Symptoms and severity in vaccinated and unvaccinated patients hospitalised with SARS-CoV-2 delta (B.1.617.2) variant infection

ABSTRACT

BackgroundThe diffusion of the SARS-CoV-2 delta (B.1.617.2) variant and the waning of immune response after primary Covid-19 vaccination favoured the breakthrough SARS-CoV-2 infections in vaccinated subjects. To assess the impact of vaccination, we determined the severity of infection in hospitalised patients according to vaccine status. MethodsWe retrospectively analysed data from patients hospitalised in 10 centres with a SARS-CoV-2 infection (delta variant) from July to November 2021 i) all patients who had completed their primary vaccination at least 14 days before hospital admission; and ii) the same number of completely unvaccinated patients. We assessed the impact of vaccination and other risk factors through logistic regression. FindingsWe included 955 patients (474 vaccinated and 481 unvaccinated). Vaccinated patients were significantly older, more frequently males, and with more comorbidities. They were less often admitted for Covid-19 (59{middle dot}3% vs. 75{middle dot}1%, p<0{middle dot}001), showed fewer lung lesions, and required oxygen less frequently (57{middle dot}5% vs. 73{middle dot}0%, p<0{middle dot}001), at a lower flow (3{middle dot}0 vs. 6{middle dot}0 L/min, p<0{middle dot}001), and for a shorter duration (3 vs. 6 days, p<0{middle dot}001). They less frequently required intensive care unit admission (16{middle dot}2 % vs. 36{middle dot}0 %, p<0{middle dot}001). Mortality at day 28 was not different between the two groups (16{middle dot}7% vs. 12.2%, p=0{middle dot}075), but multivariate logistic regression showed that vaccination significantly decreased the risk of negative outcomes, including mortality, even when considering older patients, and those with comorbidities. ConclusionsAmong patients hospitalised with a delta variant SARS-CoV-2 infection, vaccination was associated with less severe forms, even in the presence of comorbidities.