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COVID SCIENCE-Vaccine-linked heart condition tends to resolve quickly; Delta variant fuses cells to infect more efficiently

June 25 (Reuters) - 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.

Vaccine-associated myocarditis tends to resolve quickly

Cases of an inflammation of the heart muscle known as myocarditis have been reported after receiving COVID-19 shots, mostly in young men after the second dose of the mRNA vaccines. When myocarditis symptoms, such as chest pain and rapid or irregular heartbeats, do occur after vaccination, they usually resolve quickly, suggests a report of a small study published in the journal Circulation. Doctors tracked seven male patients, ages 19 to 39, who were hospitalized for myocarditis-like illness not long after receiving a COVID-19 vaccine manufactured by either Pfizer and BioNTech, Moderna - the two mRNA vaccines - or Johnson & Johnson. All recovered and left the hospital after two to four days of treatment. Study co-author Dr. Christopher deFilippi of the Inova Heart and Vascular Institute in Fairfax, Virginia, noted that in his health system, which represents about 2 million patients, myocarditis after COVID-19 vaccination has been a "rare event" and "fortunately so far associated with a benign outcome." The U.S. Centers for Disease Control and Prevention this week said reports of the heart condition occurred at a rate of 12.6 cases per million people who received either the Pfizer/BioNTech or Moderna vaccines, a higher rate than would be expected in the general population. However, deFilippi's team advised that given the dangers of COVID-19, even for younger adults, "the risk-benefit decision for vaccination remains highly favorable." (bit.ly/35NyLRv)

Delta variant’s spike fuses cells to infect them

Compared to the spike protein on earlier versions of the coronavirus, the spike on the worrisome Delta variant is better able to break into lung cells and fuse them together, researchers have discovered. "Spread by cell-to-cell fusion allows the virus to spread faster in infected people and partially hide from the immune system," said Markus Hoffman of Georg-August-University Göttingen in Germany, coauthor of a report posted on Wednesday on bioRxiv ahead of peer review. "For example, if a cell that is infected by the Delta variant is forced (by the spike protein) to fuse with a neighboring cell that is not yet infected, this allows the virus to enter the new cell much faster" than if the virus particles first needed to be released from a previously infected cell, he explained. By spreading via cell-to-cell fusion, the virus reduces its risk of encountering immune system cells that might attack and inactivate it, Hoffman added. These "skills" might make the Delta variant - first identified in India and now circulating widely in many countries - more transmissible, and the resulting illness more severe, the researchers said. The researchers also found that although the Delta variant can evade antibodies, it is not completely resistant. "It might be possible that the Delta variant can infect people who are vaccinated (especially if only one of two vaccine shots have been administered so far), but vaccination is highly effective in preventing severe disease," Hoffman said. (bit.ly/3A2bGIH)

Open tmsnrt.rs/3c7R3Bl in an external browser for a Reuters graphic on vaccines in development.

Reporting by Nancy Lapid; Editing by Bill Berkrot

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