The number of registered cases of whooping cough in the United States has increased significantly. Especially children under the age of 5 months are at the most risk, since they haven't been fully vaccinated against the disease. The number of cases was 19,798 in the '90s, an increase of 49% compared to the previous decennium!! The vaccin against whooping cough was developed in the '40s, before that time there were 160,000 cases of wooping cough every year, of which 5000 died a year. I wonder why this enormous increase, just because there are so many more people or maybe that the vaccination is becoming less effective due to a new strain?