Despite a high-profile visit to China by a team of international experts in January, the world is no closer to knowing the origins of Covid-19, according to one of the authors of an open letter calling for a new investigation into the pandemic.

The U.S. Food and Drug Administration issued new guidance for vaccine makers as the regulatory agency is preparing for the possibility of needing to approve Covid-19 booster shots against variants of the SARS-CoV-2 virus.

Novavax announced a Memorandum of Understanding (MOU) with Gavi, the Vaccine Alliance, to provide 1.1 billion doses of the company’s Covid-19 vaccine candidate NVX-CoV2373 for the COVAX Facility.

China called on the United States on Feb. 10 to invite the World Health Organization to investigate origins of the Covid-19 outbreak there, as sparring over the pandemic continued after the WHO wrapped up its field work in the Chinese city of Wuhan.

The head of a World Health Organization-led team probing the origins of Covid-19 said bats remain a likely source and that transmission of the virus via frozen food is a possibility that warrants further investigation, but he ruled out a lab leak.

A member of the World Health Organization-led team visiting the central Chinese city of Wuhan said he was surprised by the complexity of getting to the origins of the Covid-19 pandemic and that years of research lay ahead.

Global coronavirus cases surpassed 100 million on Jan. 27, according to a Reuters tally, as countries around the world struggle with new virus variants and vaccine shortfalls.

China on Jan. 23 reported a slight increase in new cases of Covid-19 as the country marked the anniversary of the world’s first coronavirus lockdown, in the city of Wuhan where the disease emerged in late 2019.

The United States called on China to allow an expert team from the World Health Organization (WHO) to interview “care givers, former patients and lab workers” in the central city of Wuhan, and ensure its access to medical data and samples.

A roundup of scientific studies on the novel coronavirus and efforts to find treatments and vaccines includes research on Covid-19 patients who still have symptoms 6 months after falling ill.