The following is a summary of some recent studies on Covid-19. They include research that warrants further study to corroborate the findings and that has yet to be certified by peer review.
Half of the Covid-19 patients discharged from a Chinese hospital in early 2020 still have at least one symptom two years later, a new study shows.
Overall, regardless of initial disease severity, the 2,469 Covid-19 survivors in the study had improvements in physical and mental health over time.
Nearly 90 per cent of those who were employed returned to their jobs within two years. But the survivors had a "remarkably" lower health status than the general population at two years, and their burden of symptoms from after-effects "remained fairly high," the researchers reported on Wednesday (May 11) in The Lancet Respiratory Diseases.
At two years, 55 per cent still had at least one Covid-19 after-effect, according to the report. Fatigue or muscle weakness were the most frequently reported symptoms during the study.
Patients who had required mechanical ventilation for critical illness still had high rates of lung impairments at two years.
"Our findings indicate that for a certain proportion of hospitalised Covid-19 survivors, while they may have cleared the initial infection, more than two years is needed to recover fully from Covid-19," the researchers said.
Patterns of inflammatory proteins in the blood of people with long Covid may someday help guide individualised treatment, new findings suggest.
Researchers studied 55 people with long Covid who had been only mildly ill with Covid-19 and found that roughly two-thirds had high levels of inflammatory proteins in their blood, with the ongoing inflammation most likely to be found in individuals with the highest burden of long Covid symptoms.
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"While earlier research has shown high levels of such proteins in long Covid patients, we provide the first evidence that more than half" have a specific signature, or pattern, while others do not, the researchers reported on Tuesday on bioRxiv ahead of peer review.
"At least two different patterns of inflammatory proteins were detected," said study leader Troy Torgerson of the Allen Institute for Immunology in Seattle.
The existence of these patterns suggests the immune system is being activated in specific ways that could be responsive to treatment with existing anti-inflammatory or immunosuppressive medicines, Torgerson said.
"Measurement of these proteins in blood could help to identify long Covid patients who may be good candidates for treatment studies using these drugs or possible future treatments."
Increased contact among vaccinated people can give the false impression that Covid-19 vaccines are not working, researchers warn.
Some studies have suggested that vaccinated individuals are becoming infected at higher rates than unvaccinated individuals, but these studies are likely to involve statistical errors, particularly if they did not account for different contact patterns among vaccinated vs unvaccinated people, said Korryn Bodner of St. Michael's Hospital, Unity Health Toronto.
Using computer models to simulate epidemics with a vaccine that protects against infection and transmission, her team identified conditions that could create "a perfect storm for observing negative vaccine effectiveness even when a vaccine was efficacious," Bodner said.
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Effective vaccines could appear ineffective when vaccinated people have more contact with each other than with unvaccinated people, when vaccine benefits become lower but are not absent (as has happened with new SARS-CoV-2 variants), or when effectiveness is measured while an epidemic is growing (such as when a new variant is emerging), according to a report posted on medRxiv ahead of peer review.
The simulations do not prove that this type of bias affected studies of vaccine effectiveness versus the Omicron variant.
They show, however, that "even if vaccines work, increased contact among vaccinated persons can lead to the appearance of the vaccine not working," Bodner said.
