To be granted a product license, a vaccine must present adequate quality, safety and efficacy. Studies on these criteria often utilize target species in a laboratory setting. Vaccines that had been proven effective during laboratory analysis may not present the same features when sold on a large scale, after encountering field conditions, and furthermore, can even produce complications. Measures are already in place to detect adverse reactions as reported by veterinarians to manufacturers, so that vaccines under suspicion of failing can be identified and investigated. The present review article describes the main problems, specifically adverse reactions and lack of efficacy, that have been encountered following release of vaccines for general use.(AU)