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.

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 / Fabiani, Massimo; Puopolo, Maria; Filia, Antonietta; Sacco, Chiara; Mateo-Urdiales, Alberto; Spila Alegiani, Stefania; Del Manso, Martina; D'Ancona, Fortunato; Vescio, Fenicia; Bressi, Marco; Petrone, Daniele; Spuri, Matteo; Rota, Maria Cristina; Massari, Marco; Da Cas, Roberto; Morciano, Cristina; Stefanelli, Paola; Bella, Antonino; Tallon, Marco; Proietti, Valeria; Siddu, Andrea; Battilomo, Serena; Palamara, Anna Teresa; Popoli, Patrizia; Brusaferro, Silvio; Rezza, Giovanni; Riccardo, Flavia; Menniti Ippolito, Francesca; Pezzotti, Patrizio. - In: EXPERT REVIEW OF VACCINES. - ISSN 1744-8395. - (2022). [10.1080/14760584.2022.2064280]

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

Petrone, Daniele;Spuri, Matteo;Palamara, Anna Teresa;
2022

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.
2022
covid-19; italy; sars-cov-2 infection; booster dose; delta variant; vaccine effectiveness
01 Pubblicazione su rivista::01a Articolo in rivista
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 / Fabiani, Massimo; Puopolo, Maria; Filia, Antonietta; Sacco, Chiara; Mateo-Urdiales, Alberto; Spila Alegiani, Stefania; Del Manso, Martina; D'Ancona, Fortunato; Vescio, Fenicia; Bressi, Marco; Petrone, Daniele; Spuri, Matteo; Rota, Maria Cristina; Massari, Marco; Da Cas, Roberto; Morciano, Cristina; Stefanelli, Paola; Bella, Antonino; Tallon, Marco; Proietti, Valeria; Siddu, Andrea; Battilomo, Serena; Palamara, Anna Teresa; Popoli, Patrizia; Brusaferro, Silvio; Rezza, Giovanni; Riccardo, Flavia; Menniti Ippolito, Francesca; Pezzotti, Patrizio. - In: EXPERT REVIEW OF VACCINES. - ISSN 1744-8395. - (2022). [10.1080/14760584.2022.2064280]
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