Association between COVID-19 Primary Vaccination and Severe Disease Caused by SARS-CoV-2 Delta Variant among...

Area of Science:

• * Infectious Diseases
• * Vaccinology
• * Public Health

Background:

• * The Delta variant (B.1.617.2) predominated during the study period, necessitating an evaluation of vaccine effectiveness against severe COVID-19 outcomes.
• * Understanding vaccine effectiveness in hospitalized patients is crucial for informing public health strategies and clinical management.

Purpose of the Study:

• * To assess the effectiveness of a primary COVID-19 vaccination schedule against severe disease progression (ARDS, ICU admission, death) and in-hospital death.
• * To compare the effectiveness of different vaccine brands, including mRNA (mRNA-1273, BNT162b2) and adenovirus-vector (ChAdOx1, Ad26.COV2.S) vaccines.

Main Methods:

• * Retrospective, multicenter cohort study of 2493 hospitalized COVID-19 patients in Belgium (August-November 2021).
• * Mixed effects logistic regression analyses were used to adjust for patient, hospital, and vaccination characteristics.
• * Comparison of severe outcomes between vaccinated and unvaccinated patients, and between different vaccine types.

Main Results:

• * Hospitalized patients with a primary vaccination schedule had significantly lower odds of progressing to severe disease (OR 0.48) and in-hospital death (OR 0.49) compared to unvaccinated individuals.
• * Among vaccinated patients over 75 years, mRNA vaccines and AstraZeneca (AZ) showed similar protection, while Johnson & Johnson (J&J) conferred lower protection.
• * Vaccine effectiveness varied by brand, particularly in older age groups.

Conclusions:

• * A primary COVID-19 vaccination schedule is effective in preventing severe outcomes and in-hospital death among hospitalized patients.
• * Vaccine effectiveness may differ between brands, especially in elderly populations.
• * Continued vaccination efforts are vital for mitigating severe COVID-19 consequences.