Whooping cough, or pertussis, is a very contagious disease that is most serious for babies. People with whooping cough usually spread the disease by coughing or sneezing while in close contact with others. Parents, older siblings, or other caregivers can give whooping cough to babies without even knowing they have the disease. Vaccination against Pertussis remains the strongest prevention against this disease. Immunization during the last trimester of pregnancy, as well as current vaccination of the individuals who will be in contact with an infant, are vital health protection measures for infants during the time they are too young to receive vaccination.