The seafarers keeping the supply chain moving aren’t getting the vaccines they need

When the Covid vaccine became available in Smrutiranjan Nanda’s home state of Odisha, in India, he took it, getting the first shot in March, and the second in April. It was a relief. India was in the midst of a brutal wave of the virus fueled by the Delta variant, and he had lost his mother to Covid. He did not want to be infected.

But by the next month, his assessment had shifted. “I made a very big mistake,” Nanda said.

Nanda, 49, is a second officer on container ships with a career spanning...