THE following is a 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.

Coronavirus does not threaten U.S. blood supply

Current guidelines for screening U.S. blood donors for symptoms of COVID-19 and for a history of recent infections are effectively protecting the blood supply from contamination with the new coronavirus, researchers say. In a study conducted for the National Institutes of Health, researchers tested nearly 18,000 "minipools" of blood samples – that is, blood samples pooled from total of roughly 258,000 donors from across the country. Only three minipools contained genetic material from the virus, according to a report published in the journal Transfusion. In all three, the viral levels were low. In the one minipool that could be tested for infectivity, the virus material was noninfectious, the researchers said. "Other studies have shown that in rare cases where a blood sample tested positive, transmission by blood transfusion has not occurred," coauthor Sonia Bakkour of the University of California, San Francisco, said in a statement. "Therefore, it appears safe to receive blood as a transfusion recipient and to keep donating blood, without fear of transmitting COVID-19 as long as current screenings are used." 

High vitamin D levels do not protect against COVID-19

Low levels of vitamin D have been tied to higher risks for COVID-19 and more severe illness, although no studies have proved that vitamin D deficiency is actually to blame. A study published on Tuesday in PLoS Medicine suggests that boosting vitamin D levels with supplements would not help. Researchers studied more than 1.2 million people of European ancestry from 11 countries, some of whom had genetic variants that result in naturally higher levels of vitamin D. People with these variants did not have a lower risk for coronavirus infection, hospitalization, or severe COVID-19, the researchers reported. Their results suggest that boosting vitamin D levels in deficient people probably would not help combat the coronavirus, and they do not believe randomized trials testing vitamin D supplementation would be worthwhile. Other experts, however, would still like to see such trials, especially in people of African and other non-European ancestries. 

Immune system workaround helps blood cancer patients with COVID-19

In blood cancer patients who lack antibody-producing cells, other immune cells can compensate to help fight the coronavirus, new research shows. People with blood cancers – such as leukemia, lymphoma, and myeloma - often lack antibody-making immune cells called B cells, particularly after treatment with certain medications. Without enough B cells and antibodies, they are at risk for severe COVID-19. But other immune cells, called T cells, learn to recognize and attack the virus, according to a report published in Nature Medicine. Blood cancer patients in the study were more likely to die from COVID-19 than patients with solid tumors or without cancer. But among the blood cancer patients, those with higher levels of CD8 T cells were more than three times more likely to survive than those with lower levels of CD8 T cells. The authors speculate that CD8 T cell responses to COVID-19 vaccines might protect blood cancer patients even if they do not have typical antibody responses. "This work can help us advise patients while we wait for more vaccine specific studies," said co-author Dr. Erin Bange of the University of Pennsylvania in a statement. While patients' vaccine response "likely will not be as robust as their friends/family who don't have blood cancers, it is still ... potentially lifesaving," Bange added.

In some long COVID cases, air gets trapped in lungs

Some COVID-19 survivors with persistent breathing symptoms have a condition called "air trapping," in which inhaled air gets stuck in the small airways of the lung and cannot be exhaled. Researchers studied 100 COVID-19 survivors who were still having respiratory problems, like coughs and shortness of breath, an average of more than two months after their diagnosis. Overall, 33 had been hospitalized, including 16 who had needed intensive care. The amount of lung area showing so-called ground-glass opacities on imaging studies – a typical sign of lung damage from COVID-19 – was higher in the hospitalized group than in those with milder disease, and it was even higher in patients who had required intensive care. COVID-19 severity made little difference in the average percentage of lung affected by air trapping, however. It was 25.4% in patients not hospitalized, 34.5% in those who were hospitalized without intensive care, and 27.2% in patients who had been critically ill. By comparison, that proportion was 7.3% in a group of healthy volunteers. The air trapping was largely confined to patients' narrowest airway passages, according to a report posted on Saturday on medRxiv ahead of peer review. "The long-term consequences" of these patients' small airways disease "are not known," the authors said.