Boosters are important and they strengthen the dog's immunity. Missing shots of booster is fine though but this means that the dog is having the less protection and repeating the dog's vaccine because you forgot what he took already is not harmful but expensive. That is why date of vaccinations is important. My [link=http://www.trainpetdog.com/Saint-Bernard/about-saint-bernard.html]saint bernard[/link] has complete vaccines and has no problem because my I have an organize schedule.