Convalescent plasma lowers Covid-19 death risk; exposure to common cold may limit disease severity

The following is a brief roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for Covid-19, the illness caused by the virus.

Convalescent plasma lowers Covid-19 death risk

Infusions of antibody-rich blood plasma from people who have recovered from the new coronavirus, known as convalescent plasma, can lower the risk of death for hospitalized Covid-19 patients, according to a pooled analysis of data from eight earlier studies of more than 700 hospitalised patients around the world. Researchers found that mortality rates were roughly 13% in patients who received convalescent plasma versus about 25% for those who did not get the treatment. Convalescent plasma was shown to be safe in an earlier study of 5,000 hospitalized adults with severe or life-threatening Covid-19. In that study, fewer than 1% of patients had any serious adverse effects in the first four hours after transfusion. The current study could not account for differences in factors such as how sick patients were, how much plasma they received, how long they were sick before the received it, and how long doctors followed them afterward. "Given the safety of plasma administration in Covid-19 patients, the results ... provide encouragement for its continued used as a therapy," the researchers write in a report published ahead of peer review.

Exposure to common colds may impact Covid-19 severity

In patients with Covid-19, the immune system's T cells learn to recognize and target the new coronavirus. But some people who were never infected with the virus nonetheless have T cells that also recognize it. Researchers had suspected that in these individuals, past exposure to other coronaviruses, such as those that cause the common cold, had somehow primed their T cells to recognize and attack this new coronavirus (SARS-CoV-2), and new research appears to confirm that. In studies of human blood samples collected well before the new coronavirus was discovered, researchers found T cells that were equally reactive against the new virus and four types of common cold coronaviruses. The strongest T cell responses to the new coronavirus were associated with the spike protein the virus uses to enter human cells. "We knew there was pre-existing reactivity, and this study provides very strong direct molecular evidence that memory T cells can 'see' sequences that are very similar between common cold coronaviruses and SARS-CoV-2," coauthor Alessandro Sette of the La Jolla Institute for Immunology said in a statement. It is plausible to think that previous exposure to common cold viruses might contribute to variations in Covid-19 severity, researchers said on Tuesday in the journal Science. 

Severe Covid-19 may be less deadly in children

Children with Covid-19 rarely become critically ill, and when they do, they tend to have better outcomes than adults, based on early data from an ongoing study. The Critical Coronavirus and Kids Epidemiology (CAKE) study involves 65 pediatric intensive care units in 18 countries. In a paper published on Wednesday in the journal Pediatrics, the study team reported on the first 17 children with severe Covid-19 from 10 hospitals in Chile, Colombia, Italy, Spain and the United States. Most required respiratory support, with nearly half needing to be put on ventilators. Symptoms were varied, with fever, cough and gastrointestinal issues common. Overall, one child died, four developed inflammation of the heart and three remain hospitalized. The investigators hope to have more data soon that will provide additional information on the care and outcomes of these patients, which may become more important as schools reopen around the world. As of now, CAKE has enrolled almost 100 critically ill children "and we are projecting perhaps 100 more by the end of 2020," Dr. Sebastian Gonzalez-Dambrauskas, with the Latin American Pediatric Collaborative Network, told Reuters.