Vaccine effectiveness against COVID-19 hospitalization in adults in France: A test negative case control study

BACKGROUND: Measuring vaccine effectiveness (VE) using real-life data is critical to confirm the effectiveness of licensed vaccine, which could strengthen vaccination adherence. METHODS: We measured VE against adult COVID-19 hospitalization in five hospitals in France using a test negative design. We compared the odds of vaccinated patients hospitalized with COVID-19 with the odds of vaccinated patients hospitalized for the same symptoms with a negative test. RESULTS: A total of 853 patients (463 cases and 390 controls) were included, with a total of 170 patients vaccinated (104 with one dose, 65 with two doses, and one with three doses). There were four cases of breakthrough infections, all in immunocompromised patients. The VE was 84.0% (CI(0.95) = [72.6; 90.6]) for one dose and 96.2% (CI(0.95) = [86.8; 98.9]) for two doses. CONCLUSION: Our results confirm the high VE of COVID-19 vaccine in France to prevent hospitalizations due to the alpha variant.