When a clinical study to create a vaccination that lowers heart attack risks accidentally creates a novel deadly flu variant, a medical missionary is forced to team up with the virus’s creators to stop a potential global pandemic that could kill millions. The missionary nun and her spy companions are forced to rely on a brutal Russian biocontainment unit if they are to escape from the Caribbean island’s deranged dictator and find a cure to prevent a global disaster.

This is so interesting! You clearly have a clear understanding of the story you want to write, but less might be more. Cutting down some details about the virus itself could leave more room to talk about the other things. Also removing passive language raised the stakes and hook more people! An example using just what you’ve written:

When a clinical study accidentally creates a deadly flu variant, a medical missionary is forced to team up with the virus’ creators to stop a global pandemic. The missionary nun and her spy companions are forced to rely on a brutal Russian bio containment unit if they are to escape from the Caribbean island’s deranged dictator and find a cure to prevent a global disaster.