COVID-19 cases in the Americas increased by 12.7 percent last week from the prior week, the Pan American Health Organization (PAHO) said on May 4, as infections continued to rise in Central and North America.

Part of what is being discovered about the Omicron variant of Covid-19 is how fast it appears to infect people, a median of about three days, compared to four or five with other variants.

AstraZeneca Plc’s Covid-19 vaccine demonstrated 74 percent efficacy at preventing symptomatic disease, a figure that increased to 83.5 percent in people aged 65 and older, according to long-awaited results of the company’s U.S. clinical trial published on Sept. 29

Merck & Co. and partner Ridgeback Biotherapeutics said on Wednesday they had begun enrolling patients in a late-stage trial of their experimental drug molnupiravir for the prevention of Covid-19 infection.

AstraZeneca released primary analysis showing that the company’s AZD1222 vaccine demonstrated 76 percent efficacy against symptomatic Covid-19, 100 percent efficacy against severe or critical disease and hospitalizations, and 85 percent efficacy against symptomatic Covid-19 in people 65 years and older.

The first big real-world study of the Pfizer/BioNTech vaccine to be independently reviewed shows the shot is highly effective at preventing Covid-19, in a potentially landmark moment for countries desperate to end lockdowns and reopen economies.

Israel’s largest healthcare provider reported a 94% drop in symptomatic Covid-19 infections among 600,000 people who received two doses of Pfizer’s vaccine in the country’s biggest study to date.