Vaccine stocks have tumbled since Robert F. Kennedy Jr.'s appointment to health secretary, with Moderna tumbling 8% to extend its plunge to nearly 31% since Trump's win.

London’s FTSE 100 struggled to maintain gains from earlier in the day and closed 7.58 points lower, or 0.09%, at 8,063.61.

Vaccine stocks slid late Thursday as reports stated noted anti-vaccine politician Robert Kennedy Jr. will serve as the next ...