This week's roundup of the latest scientific research on the novel coronavirus and efforts to find treatments and vaccines for COVID-19 suggest that while low levels of vitamin D remain linked with a higher risk of COVID-19, high levels do not offer protection. Meanwhile, research has found that the immune system replaces antibody-producing cells with other immune cells to fight the virus in blood cancer patients while another study says that a high percentage of patients who experienced long COVID-19 have air trapped in their lungs.
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.
However, 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-19 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.