This book discusses the benefits of complying with the national vaccination schedule in children under five years of age; where it is one of the priorities for the health sector in Mexico; taking into account the high morbidity and mortality rate due to immunopreventable diseases; where vaccination is one of the most effective actions for prevention.Vaccination is one of the most effective public health actions to prevent diseases and an obligation of the state. However, in Mexico there is no certainty about the coverage and timeliness with which vaccines are given to children during their first year of life (every year 2.3 million children are born in Mexico), these figures mean that up to 65.7% of children may not have their complete schedule or have received it late and, therefore, at risk of getting sick. In contrast, the Federal Health Secretariat in Mexico; admits that only 9.3% of children under one year of age are at risk for vaccine-preventable diseases.