My friends puppy has had one of his jabs but is going on holiday and is wondering if he can put his puppy with another puppy that has had both it's jabs for a week ? Cheers

ok this could be a tricky one... can the pup go back to the breeder?  It should be ok with the other puppy but may face germs it's mother hasn't given it resistence to, there's a temptation that being with a pup who's had injections that the person will take both pups out because they have limited socialisation time, the pups could simply have such a great time that they wreck the house/deteriorate in their training, focus on each other... two pups together are very difficult.  It's a shame your friend has a pup and then is going on holiday... my advice would be to take it back to the breeder for the week.