Dataset Information

Vaccine effectiveness and duration of protection against symptomatic infections and severe Covid-19 outcomes in adults aged 50 years and over, France, January to mid-December 2021.

ABSTRACT:

Background

SARS-CoV-2 continues to spread despite fast vaccine rollout, which could be attributed to waning immunity or to a reduced protection against some variants. A thorough characterization of vaccine protection and its duration in time is needed to inform vaccination policies and enhance public trust.

Methods

We linked three national databases with exhaustive information on screening, vaccination and hospitalizations in France from January 1st to December 12, 2021. We performed a two-step analysis to estimate vaccine effectiveness against severe outcomes of Covid-19 (requiring hospitalization) in people aged 50 years or over, combining: (i) a test-negative case-control design to assess vaccine effectiveness against symptomatic infections; and (ii) a survival analysis to assess the additional protection against severe outcomes (hospitalizations, ICU admissions and inpatient deaths) in infected individuals.

Findings

We found a high vaccine effectiveness in people aged 50 years or more, reaching 82% against symptomatic infections and 94% against hospitalizations, after a full vaccination scheme with the Covid-19 vaccines used in France.Vaccine effectiveness against symptomatic infections decreased over time, dropping to 53% after six months, but remained high against severe outcomes (90% after six months). The booster dose allowed restoring protection levels above 90% against symptomatic infections. Vaccine protection and its evolution in time, showed little difference against the variants that circulated prior to December 2021 in France, including the Delta variant.

Interpretation

Though vaccine immunity decreases over time, vaccination remains crucial to provide individual protection against severe outcomes requiring hospitalization. This decline can be reversed by the receipt of a booster dose.

SUBMITTER: Suarez Castillo M

PROVIDER: S-EPMC9135646 | biostudies-literature | 2022 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Vaccine effectiveness and duration of protection against symptomatic infections and severe Covid-19 outcomes in adults aged 50 years and over, France, January to mid-December 2021.

Suarez Castillo Milena M Khaoua Hamid H Courtejoie Noémie N

Global epidemiology 20220527

<h4>Background</h4>SARS-CoV-2 continues to spread despite fast vaccine rollout, which could be attributed to waning immunity or to a reduced protection against some variants. A thorough characterization of vaccine protection and its duration in time is needed to inform vaccination policies and enhance public trust.<h4>Methods</h4>We linked three national databases with exhaustive information on screening, vaccination and hospitalizations in France from January 1st to December 12, 2021. We perfor ...[more]

PMID: 35662871

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Project description:The emergence of SARS-CoV-2 variants calls for continuous monitoring of vaccine effectiveness (VE). We estimated the absolute effectiveness of complete 2-dose primary vaccination and booster vaccination with COVID-19 mRNA vaccines, and the duration of protection against Delta and Omicron BA.1 symptomatic infection and severe outcomes. French residents aged ≥50 years, who presented with SARS-CoV-2-like symptoms and tested for SARS-CoV-2 between June 6, 2021 and February 10, 2022 were included. A test-negative study was conducted to estimate VE against symptomatic infection, using conditional logistic regression models. Cox proportional hazard regressions were performed to assess additional protection against severe COVID-19 outcomes (any hospitalization, and intensive care units [ICU] admission or in-hospital death). In total, 273732 cases and 735 919 controls were included. VE against symptomatic infection after 2-doses vaccination was 86% (95% CI: 75-92%) for Delta and 70% (58-79%) for Omicron, 7-30 days post vaccination. Protection waned over time, reaching 60% (57-63%) against Delta and 20% (16.-24%) for Omicron BA.1 > 120 days after vaccination. The booster dose fully restored protection against symtpomatic Delta infection (95% [81-99%]) but only partially against symptomatic Omicron BA.1 infection (63% [59-67%]). VE against Delta-related severe outcomes was above 95% with 2 doses, and persisted for at least four months. Protection against any Omicron BA.1-hospitalization was 92% (65%-99%) at 8-30 days, and 82% (67%-91%) > 120 days from the second dose. Against BA.1 ICU admission or in-patient death, VE stood at 98% (0-100%) at 8-30 days, and was 90% (40-99%) > 120 days from the second dose. Protection confered by mRNA vaccines against severe disease caused by either Delta or Omicron BA.1 appeared high and sustained over time. Protection against symptomatic diseases after 2 doses decreased rapidly, especially against Omicron BA.1. A booster dose restored high protection against Delta but only a partial one against Omicron BA.1.

Dataset Information

Vaccine effectiveness and duration of protection against symptomatic infections and severe Covid-19 outcomes in adults aged 50 years and over, France, January to mid-December 2021.

Background

Methods

Findings

Interpretation

Publications

Vaccine effectiveness and duration of protection against symptomatic infections and severe Covid-19 outcomes in adults aged 50 years and over, France, January to mid-December 2021.

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