Outcomes of COVID-19 Infection in People Previously Vaccinated Against Influenza: Population-Based Cohort Study Using Primary Health Care Electronic Records.

BACKGROUND: A possible link between influenza immunization and susceptibility to the complications of COVID-19 infection has been previously suggested owing to a boost in the immunity against SARS-CoV-2. OBJECTIVE: This study aimed to investigate whether individuals with COVID-19 could have benefited from vaccination against influenza. We hypothesized that the immunity resulting from the previous influenza vaccination would boost part of the immunity against SARS-CoV-2. METHODS: We performed a population-based cohort study including all patients with COVID-19 with registered entries in the primary health care (PHC) electronic records during the first wave of the COVID-19 pandemic (March 1 to June 30, 2020) in Catalonia, Spain. We compared individuals who took an influenza vaccine before being infected with COVID-19, with those who had not taken one. Data were obtained from Information System for Research in Primary Care, capturing PHC information of 5.8 million people from Catalonia. The main outcomes assessed during follow-up were a diagnosis of pneumonia, hospital admission, and mortality. RESULTS: We included 309,039 individuals with COVID-19 and compared them on the basis of their influenza immunization status, with 114,181 (36.9%) having been vaccinated at least once and 194,858 (63.1%) having never been vaccinated. In total, 21,721 (19%) vaccinated individuals and 11,000 (5.7%) unvaccinated individuals had at least one of their outcomes assessed. Those vaccinated against influenza at any time (odds ratio [OR] 1.14, 95% CI 1.10-1.19), recently (OR 1.13, 95% CI 1.10-1.18), or recurrently (OR 1.10, 95% CI 1.05-1.15) before being infected with COVID-19 had a higher risk of presenting at least one of the outcomes than did unvaccinated individuals. When we excluded people living in long-term care facilities, the results were similar. CONCLUSIONS: We could not establish a protective role of the immunity conferred by the influenza vaccine on the outcomes of COVID-19 infection, as the risk of COVID-19 complications was higher in vaccinated than in unvaccinated individuals. Our results correspond to the first wave of the COVID-19 pandemic, where more complications and mortalities due to COVID-19 had occurred. Despite that, our study adds more evidence for the analysis of a possible link between the quality of immunity and COVID-19 outcomes, particularly in the PHC setting.

Antidiabetic treatment and COVID-19 Outcomes: A population-based cohort study in primary health care in Catalonia during the first wave of the pandemic.

AIMS: To analyse if antidiabetic treatment was associated with better COVID-19 outcomes in type 2 diabetic patients, measured by hospital admission and mortality rates as severe outcomes. METHODS: Cohort study including COVID-19 patients registered in the Primary Care electronic records, in March-June 2020, comparing exposed to metformin in monotherapy with exposed to any other antidiabetic. DATA SOURCE: SIDIAP (Information System for Research in Primary Care), which captures clinical information of 5,8 million people from Catalonia, Spain. RESULTS: We included 31,006 diabetic patients infected with COVID-19, 43.7% previously exposed to metformin, 45.5% of them in monotherapy. 16.4% were admitted to hospital and 15.1% died. Users of insulin in monotherapy (OR 1.29, 95% CI 1.11-1.50), combined with metformin (OR 1.38, 1.13-1.69) or IDPP4 alone (OR 1.29, 1.03-1.63) had higher risk of severe outcomes than those in metformin monotherapy. Users of any insulin (OR 1.61, 1.32-1.97) or combined with metformin (OR 1.69, 1.30-2.20) had a higher risk of mortality. CONCLUSIONS: Patients receiving metformin monotherapy in our study showed a lower risk of hospitalization and death in comparison to those treated with other frequent antidiabetic agents. We cannot distinguish if better outcomes are related with the antidiabetic therapy or with other factors, such as metabolic control or interventions applied during the hospital admission.