This week's roundup of some of the latest scientific studies on the coronavirus and efforts to find treatments and vaccines for COVID-19 refutes claims that high doses of vitamins can speed up recovery, eases concerns about the U.K. variant and reveals interesting finds in the brain and blood.

UK variant not causing worse illness in children

The coronavirus variant first identified in the U.K. does not cause more severe disease in children than variants circulating earlier in 2020, new data suggests.

Doctors at King's College Hospital in London compared 20 children hospitalized for COVID-19 during the pandemic's first wave and 60 hospitalized during the second wave when most infections were caused by the new variant. While more children were hospitalized in the second wave, "this might be due to the higher prevalence of SARS-CoV-2" at the time, study leader Dr. Atul Gupta said.

The number of adult patients also increased in the second wave, he noted. Hospitalized children in both waves had similar ages, rates of underlying medical conditions, socioeconomic status and other risk factors, the researchers reported in The Lancet Child & Adolescent Health. In both periods, few needed oxygen therapy or mechanical ventilation. Those were actually needed less often in the second wave, Gupta said.

"We have found no evidence of more severe disease having occurred in children and young people during the second wave," he concluded, "suggesting that infection with the B.1.1.7 variant does not result in an appreciably different clinical course" in this age group.

Bone marrow cells travel to brain in some COVID-19 patients

Very large bone marrow cells are showing up in the brains of people who died of COVID-19, which may help explain some of the neurological problems associated with the disease, according to researchers. The cells, called megakaryocytes, normally reside in the bone marrow and make platelets for blood clotting.

"We found that in some patients who died of COVID-19, the capillaries – the smallest blood vessels – contained very large cells called megakaryocytes," study leader David Nauen of Johns Hopkins University told Reuters. "They are so large they could be occluding blood flow through the capillaries and limiting oxygen delivery to the brain, which could impair brain function."

As reported in the journal JAMA Neurology, his team studied brain tissue from 15 patients who died of COVID-19 and found megakaryocytes in five of their brains. "What signaled these cells to leave the bone marrow and travel to the brain is unknown, but COVID-19 causes disruptions of the clotting system, and it's possible this is related," Nauen said.

Protective antibodies detectable in dried blood spots

Researchers at Northwestern University have developed a laboratory test for measuring neutralizing antibodies against the coronavirus that requires only a single drop of blood, collected and dried on filter paper.

"Blood samples can be self-collected at home, and sent to the lab in the mail," said Thomas McDade, whose team described the technique in a report posted on medRxiv ahead of peer review. Currently, to determine if someone has the neutralizing antibodies that protect against the virus that causes COVID-19, blood must be drawn at a clinic or doctor's office and sent for analysis.

The Northwestern test "produces results that are comparable to results from venous blood, and the protocol can be implemented in a short amount of time with widely available laboratory infrastructure," McDade said. "This method allows for large-scale testing of neutralizing antibodies against COVID-19, which may be useful for evaluating the effectiveness of vaccines and the level of protective immunity in the general population."

The researchers have not yet used their test to look for neutralizing antibodies against emerging variants. "We can modify the test for specific variants as needed," McDade said.

Zinc, vitamin C show no benefit in randomized trial

In adults with COVID-19 who were not sick enough to be hospitalized, high doses of zinc or vitamin C, or both, failed to improve their symptoms or speed their recovery, researchers reported in JAMA Network Open.

They randomly assigned 214 patients to 10 days of treatment with either a high dose of zinc, vitamin C, both, or neither. Everyone also received standard supportive treatments from their healthcare providers. There was no significant difference between the groups in the number of days required to reach a 50% reduction in symptoms like fever, cough, shortness of breath, and fatigue. There was also no difference in the number of days until patients no longer had severe symptoms, in need of other prescribed medications, or in rates of hospitalizations and deaths.

Zinc and vitamin C (ascorbic acid) supplements "cannot be recommended" to ease the course of COVID-19 in outpatients, the researchers concluded. "Most consumers of ascorbic acid and zinc are taking significantly lower doses of these supplements, so demonstrating that even high-dose ascorbic acid and zinc had no benefit suggests a clear lack of efficacy," they said. A similar study had found the same outcome for vitamin D.