Chicago Mpox Cases Spark Fears Of a Summer Resurgence

US health officials are investigating a cluster of new mpox cases in Chicago, more than half of which are in people who were previously vaccinated against the virus.

“No vaccine is 100% effective, and infections after vaccination are possible,” the US Centers for Disease Control and Prevention said in a statement Wednesday.

The CDC said it’s unclear how long the mpox shot — called Jynneos — protects against infection, but that it is currently conducting studies to find out. The agency is also looking at specimen samples to see if the virus has mutated.

The situation has sparked worries that ...