SEATTLE (AP) — U.S. researchers are opening tests of an experimental coronavirus vaccine with four healthy volunteers in Seattle.

Researchers at Kaiser Permanente Washington Research Institute gave each a shot in the arm, part of an early safety study that will track how 45 people fare.

The shots were developed by the National Institutes of Health in record time after the new virus exploded from China.

Several research teams worldwide are hunting a vaccine even as the pandemic grows. Monday's milestone is just the first step.

Experts say it will be at least a year before any vaccine is ready for widespread use.

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