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. 2022 Jul;21(7):975-982.
doi: 10.1080/14760584.2022.2064280. Epub 2022 Apr 15.

Effectiveness of an mRNA vaccine booster dose against SARS-CoV-2 infection and severe COVID-19 in persons aged ≥60 years and other high-risk groups during predominant circulation of the delta variant in Italy, 19 July to 12 December 2021

Massimo Fabiani  1 , Maria Puopolo  2 , Antonietta Filia  1 , Chiara Sacco  1 , Alberto Mateo-Urdiales  1 , Stefania Spila Alegiani  3 , Martina Del Manso  1 , Fortunato D'Ancona  1 , Fenicia Vescio  1 , Marco Bressi  1 , Daniele Petrone  1 , Matteo Spuri  1 , Maria Cristina Rota  1 , Marco Massari  3 , Roberto Da Cas  3 , Cristina Morciano  3 , Paola Stefanelli  1 , Antonino Bella  1 , Marco Tallon  4 , Valeria Proietti  5 , Andrea Siddu  6 , Serena Battilomo  5 , Anna Teresa Palamara  1 , Patrizia Popoli  3 , Silvio Brusaferro  7 , Giovanni Rezza  6 , Flavia Riccardo  1 , Francesca Menniti Ippolito  3 , Patrizio Pezzotti  1
Affiliations

Effectiveness of an mRNA vaccine booster dose against SARS-CoV-2 infection and severe COVID-19 in persons aged ≥60 years and other high-risk groups during predominant circulation of the delta variant in Italy, 19 July to 12 December 2021

Massimo Fabiani et al. Expert Rev Vaccines. 2022 Jul.

Abstract

Background: Consolidated information on the effectiveness of COVID-19 booster vaccination in Europe are scarce.

Research design and methods: We assessed the effectiveness of a booster dose of an mRNA vaccine against any SARS-CoV-2 infection (symptomatic or asymptomatic) and severe COVID-19 (hospitalization or death) after over two months from administration among priority target groups (n = 18,524,568) during predominant circulation of the Delta variant in Italy (July-December 2021).

Results: Vaccine effectiveness (VE) against SARS-CoV-2 infection and, to a lesser extent, against severe COVID-19, among people ≥60 years and other high-risk groups (i.e. healthcare workers, residents in long-term-care facilities, and persons with comorbidities or immunocompromised), peaked in the time-interval 3-13 weeks (VE against infection = 67.2%, 95% confidence interval (CI): 62.5-71.3; VE against severe disease = 89.5%, 95% CI: 86.1-92.0) and then declined, waning 26 weeks after full primary vaccination (VE against infection = 12.2%, 95% CI: -4.7-26.4; VE against severe disease = 65.3%, 95% CI: 50.3-75.8). After 3-10 weeks from the administration of a booster dose, VE against infection and severe disease increased to 76.1% (95% CI: 70.4-80.7) and 93.0% (95% CI: 90.2-95.0), respectively.

Conclusions: These results support the ongoing vaccination campaign in Italy, where the administration of a booster dose four months after completion of primary vaccination is recommended.

Keywords: COVID-19; Italy; SARS-CoV-2 infection; booster dose; delta variant; vaccine effectiveness.

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Figures

Figure 1.
Figure 1.
Timeline of the periods of selection and event ascertainment in the population under study, Italy, 27 December 2020 to 12 January 2022 (n = 18,524,568).
Figure 2.
Figure 2.
Selection of the population included in the analysis, Italy, 19 July to 28 November 2021 (n = 18,524,568).a i.e. healthcare workers, residents in long-term-care facilities, and persons with comorbidities or immunocompromised.
See this image and copyright information in PMC

References

    1. Italian Ministry of Health . Piano vaccini anti-Covid-19. [cited 2022 Jan 31]. Available from: https://www.salute.gov.it/portale/nuovocoronavirus/dettaglioContenutiNuo...
    1. Veneti L, Bøås H, Bråthen Kristoffersen A, et al. Reduced risk of hospitalisation among reported COVID-19 cases infected with the SARS-CoV-2 omicron BA.1 variant compared with the delta variant, Norway, December 2021 to January 2022. Euro Surveill. 2022;27(4): ii=2200077. - PMC - PubMed

    2. •• This is a published study conducted in Europe evaluating the effectiveness of a booster dose of a COVID-19 vaccine against hospitalization due to infection with the Delta variant of SARS-CoV-2.

    1. Andrews N, Stowe J, Kirsebom F, et al. Effectiveness of COVID-19 booster vaccines against covid-19 related symptoms, hospitalisation and death in England. Nat Med. 2022. 10.1038/s41591-022-01699-1. online ahead of print. - DOI - PMC - PubMed
    1. Berec L, Šmíd M, Přibylová L, et al.Real-life protection provided by vaccination, booster doses and previous infection against covid-19 infection, hospitalisation or death over time in the Czech Republic: a whole country retrospective view. medRxiv. 2021. 2021.12.10.21267590 2021.12.10.21267590: Preprint10.1101/2021.12.10.21267590 - DOI

    2. • Although not yet peer-reviewed, this is one of the few studies conducted in Europe that has evaluated the effectiveness of a booster dose of a COVID-19 vaccine against infection and severe disease due to the Delta variant

    1. Holm Hansen C, Shelde AB, Moustsen-Helm IR, et al. Vaccine effectiveness against SARS-CoV-2 infection with the omicron or delta variants following a two-dose or booster BNT162b2 or mRNA-1273 vaccination series: a Danish cohort study. medRxiv. 2021. 2021.12.20.21267966 2021.12.20.21267966: Preprint 10.1101/2021.12.20.21267966 - DOI

    2. • Although not yet peer-reviewed, this is one of the few studies conducted in Europe that has evaluated the effectiveness of a booster dose of a COVID-19 vaccine against infection due to the Delta variant

Supplementary concepts