Ports around the US are rolling out vaccines for seafarers, extending a lifeline to thousands of mostly foreign workers who’ve spent the pandemic isolated aboard ships ensuring goods keep trading across a battered global economy.

From Boston to Houston and Los Angeles, and even in smaller trade gateways like Gulfport, Mississippi, local health officials and nonprofits are boarding container ships, tankers and other cargo carriers to administer Covid-19 shots or, when possible, shuttling crews to nearby pharmacies and clinics...