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.
Expert Rev Vaccines
; 21(7): 975-982, 2022 07.
Article
in English
| MEDLINE | ID: covidwho-1778823
ABSTRACT
BACKGROUND:
Consolidated information on the effectiveness of COVID-19 booster vaccination in Europe are scarce. RESEARCH DESIGN ANDMETHODS:
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
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
COVID-19
Type of study:
Experimental Studies
/
Observational study
/
Prognostic study
/
Randomized controlled trials
Topics:
Long Covid
/
Vaccines
/
Variants
Limits:
Humans
Language:
English
Journal:
Expert Rev Vaccines
Journal subject:
Allergy and Immunology
Year:
2022
Document Type:
Article
Affiliation country:
14760584.2022.2064280
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