Given the current limited treatments available for COVID-19, one area of interest has been convalescent or plasma therapy, which represents a form of passive immunity and has been successfully used to treat other viral infections.
To date only two clinical trials have examined the value of convalescent plasma therapy (CP) in patients with COVID-19 though both were stopped early and did not appear to show any significant benefit. Researchers from the Indian Council of Medical Research have undertaken a randomised trial in over 400 patients but the results also suggest that CP is of limited value. The study recruited 464 adult patients (aged 18 and over) with a median age of 52 years (75% male) from 39 public and private hospitals across India who were admitted to hospital with confirmed moderate COVID-19, based on a positive PCR test. Included patients had a partial pressure of oxygen in arterial blood/fraction of inspired oxygen (Pa02/FiO2) ratio between 200mmHg and 300mmHg, or a respiratory rate of more than 24/minute and an oxygen saturation < 93%. Eligible CP donors were required to have had a PCT positive test for COVID-19 and symptom resolution for 28 consecutive days before donation or a 14-day period which included two negative PCR tests collected 24 hours apart.
Patients were randomised to either CP and best standard of care (intervention group) or care lone (the control group) and intervention patients received two doses of 200ml CP transfused 24 hours apart. The primary outcome as a composite of progression to severe disease Pa02/FiO2 ratio < 100mmHg, anytime within 28 days of enrolment or mortality at 28 days.
Progression to severe disease occurred in 19% vs 18% (intervention vs control) and 28 day mortality occurred in 15% vs 14% (intervention vs control) of patients. There was a statistically significant higher proportion of patients receiving CP with a resolution of shortness of breath after 7 days (76% vs 66%) and fatigue (73% vs 60%), there was no difference for fever or cough. In addition, significantly more patients (68% vs 55%) had a negative PCR test at day 7. The authors concluded that as a treatment for COVID-19, CP appeared to be of limited value.
Agarwal A et al. Convalescent plasma in the management of moderate covid-19 in adults in India: open label phase II multicentre randomised controlled trial (PLACID Trial). BMJ 2020;371:m3939.