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.

Long-term health problems seen in low-risk COVID-19 patients

Young, healthy adults with COVID-19 who do not require hospitalization are still at risk for long-term health problems, Oxford University researchers found. They studied 201 recovering UK patients with an average age of 44, more than 90% of whom did not have risk factors such as diabetes, high blood pressure, or heart disease. Only 18% had been sick enough to be hospitalized.

At an average of 140 days after their symptoms began, 98% were still fatigued, 92% had heart and lung symptoms, 88% had muscle aches, 87% had breathlessness, 83% headaches, and 73% gastrointestinal symptoms. Organ damage was more common among those who had been hospitalized. But it was not limited to that group as 66% of the patients had impairment of at least one organ.

Magnetic resonance imaging (MRI) scans showed mild damage to lungs in 33%, heart in 32%, pancreas in 17%, kidneys in 12%, liver in 10% and spleen in 6%. The researchers say their study, posted on Friday on medRxiv ahead of peer review, cannot prove the virus caused these later issues. But it does suggest long-term monitoring of organ function will be necessary even in relatively low-risk patients. 

Flu shot may help protect against COVID-19

Flu vaccines may help the body defend itself against COVID-19, according to a Dutch study that found hospital workers who got a flu shot last winter were less likely to become infected with the new coronavirus. In test tube experiments, the researchers saw that last winter's flu vaccine could prime healthy cells to respond more effectively not just to the flu, but also to the new coronavirus.

When they analyzed COVID-19 rates among staff at their hospital, they found the number of infections was 39% lower among those who had gotten a flu vaccine. "These data, combined with similar recent independent reports, argue for a possible beneficial effect of influenza vaccination against both influenza and COVID-19," the researchers say. "This could mean that the flu vaccine could offer partial protection against both infections this winter."

They posted their report on medRxiv on Friday ahead of peer review. "We thought it was important to publish these results already because the flu shot is made available to a large group of people," study leader Mihai Netea of Radboud University Medical Center said in a news release. 

Pandemic increases need for strength training by elderly

Older people "urgently" need to be doing resistance exercises, also known as strength training, during the pandemic, to counteract the effects of physical inactivity and to make sure they retain at least the same level of muscle function they had prior to lockdowns and stay-at-home orders, doctors advise.

Social distancing measures cause "greater time at home and consequently a reduction in general physical activity and an increase in sedentary time, which is harmful to older people," they write in the medical journal Experimental Gerontology. Home-based resistance training can be done with exercises that simulate daily physical activities and can be adapted to each person's physical condition.

Earlier studies showed that "even minimally supervised home-based resistance training can be a safe, effective and low-cost exercise option to increase lower body muscle strength in older individuals with a variety of health conditions," the researchers say. The agency urges anyone with any medical condition discuss the exercises with their physician before starting. 

Hydroxychloroquine fails to protect medical workers

The malaria drug hydroxychloroquine failed to protect healthcare workers caring for COVID-19 patients from becoming infected themselves, according to results of a formal, placebo-controlled trial published on Saturday in Clinical Infectious Diseases.

The 1,483 participants worked in emergency departments, intensive care units, and other high-risk sites in the United States and the Canadian province of Manitoba. They were randomly assigned to receive hydroxychloroquine 400mg, once weekly or twice weekly, for 12 weeks, or a placebo.

Compared to the risk of infection in the placebo group, the risk was 28% lower with once-weekly hydroxychloroquine and 26% lower with twice-weekly dosing. But those differences were not deemed to be statistically significant, meaning they could have been due to chance rather than to the drug.

The University of Minnesota researchers point out that recruiting participants became difficult after potential adverse heart effects of the drug were publicized, and also that the hydroxychloroquine doses may have been too low. "Investigation into more frequent dosing may be warranted," they said.