent). At the ball, attack rates increased with time since vaccination: 12.5% among those vaccinated 1-2 months previously and 68.0% among those vaccinated ≥3 months previously; such differences were not found at the nightclub. Recent vaccination prevents Omicron infection, but is time and setting dependent, emphasizing the importance of nonpharmaceutical public health measures in addition to vaccine booster doses to maximize protection in high-risk contexts., Competing Interests: Potential conflicts of interest . The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

There is limited data directly comparing the effectiveness of different COVID-19 vaccines. We compared rates of SARS-CoV-2 Omicron BA.1/2 infection during March to May 2022 in Australian adults who had received one of four COVID-19 vaccines in the last 14–63 days as either a primary course or a booster dose using Cox proportional hazards models adjusting for age and other characteristics. As a primary course, over 2318 person-years and 1033 infections, compared to recipients of BNT162b2 mRNA vaccine, adjusted hazard ratios for SARS-CoV-2 infection were 1.03 (95%CI 0.82–1.30), 1.19 (0.95–1.49), 1.70 (1.46–1.97) for respectively mRNA-1273, ChAdOx-1 nCov-19 and NVX-CoV2373. For the booster dose, over 154,984 person-years and 93,580 infections the respective adjusted hazard ratios compared to BNT162b2 mRNA vaccine were 1.02 (95%CI 1.00–1.04), 1.20 (1.10–1.32), 1.39 (1.20–1.60). Our findings suggest relatively higher effectiveness of ancestral strain mRNA vaccines against SARS-CoV-2 Omicron infection than viral vector and protein subunit vaccines and provide clinical confirmation of immunological data on differences in COVID-19 vaccine performance. [ABSTRACT FROM AUTHOR]

The article focuses on the lower uptake of COVID-19 vaccination among individuals with previous SARS-CoV-2 infection. Topics include the lower coverage of vaccination among infected individuals compared to uninfected individuals, the impact of timing of infection on vaccine uptake, and the need for increased adherence to vaccination recommendations to reduce COVID-19 illness rates.

• In an infection-naiive population older adult population, recent administration of a 3rd COVID-19 vaccine dose reduced the risk of hospitalisation/death from SARS-CoV-2 Omicron variant by 65% compared to dose 2. • Over 6 weeks, one hospitalisation/death was avoided by boosting 192 adults aged 70 + years with a third COVID-19 vaccine dose. We estimate effectiveness of 3 versus 2 vaccine doses against SARS-CoV-2 B.1.1.529 Omicron in a mostly infection-naiive but highly vaccinated Australian population. Cohort study of adults aged 40+ years resident in Sydney followed from 1 January 2022 for SARS-CoV-2 infection and COVID-19 hospitalisation or death using linked immunisation, disease notification and hospitalisation registers. Adjusted hazard ratios (aHR) and corresponding relative vaccine effectiveness (rVE) were estimated comparing 3 to 2 vaccine dose recipients by time since dose receipt, vaccine brand, and prior infection. Absolute risk reductions and numbers needed to boost by age groups were calculated. 2,053,123 infection-naiive individuals (mean age 59 years) were followed for 327,272 person-years for infection and 224,269 person-years for severe outcomes (hospitalisation/death). There were 175,849 infections and 4113 hospitalisations/deaths. Compared to individuals receiving dose 2 within the last 3 months, rVE in dose 3 recipients was 7% (95% CI 5–9%) against infection and 65% (95%CI 61–69%) against hospitalisation/death. Almost all dose 3 recipients had an mRNA vaccine; there was little difference in dose 3 rVE by primary course vaccine brand (ChAdOx1 versus BNT162b2). Over the 6-week follow-up, we estimated one hospitalisation/death was avoided for every 192 adults aged ≥70 years boosted with dose 3 in the infection-naiive cohort. The aHR for hospitalisation/death from Omicron was 0.12 (95 %CI 0.07–0.23) for 2-dose recipients with a prior Delta infection compared with 2-dose recipients with no prior infection. Receipt of a third COVID-19 vaccine dose in adults aged 40 years and above significantly reduced hospitalisations and deaths from SARS-CoV-2 Omicron infections in a primarily infection-naiive population. [ABSTRACT FROM AUTHOR]