Federal health agencies on Tuesday called for a pause in the use of Johnson & Johnson’s coronavirus shot as they examine a rare blood-clotting disorder that emerged in six recipients.

Every state, the District of Columbia and Puerto Rico halted their rollout of the Johnson & Johnson vaccine almost immediately. The same went for the U.S. military, federally run vaccination sites, and CVS, Walgreens, and other stores.

Today, science writer Carl Zimmer explains the decision-making process, how long the suspension might last and the impact it could have not only in the U.S. but around the world.

Guest: Carl Zimmer, a science writer and author of the “Matter” column for The New York Times.

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Background reading: 

• Injections of Johnson & Johnson’s coronavirus vaccine came to a sudden halt across the United States on Tuesday after federal health agencies called for a pause in the vaccine’s use.
• The pause could continue for a week to 10 days, after expert advisers to the Centers for Disease Control and Prevention determined on Wednesday that they needed more time to assess a possible link to a rare but serious blood-clotting disorder.
• What does the pause mean for people who have recently received the Johnson & Johnson shot and how common are blood clots? Here’s what you need to know.
• Safety worries about the AstraZeneca and Johnson & Johnson vaccines have jeopardized inoculation campaigns far beyond the United States. The actions of American and European officials have stoked doubts in poorer countries, where a history of colonialism and unethical medical practices have left a legacy of mistrust in vaccines.

For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.

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