The head of the World Health Organization called Wednesday for a moratorium on administering booster shots of COVID-19 vaccines as a way to help ensure that doses are available in countries where few people have received their first shots.

New York City, Microsoft, Tyson Foods and the U.S. auto industry joined a cascading number of state and local governments and major employers Tuesday that are taking a hard line against both the surging delta variant and the holdouts who have yet to get vaccinated.

San Francisco will provide an extra dose of the COVID-19 vaccine for people who got the single-shot Johnson & Johnson variety but public health officials aren't calling it a booster, authorities said Tuesday.

Many of the companies that are requiring shots have mostly office workers who are already largely vaccinated and are reluctant to work alongside those who aren't.