SARS-CoV-2 arrived in Washington State somewhere between late January and early February 2020, sparking rapid community transmission of the virus that went undetected for several weeks before this community spread became evident, prompting a change in testing criteria to emphasize individuals with no travel history. That's the scenario proposed by Trevor Bedford and colleagues after their analysis of the genetic sequences of 455 SARS-CoV-2 viruses from the Washington State outbreak collected between January 19 and March 15, 2020.

Using public transportation, visiting a place of worship, or otherwise traveling from the home is associated with a significantly higher likelihood of testing positive with the coronavirus SARS-CoV-2, while practicing strict social distancing is associated with a markedly lower likelihood, suggests a study from researchers at the Johns Hopkins Bloomberg School of Public Health.

Early findings from researchers at Children's Hospital of Philadelphia (CHOP) show that convalescent plasma appears to be a safe and possibly effective treatment for children with life-threatening cases of COVID-19. The results were published online Friday by the journal Pediatric Blood and Cancer.

Results from two early-phase Russian non-randomised vaccine trials (Sputnik V) in a total of 76 people are published today in The Lancet, finding that two formulations of a two-part vaccine have a good safety profile with no serious adverse events detected over 42 days, and induce antibody responses in all participants within 21 days.

In a retrospective study of patients tested for COVID-19, researchers at the University of Chicago Medicine found an association between vitamin D deficiency and the likelihood of becoming infected with the coronavirus.

"Vitamin D is important to the function of the immune system and vitamin D supplements have previously been shown to lower the risk of viral respiratory tract infections," said David Meltzer, MD, PhD, Chief of Hospital Medicine at UChicago Medicine and lead author of the study.

A new international study published today has shown that treating critically ill patients with COVID-19 with the steroid hydrocortisone improves their chances of recovery.

The study, led in the UK by Professor Anthony Gordon from Imperial College London with collaborators from the Intensive Care National Audit & Research Centre, found that patients receiving intensive care who were treated with a regular fixed dose of the steroid hydrocortisone for seven days had a better chance of recovery, compared with the patients who were not treated with the steroid.

On March 28, the Food and Drug Administration (FDA) exercised its Emergency Use Authorization (EUA) authority to allow the use of hydroxychloroquine for the treatment of COVID-19. On June 15, after a number of studies failed to find positive effects, the agency revoked this authorization. This chain of events raises questions about the speed, rigor and potential politicization of the authorization process. These actions also may have hurt the FDA's credibility and the public's trust in the agency, which could decrease the public's confidence in and adoption of eventual COVID-19 vaccines.