I don't know how old your pup is, but pups go thru a number of fear periods as they mature. It is possible that the time of the Lepto vaccination & a fear period coincidentally happened at the same time & had nothing to do with each other. I posted an article below that may be of some interest regarding fear periods.
Lepto is one of the vaccinations that causes some of the worse reactions in dogs. It is also one that, in IMO, is the most worthless to give. The vaccine only covers 2-3 of the 7-8 strains of lepto that are around to infect your dog. So to me to give a vaccine that doesn't even cover the strains that are out there is useless to inject my dog with.
I give a parvo & distemper 2x & that's all. Rabies at a year. Many here do this & others choose to do no vaccines. It has to be an individual choice after your own research. Vets make a ton of $$$$s off of vaccines & many are more interested in their 'bottom line' then they are their patients. Again, JMO & experience.
The Critical Fear Periods in Puppies
By: Nancy Frensley, CPDT, CAP1
Berkeley-East Bay Humane Society Training Manager
The Critical Fear Periods in Puppies:
Seven to Nine Weeks
Four to Six Months
Approximately Eight to Nine Months
Approximately Twelve Months
Approximately Fourteen to Eighteen Months
During these periods, puppies may show fear of items, situations or people with whom they formerly felt safe. They may start barking at people entering a house or become fearful and startle at benign items like trash cans, drainpipes or even yard gnomes. They may crouch, shake and try to run away, submissively urinate or tell the scary thing/person to go away by showing an aggressive display (which could include piloerection, snarling, lunging or other unruly behavior.
You must be patient during these periods and keep to the familiar. These are not good times to introduce your puppy to new situations or people. Be very careful to avoid doling out punishment or reprimands. It’s vitally important that you understand that your dog is afraid and that you add to the fear when you reprimand or punish. This, in turn, can set the dog up for future aggression problems.
During these periods, introduce your puppy slowly to the situation, with good tasting treats, so that he or she does not experience fear. Control situations so that you can prevent a fearful response and show your puppy that you enjoy the situation. Use food treats and happy talk to lure your puppy up to scary objects. Teach the targeting exercise (touch your hand with his nose) and work on getting your puppy to “touch the goblin”.
When people visit your home during these periods, put your puppy in another room until visitors are settled in, then bring your puppy out on leash and praise for any show of confidence. Even have visitors toss good treats toward your puppy without approaching him or her.
MY DOGS...MY RULES