Two doses of Pfizer or AstraZeneca’s Covid-19 vaccine are nearly as effective against the highly transmissible Delta coronavirus variant as they are against the previously dominant Alpha variant, a study published on July 21 showed.

Europe’s drug regulator started a real-time review of the Covid-19 vaccine developed by French drugmaker Sanofi and Britain’s GlaxoSmithKline, the fifth shot currently under such a review as of July 20.

Scientists are working on a benchmark for Covid-19 vaccine efficacy that would allow drugmakers to conduct smaller, speedier human trials to get them to market and address a huge global vaccine shortage.

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.

Executives from Pfizer met with government health officials to discuss Pfizer and BioNTech’s contention that booster shots for their COVID-19 vaccine will be necessary. 

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.

The U.S. Food and Drug Administration is planning a new warning for Johnson & Johnson’s Covid-19 vaccine over a rare but serious side effect, Guillain-Barré syndrome (GBS).

Health agencies and vaccine and immunology experts have pushed back against Pfizer and BioNTech’s assertions that a Covid-19 booster shot is necessary.

A potential Covid-19 vaccine developed by a subsidiary of China’s Livzon Pharmaceutical Group Inc. appeared safe and able to elicit antibodies in healthy adults in a mid-stage clinical trial, Chinese researchers said.

Pfizer and partner BioNTech plan to ask U.S. and European regulators within weeks to authorize a booster dose of the companies’ Covid-19 vaccine, based on evidence of greater risk of infection six months after inoculation and the spread of the highly contagious Delta variant.