A booster dose of the Covid-19 vaccine developed by Pfizer Inc. and German partner BioNTech SE restored efficacy to 95.6 percent against the virus, including the Delta variant, data released by the companies from a large study showed on Oct. 21.

Scientists at the U.S. Food and Drug Administration said on Oct. 12 that Moderna Inc. had not met all of the regulatory agency’s criteria to support use of booster doses of the company’s Covid-19 vaccine, possibly because the efficacy of the shot’s first two doses has remained strong.

The effectiveness of the Pfizer Inc./BioNTech SE vaccine in preventing infection by the coronavirus dropped to 47 percent from 88 percent six months after the second dose, according to data published on Oct. 4 that U.S. health agencies considered when deciding on the need for booster shots.

Sage Therapeutics and Biogen announced positive and consistent results from their ongoing clinical trials on the efficacy and safety of zuranolone in treating major depressive disorder (MDD) and postpartum depression (PPD).

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

A potential vaccine from China’s Clover Biopharmaceuticals was 67 percent effective against Covid-19 of any degree of severity and 79 percent against the highly infectious Delta variant in a large trial, the company said on Sept. 22.

Initial results from a vaccine trial reported Sept. 20 showed that Pfizer and BioNTech’s Covid-19 vaccine might be safe for use in children under 12 years old. 

A British public health study found that protection from either of the two most commonly used Covid-19 vaccines against the prevalent Delta variant of the coronavirus weakens within three months.

The Covid-19 vaccines available in the United States are still highly effective at preventing hospitalization but their effectiveness against new infections has decreased as the Delta variant spread, according to new studies published on Aug. 18 in Morbidity and Mortality Weekly Report. A different study suggests children’s noses may be better than adults’ at defending against infection because of “pre-activated” immunity against the coronavirus.

Moderna Inc. said on Aug. 5 the company’s Covid-19 vaccine was about 93% effective through six months after the second dose, showing hardly any change from the 94% efficacy reported in the original clinical trial.