Moderna Inc. said on May 5 early human trial data shows that a third dose of either the company’s current Covid-19 shot or an experimental new vaccine candidate increases immunity against variants of Covid-19 first found in Brazil and South Africa.

A U.S. health advisory panel on April 14 is set to review six reported cases of rare blood clots in women who received Johnson & Johnson’s Covid-19 vaccine one day after federal regulators paused the use of the shot to assess the issue.

The U.S. National Institutes of Health said on April 7 it had begun a mid-stage study to determine the risk of allergic reactions to Covid-19 vaccines made by Moderna Inc. and Pfizer Inc.

The U.S. drug regulator gave Moderna Inc. clearance to speed up output of the company’s Covid-19 vaccine by letting it fill a single vial with up to 15 doses, with the United States banking on rapid immunization to stem the spread of the deadly virus.

The United States may not need AstraZeneca’s Covid-19 vaccine, even if it wins U.S. regulatory approval, Anthony Fauci, the nation’s top infectious disease doctor told Reuters on April 1.

A critical component of the immune system known as T cells that respond to fight infection from the original version of the novel coronavirus appear to also protect against three of the most concerning new virus variants, according to a U.S. laboratory study released on March 30.

U.S. college students vaccinated with Moderna Inc.’s COVID-19 vaccine will be part of a new study to test mRNA-1273’s effectiveness in curbing the spread of the virus, the COVID-19 Prevention Network said on March 26.

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.

AstraZeneca Plc is likely to come out with a new, modified statement about the company’s Covid-19 vaccine after a data and safety monitoring board expressed concern that the data in the drug manufacturer’s recent public statement were outdated, U.S. infectious disease expert Dr. Anthony Fauci said on March 24.

Dr. Anthony Fauci, the top U.S. infectious disease expert, said on March 14 he hopes former President Donald Trump will push his supporters to get the Covid-19 vaccine and emphasized that pandemic-related restrictions should not be lifted prematurely.