Are vaccines effective immediately?  Generally speaking, the immune system takes about 2 weeks to fully respond to a vaccine.

Is it OK for a pet to receive multiple vaccinations on the same day? Often this works out fine. In some cases though, the doctor may suggest separating the vaccines by a few weeks.

At times, some vaccines need to be boostered after 2 to 4 weeks. What happens if the pet does not come back to receive the booster vaccine? The pet will not have full immunity and the vaccine series will need to be restarted.