A scientist who has pored over public accounts of early Covid-19 cases in China reported on Thursday that an influential World Health Organization inquiry had most likely gotten the early chronology of the pandemic wrong. The new analysis suggests that the first known patient sickened with the coronavirus was a vendor in a large Wuhan animal market, not an accountant who lived many miles from it.

The report, published on Thursday in the prestigious journal Science, will revive, though certainly not settle, the debate over whether the pandemic started with a spillover from wildlife sold at the market, a leak from a Wuhan virology lab or some other way. The search for the origins of the greatest public health catastrophe in a century has fueled geopolitical battles, with few new facts emerging in recent months to resolve the question.

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Novavax, a Maryland-based company that received $1.75 billion from the United States government to develop a protein-based Covid-19 vaccine, announced Monday it had won emergency authorization for its vaccine in Indonesia.

After months of production delays, this is the first authorization for Novavax and its manufacturing partner, the Serum Institute of India. They have also applied for clearance in India and the Philippines, and Novavax has applied on its own to other countries, including Britain and Canada.

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The National Institutes of Health said on Wednesday that a nonprofit group under fire from some congressional Republicans for its research collaborations in China had failed to promptly report findings from studies on how well bat coronaviruses grow in mice.

In a letter to Representative James Comer, Republican of Kentucky, the N.I.H. said that the group, EcoHealth Alliance, had five days to submit all unpublished data from work conducted under a multiyear grant it was given in 2014 for the research. The organization’s grant was canceled in 2020 under President Donald J. Trump’s administration during his feud with China over the origins of the coronavirus.

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The Food and Drug Administration seems likely to allow Americans to switch vaccines when choosing a Covid-19 booster shot. That authorization, which could come this week, is the latest development in a long-running debate over whether a mix-and-match strategy helps protect people from the coronavirus.

Here are answers to some common questions about mixing and matching booster shots.

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When an advisory panel to federal regulators endorsed boosters for Johnson & Johnson’s one-dose Covid-19 vaccine on Friday, the scientists on the committee discussed a question many people are asking: Is it a good idea to mix and match vaccines?

The question came up after the panel heard a presentation about a study showing that the mix-and-match approach gives patients who received the Johnson & Johnson vaccine a stronger antibody response.

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