(Reuters) – The following is a brief 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.

Convalescent plasma disappoints in Chinese trial

Infusions of antibody-rich blood plasma from people who have recovered from the coronavirus, so-called convalescent plasma, failed to make a difference in a study of hospitalized patients in China, researchers reported on Wednesday in the Journal of the American Medical Association. In a randomized trial involving 103 COVID-19 patients, convalescent plasma made no difference in the time it took to show signs of improvement or in rates of death at 28 days versus a placebo. There were some potentially encouraging results among patients who were “severely ill” but not sick enough to be in the intensive care unit. They recovered roughly five days faster if they got the plasma treatment, and more of them improved within 28 days of starting treatment. The study was somewhat hampered as researchers were not able to enroll as many patients as they had hoped because the epidemic started to come under control in their region, and it was stopped early. Had they been able to enroll as many patients as originally planned, the results might have been different. (bit.ly/3cwmAtt, bit.ly/2MpNWa7)

Hydroxychloroquine fails to protect against infection in key trial

The malaria drug promoted by U.S. President Donald Trump as a treatment for COVID-19 failed to prevent infection in people exposed to the coronavirus, according to data from a large trial released on Wednesday by University of Minnesota researchers. Overall, 821 people who had recently been exposed to the virus or lived in a high-risk household received either hydroxychloroquine or placebo. There was no significant difference in the rate at which participants developed COVID-19. “Our data is pretty clear that for post exposure, this does not really work,” lead researcher Dr. David Boulware told Reuters.

More than 20% of the patients in the trial also took zinc, which had no significant effect. Several trials of hydroxychloroquine have been stopped over concerns about its safety for treating COVID-19 patients, but the new trial found no serious side effects or heart problems with hydroxychloroquine. “I think both sides – one side who is saying ‘This is a dangerous drug’ and the other side that says ‘this works’ – neither is correct,” said Boulware. (; reut.rs/3eQcWn5)

Timing, location of sample may impact coronavirus test results

How well nasal swab tests can identify coronavirus infection depends on how soon they are done after symptoms begin, infectious disease experts advised in a paper titled, “Five Things to Know About Coronavirus Diagnosis Tests” published on Wednesday in the CMAJ medical journal. They also point out that when coronavirus infection is predominantly affecting the lungs, swab samples from the nose and throat are going to be less accurate than samples obtained from sputum and from the windpipe and lungs. “Lower respiratory tract samples may reveal a positive result when nasopharyngeal and oropharyngeal sampling has not,” they write. Furthermore, a positive test does not necessarily indicate how infectious someone may be. “Laboratories report a ‘yes/no’ result and do not regularly report viral load” – the amount of virus in the sample. A positive test long after symptoms have gone away probably is not caused by active virus, they add. For quick “point of care” coronavirus tests, they say, the advantage is a faster answer for the tested person. But those tests have to be processed one at a time, whereas slower testing methods allow for many samples to be processed simultaneously. Finally, they point out, having coronavirus antibodies in your blood – reflecting previous infection – does not equate with immunity. (bit.ly/2Bs0hYV)

More evidence supports masks and social distancing

Social distancing and wearing face masks and eye protection are the best ways to cut the risk of contracting COVID-19, according to the largest review to date of studies on coronavirus disease transmission. Pooling evidence from 172 studies in 16 countries, researchers found frequent handwashing and good hygiene are also critical – though even all those measures combined cannot provide full protection. Much of the data were from epidemics caused by the SARS and MERS viruses in previous years, so the researchers admit the findings may have some limitations for the current pandemic. Still, they wrote on Tuesday in The Lancet medical journal, policy makers around the world need to “promptly and adequately address” shortages of face masks and eye protection. “For healthcare workers and administrators, our findings suggest that N95 respirators might be more strongly associated with protection from viral transmission than surgical masks,” but both of those are more protective than single-layer masks, the said. “Eye protection might also add substantial protection.” For the general public, “face masks are associated with protection, even in non-healthcare settings, with either disposable surgical masks or reusable 12- to 16-layer cotton ones.” (bit.ly/2AFI6OX; reut.rs/2XrQBX2)

U.S. emergency department visits plummet during pandemic

U.S. emergency departments may be packed with coronavirus patients, but the number of people coming in for other reasons has plummeted, a U.S. study confirms. Researchers with the U.S. National Syndromic Surveillance Program reported on Wednesday that compared to the same period last year, emergency department visits between March 29 and April 25 this year were down 42%, from 2.1 million per week to 1.2 million a week – even while the proportion of infectious disease-related visits was four times higher than a year earlier. Among the many conditions U.S. emergency departments saw less often from January through May this year were chest pain, heart attacks, ear infections, abdominal pain, muscle pain, high blood pressure, urinary tract infections, and asthma. The authors of the study, published in the U.S. Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report, warn that declines in visits for serious conditions could result in complications or deaths. They say hospitals need to address patients’ fears of coronavirus exposure in the emergency department by screening everyone for COVID-19 symptoms and by maintaining separate, well-ventilated triage areas for patients with and without signs and symptoms of the virus. Also, they say, health systems should “reinforce the importance of immediately seeking care for serious conditions” and expand access to phone lines and virtual visits where patients can get guidance as to whether they need to go to an emergency room. (bit.ly/2zXOy42; reut.rs/36UPeTV)