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. 2022 Dec:4:100076.
doi: 10.1016/j.gloepi.2022.100076. Epub 2022 May 27.

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

Milena Suarez Castillo  1   2 , Hamid Khaoua  1 , Noémie Courtejoie  1
Affiliations

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

Milena Suarez Castillo et al. Glob Epidemiol. 2022 Dec.

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.

Keywords: Booster; COVID-19; Effectiveness; Real-world estimates; SARS-CoV-2; Test-negative design; Vaccine.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Distribution of dates of receipt for the first and second vaccine doses in control and cases, by age-group. Abbreviations: Sympto+ (cases): Symptomatic individuals with a laboratory confirmed SARS-CoV-2 infection (cases). Sympto- (controls): Individuals with symptoms non-related to SARS-CoV-2 infection
Fig. 2
Fig. 2
Covid-19 vaccine effectiveness against symptomatic infections and hospitalizations among persons aged 50 years or over, according to the time elapsed since the receipt of each vaccine dose, data collected from January 1st to December 12, 2021 Abbreviations: D1: First vaccine dose. D2: Second vaccine dose. DB: Booster dose. M: Month. S+: Symptomatic infection. H: Hospitalization. VE: Vaccine effectiveness. The numbers in the x-axis indicate the time (in days or months) elapsed since the receipt of the dose of interest. Precisely, thresholds used to define month intervals are 31–62, 63–90, 91–120, 121–150, 151–182, >182 in days
Fig. 3
Fig. 3
Risk reduction against Covid-19 severe outcomes (hospitalizations, ICU admissions and inpatient deaths) among persons aged 50 years or over, according to the time elapsed since the receipt of each vaccine dose, data collected from January 1st to December 12, 2021 Abbreviations: D1: First vaccine dose. D2: Second vaccine dose. DB: Booster dose. M: Month a The numbers in the x-axis indicate the time (in days or months) elapsed since the receipt of the dose of interest. Precisely, thresholds used to define month intervals are 31–62, 63–90, 91–120, 121–150, 151–182, >182 in days.
Fig. 4
Fig. 4
Covid-19 vaccine effectiveness against symptomatic infections and hospitalizations by age, according to the time elapsed since the receipt of each vaccine dose, data collected from January 1st to December 12, 2021. Abbreviations: D1: First vaccine dose. D2: Second vaccine dose. DB: Booster dose. M: Month. S+: Symptomatic infection. H: Hospitalization. VE: Vaccine effectiveness The numbers in the x-axis indicate the time (in days or months) elapsed since the receipt of the dose of interest. Precisely, thresholds used to define month intervals are 31–62, 63–90, 91–120, 121–150, 151–182, >182 in days.
Fig. 5
Fig. 5
Covid-19 vaccine effectiveness against symptomatic infections and hospitalizations related to various variants of concern, according to the time elapsed since the receipt of each vaccine dose, data collected from January 1st to December 12, 2021. Abbreviations: D1: First vaccine dose. D2: Second vaccine dose. DB: Booster dose. M: Month. S+: Symptomatic infection. H: Hospitalization. VE: Vaccine effectiveness. The numbers in the x-axis indicate the time (in days or months) elapsed since the receipt of the dose of interest. Precisely, thresholds used to define month intervals are 31–62, 63–90, 91–120, 121–150, 151–182, >182 in days
Fig. 6
Fig. 6
Covid-19 vaccine effectiveness against symptomatic infections among persons aged 50 years or over, according to received vaccine and to the time elapsed since the receipt of each vaccine dose, data collected from January 1st to December 12, 2021 Abbreviations: D1: First vaccine dose. D2: Second vaccine dose. DB: Booster dose. The numbers in the x-axis indicate the time (in days or months) elapsed since the receipt of the dose of interest. Precisely, thresholds used to define month intervals are 31–62, 63–90, 91–120, 121–150, 151–182, >182 in days. Cominarty: Primary vaccine course with Cominarty doses only. Spikevax: Primary vaccine course with Spikevax doses only. Vaxzevria: Primary vaccine course with Vaxzevria doses only. Booster dose are relative to mRNA-vaccine Cominarty or Spikevax
Fig. 7
Fig. 7
Risk reduction against Covid-19 severe hospitalizations among persons aged 50 years or over, according to received vaccine and to the time elapsed since the receipt of each vaccine dose, data collected from January 1st to December 12, 2021 Abbreviations: D1: First vaccine dose. D2: Second vaccine dose. DB: Booster dose. The numbers in the x-axis indicate the time (in days or months) elapsed since the receipt of the dose of interest. Precisely, thresholds used to define month intervals are 31–62, 63–90, 91–120, 121–150, 151–182, >182 in days. Cominarty: Primary vaccine course with Cominarty doses only. Spikevax: Primary vaccine course with Spikevax doses only. Vaxzevria: Primary vaccine course with Vaxzevria doses only. Booster dose are relative to mRNA-vaccine Cominarty or Spikevax.There was no hospital admission for the category “DB > 7” with a Spikevax primary course
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