If your dog misses a vaccination or treatment, it may be at risk of contracting a preventable illness. Depending on the type of vaccination or treatment, they may not be able to receive it at a later date, or the effectiveness of the vaccine could be decreased. Also, if your dog is exposed to a disease before the missed vaccination or treatment, it may be more susceptible to catching it. If you think your dog has missed a vaccination or treatment, it's important to contact your veterinarian as soon as possible to discuss potential risks and next steps.