COVID-19 among undocumented migrants admitted to French intensive care units during the 2020-2021 period: a retrospective nationwide study.

Background: Before the Coronavirus Disease 2019 (COVID-19) pandemic in France, undocumented migrants had a higher risk than general population for being admitted to the intensive care unit (ICU) because of acute respiratory failure or severe infection. Specific data concerning the impact of COVID-19 on undocumented migrants in France are lacking. We aimed to analyze the mortality and respiratory severity of COVID-19 in this specific population. We retrospectively included all undocumented adult migrants admitted in French ICUs from March 2020 through April 2021 using the French nationwide hospital information system (Programme de Médicalisation des Systèmes d'Information). We focused on admissions related to COVID-19. Undocumented migrants were compared to the general population, first in crude analysis, then after matching on age, severity and main comorbidities. The primary outcome was the ICU mortality from COVID-19. Secondary objectives were the incidence of acute respiratory distress syndrome (ARDS), the need for mechanical ventilation (MV), the duration of MV, ICU and hospital stay.

Results: During the study period, the rate of ICU admission among patients hospitalized for COVID-19 was higher for undocumented migrants than for general population (463/1627 (28.5%) vs. 81 813/344 001 (23.8%); p < 0.001). Although ICU mortality was comparable after matching (14.3% for general population vs. 13.3% for undocumented migrants; p = 0.50), the incidence of ARDS was higher among undocumented migrants (odds ratio, confidence interval (OR (CI)) 1.25 (1.06-1.48); p = 0.01). Undocumented migrants needed more frequently invasive MV (OR (CI) 1.2 (1.01-1.42); p = 0.04 than general population. There were no differences between groups concerning duration of MV, ICU and hospital length of stay.

Conclusion: During the first waves of COVID-19 in France, undocumented migrants had a mortality similar to the general population but a higher risk for ICU admission and for developing an ARDS. These results highlight the need for reinforcing prevention and improving primary healthcare access for people in irregular situation.