Older COVID-19 patients who receive high-titer plasma from people who have recovered from the disease are half as likely to develop severe respiratory problems, but only if they receive the infusion within the 72 hours of mild symptoms, an Argentinian study has concluded. In late November, a separate group of Argentine doctors reported that the treatment did not help reduce symptoms or the risk of death in patients with severe COVID pneumonia. But the new study, also reported by the New England Journal of Medicine, shows that the antibodies in the plasma can have a significant impact when given much earlier. While 31% of the 80 patients in the placebo group ultimately developed severe respiratory disease, the rate was 16% among the 80 who received the plasma, a 48% reduction (P=0.03). All of the patients were over 65 and many had underlying health problems that increased their risk of death or serious respiratory problems. None received any other experimental treatment for the novel coronavirus. There were no serious side effects. By reducing the odds of progression of COVID-19 to a severe illness, "this simple and inexpensive intervention can reduce demands on the health care system and may save lives," said the research team led by Dr. Fernando Polack of the non-profit Fundacion Infant in Buenos Aires. "Early infusions of convalescent plasma can provide a bridge to recovery for at-risk patients until vaccines become widely available," they said. Doctors have long suspected that the plasma is useful — it's been used for over a century to help patients with a wide range of infections — but finding the most effective way to use it in the current pandemic has been the challenge. Patients were considered to have severe respiratory disease if their oxygen saturation was below 93% while breathing ambient air, they were breathing at 30 breaths or more per minute, or both. The trial was ended early because the number of COVID-19 cases began to fall to a point where it was going to take many months to enroll enough patients. The research team had originally hoped to have a sample size of 210. The Polack team estimated that only 7 patients needed to be treated to avert one episode of severe respiratory disease. Two patients in the convalescent plasma group died versus 4 in the placebo group, although the difference was not statistically significant. Four of the plasma patients had life-threatening respiratory disease compared with 10 of the placebo patients. The researchers also saw a strong dose effect. When the IgG titer of the plasma was at or above the median concentration of 1:3200, the treatment reduced the risk of severe respiratory disease by 73%. At below-median concentrations, the relative risk reduction was 31%. "Although our trial lacked the statistical power to discern long-term outcomes, the convalescent plasma group appeared to have better outcomes than the placebo group with respect to all secondary end points," the researchers said. "Our findings underscore the need to return to the classic approach of treating acute viral infections early, and they define IgG targets that facilitate donor selection." In other convalescent plasma trials, the patients had been symptomatic for 8 to 30 days. The test was financed by the Bill & Melinda Gates Foundation and the Fundacion Infant Pandemic Fund. —Reuters Staff Source
