This phase 2b clinical study will enroll adult subjects of both sexes with ARDS due to COVID-19 necessitating invasive mechanical ventilation.

The primary objective of the study is the assessment of impact of immune therapy with COVID-19 convalescent plasma on severity of COVID-19.

The secondary objectives is the Impact of immune therapy with COVID-19 convalescent plasma on markers for ARDS due to severe COVID-19 infection; short-term all-cause mortality; time course of ARDS due to severe COVID-19 and assessment of safety and tolerability of immune therapy with COVID-19 convalescent plasma.

As a primary endpoint/variable we will assess change in SOFA score from Baseline Visit to Day 8.

The study design will be prospective, open-label, randomized, controlled and parallel-grouped.

Inclusion Criteria:

1. Male or female subject aged ≥18 years.
2. Estimated BMI ≥19kg/m² to ≤40kg/m².
3. Florid1 SARS-CoV-2 infection confirmed by RT-PCR in tracheo-bronchial secretion sample or pharyngeal swab sample.
4. ARDS with Horovitz index <300mmHg.
5. Necessity of invasive mechanical ventilation.
6. Written informed consent obtained from the subject's legal representative or under such arrangement as is legally acceptable in Germany (
7. Subject's assent if obtainable

Exclusion Criteria:

1. Previous exposure to COVID-19 convalescent plasma.
2. Adverse reaction to plasma proteins in medical history.
3. Interval >72h since endotracheal intubation.
4. Current or imminent necessity of ECMO treatment.
5. Pre-existing COPD GOLD stage 4.
6. Chronic congestive heart failure NYHA ≥3.
7. Pre-existing left ventricular ejection fraction <30%.