As part of a nationwide response to the threat posed by the more contagious Delta coronavirus variant, New York City will require Covid-19 vaccinations or weekly tests for workers at city-run hospitals and clinics.

The Delta variant of the coronavirus is the cause of more than 80 percent of new U.S. Covid-19 cases, but the authorized vaccines remain more than 90 percent effective in preventing hospitalizations and deaths, said top U.S. infectious disease expert Anthony Fauci during a U.S. Senate hearing on July 20.

Sinopharm’s Covid-19 vaccine elicited weaker antibody responses against the Delta variant, based on the first published study of its effect against the more contagious version.

Swiftly rising coronavirus cases across the United States and abroad fueled fears of a pandemic resurgence on July 19 and sent shockwaves through stock markets as the highly contagious Delta variant appeared to be taking hold.

U.S. Surgeon General Vivek Murthy stood by federal guidance that those fully vaccinated against Covid-19 no longer needed to wear masks, while blaming social media companies for fueling vaccine misinformation.

Facebook on July 17 defended itself against U.S. President Joe Biden’s assertion that the social media platform is “killing people” by allowing misinformation about coronavirus vaccines to proliferate, saying the facts tell a different story.

Los Angeles County will reimpose its mask mandate during the weekend of July 16 in the latest sign that public health officials are struggling with an alarming rise in coronavirus cases tied to the highly contagious Delta variant.

In a roundup of scientific studies on the novel coronavirus, new findings shed light on why chronic lung diseases that block the airways increase patients’ risks for severe Covid-19 and researchers say the blood disorder anemia should probably be added to the list of risk factors for poorer Covid-19 outcomes.

Although there have been discussions about using different Covid-19 vaccines in combination, World Health Organization (WHO) chief scientist Soumya Swaminathan warned against it, calling it a “dangerous trend.”

The United States is reviewing the need for a third Covid-19 booster shot among residents who have already been vaccinated but needs to see more data to know if additional shots could raise people’s risk of serious side effects, a U.S. health official said July 13.