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.

Oxygen level while walking identifies at-risk patients

It can be helpful to assess blood oxygen levels in patients when they are walking if that level is normal when they are sitting, a new study suggests. A low level of oxygen in the blood, or hypoxia, contributes to shortness of breath and worsening illness in patients with COVID-19. At 10 Chicago-area hospitals, doctors studied 531 COVID-19 patients whose blood oxygen levels were normal at rest.

Roughly one in four developed hypoxia when they got up and walked. These individuals were nearly five times more likely to eventually need basic oxygen support and nearly eight times more likely to need advanced oxygen therapy, compared to patients whose blood oxygen levels held steady while walking.

The drop in blood oxygen levels while walking could be detected an average of 12 hours before patients required extra oxygen, researchers found. So-called ambulatory hypoxia "may serve as an early, non-invasive physiologic marker for the likelihood of developing moderate to severe disease and help clinicians triage patients and initiate earlier interventions," the researchers proposed in a paper posted on Thursday on medRxiv ahead of peer review. 

Cancer patients should get vaccine priority

Cancer patients who get COVID-19 are at high risk for poor outcomes and should be considered for priority access to coronavirus vaccines, according to The American Association for Cancer Research COVID-19 and Cancer Task Force. The task force reviewed available data on fatality rates of patients with cancer who developed COVID-19 and based their recommendation on 28 publications.

Their position paper was published on Saturday in the journal Cancer Discovery. A separate Italian study reiterated that fear of infection should not be a reason to delay cancer treatments. Among nearly 60,000 cancer patients treated early this year in Italy, fewer than 1% developed COVID-19, they reported on Thursday in JAMA Oncology.

Early reports from China indicated a much higher risk of contracting COVID-19 among patients getting cancer therapy, Dr. Carlo Aschele of Ospedale Sant'Andrea in La Spezia told Reuters. "In Italy, oncologists, and patients as well, were terrified, expecting to face a huge amount of infections and death, particularly among patients receiving chemo or immunotherapy," he said. The reassuring results will allow oncologists and patients to make informed decisions regarding antitumor treatment during this pandemic, he added. 

EU regulators urge caution for vaccines, treatments in pregnant women

The European Medicines Agency said on Monday that the COVID-19 vaccine developed by Pfizer Inc and BioNTech SE should only be given during pregnancy "on a case by case basis" because there are not enough data yet on the potential risks to pregnant women. The U.S. Centers for Disease Control and Prevention (CDC) had already acknowledged the issue on its website. It advises that "getting vaccinated is a personal choice for people who are pregnant."

There is also a lack of data for COVID-19 treatments in pregnant women, according to a paper published on Wednesday in The Lancet Global Health. Researchers who reviewed clinical trial registries found that of 722 COVID-19 treatment studies, 538 (75%) specifically excluded pregnant women.

"Without explicit and proactive efforts to recruit and retain pregnant women in therapeutic trials for COVID-19, expectant mothers will suffer from having fewer medical options available to them, because we are not including them in clinical trials," coauthor Dr. Melanie Taylor from the World Health Organization and CDC said in a statement. "There is a very real possibility that treatment (for COVID-19) could become approved ... without evidence-based guidance for use in pregnant women." 

Low reinfection risk for those who test positive for antibodies

A study of more than three million people adds to evidence that people with COVID-19 antibodies have a significantly lower risk of future infection with the new coronavirus. Working with healthcare data analytics companies HealthVerity and Action, as well as commercial labs Quest Diagnostics and LabCorp, researchers at the U.S. National Cancer Institute (NCI) had access to results of more than 50% of commercial COVID-19 antibody tests conducted in the United States through August.

Overall, 11.6% of the tests were antibody-positive. When researchers looked at study subjects who returned to the labs for repeated tests, they found people who were antibody-positive on the first test had a roughly 10-fold lower risk of having evidence of new infection compared to people with a negative first test. "This finding suggests that people who have a positive antibody test result ... have significant immunity to SARS-CoV-2 and are at lower risk for future infection," said the NCI's Dr. Norman Sharpless. His team's report was posted on medRxiv on Sunday ahead of peer review.