According to the new report from the Department of Research, Studies, Evaluation and Statistics (DREES), vaccines against Covid-19 would protect 85% against symptomatic forms and 90% against severe forms, but this efficiency decreases over time.
- The vaccine efficacy of a complete vaccine cycle (2 doses) reaches 85% against symptomatic forms and 90% against severe ones.
- However, this efficacy decreases over time against symptomatic forms, hence the need for a 3rd booster dose.
- However, vaccination remains effective against severe forms.
Does getting vaccinated reduce the risk of developing symptoms of Covid-19 and having a severe form of the disease? yes, affirm the new report the Department of Research, Studies, Evaluation and Statistics (DREES).
Published on December 22, it highlights the effectiveness of a complete vaccine cycle to combat symptomatic SARS-CoV-2 infection. The data analyzed are those of the third wave of the Covid-19 epidemic in France, between 1er February and May 31, 2021.
High vaccine efficacy
The results concerning vaccination are very encouraging. They show that even the first dose is 59% effective against symptomatic forms in people aged 50 or over. This efficiency even reaches 85% at the end of a complete vaccination cycle, without a booster dose. Weaker at the start of the vaccination course for people with a comorbidity, the vaccine efficacy also approaches, at the end of the vaccination course, that calculated for all people aged 50 or over.
Similarly, the risk of hospitalization, passage to intensive care and death in hospital is reduced as the vaccine course progresses. From the first dose, the risk of going to critical care is significantly reduced for people aged 50 or over. “In total, by combining a vaccine efficacy of 85% against symptomatic forms at the end of a complete vaccination course with a reduction in the risk of severe forms resulting in a hospital event of 0.67, the vaccine efficacy is would establish 90% against hospitalizations, 94% against passages in critical care and 90% against deaths after a complete vaccination course. The results are very close for people with comorbidity”underlines the DREES in its report.
Effectiveness that decreases over time, except for severe forms
However, this vaccine efficacy is limited in time. The DREES extended the analysis to more recent data by exploring those of the 4and wave, until November 14, 2021. These reveal a very clear reduction in the effectiveness of vaccines against symptomatic forms six months after the last injection, regardless of the age group.
In people aged 50 or over, this vaccine efficacy drops to 57% against symptomatic forms over time and to 39% in people aged 85 or over. According to the DREES, “decrease can be interpreted, under the hypotheses mobilized in the analysis, as the combined effect of the emergence of the delta variant likely to generate immune escape and a decrease in vaccine protection over time”.
However, it is important to note that the vaccines remain effective against severe forms of Covid-19: 84% after the vaccination course has been completed. In the oldest patients, this efficacy against severe forms is 70%.
Hence the importance of carrying out a third dose of vaccine. Seven days after this booster dose, vaccine efficacy returns to very high levels, whether against symptomatic forms or severe forms, without distinction according to age group among those aged 65 or over. It is estimated at 91.5% for people with comorbidity and 92.1% for the entire population aged 50 or over.
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