vdb-config message - if using the module sratoolkit/2.10.7 for the first time, the command prefetch can show the following message:

$ prefetch -h
This sra toolkit installation has not been configured.
Before continuing, please run: vdb-config --interactive

If so, please enter the following:

vdb-config --restore-defaults

Then, you should be able to use the prefetch command as expected.