When Three Shots Are Not Enough

People with compromised immune systems are getting unapproved fourth or fifth Covid-19 shots, despite uncertainty about their safety or effectiveness.

If asked to show her vaccine card, Stacey Ricks can choose from three.

Ms. Ricks, 49, a kidney transplant recipient who takes immune suppressing medication, didn’t develop antibodies after her first two Moderna shots.

In June, without disclosing she already had received the Moderna shots, she got a dose of the Johnson & Johnson vaccine before federal health officials had approved anyone for a third shot.