While the pertussis infection can be mild in adults (often it is quite severe though), if a baby who hasn't received a full course of vaccinations is infected, whooping cough can be extremely serious. Mayo Clinic News reporter has more on how to recognize and treat this potentially deadly disease:
Infant girl with whooping cough -- Mother holding infant girl in Intensive Care Unit. The baby has pertussis (whooping cough) and is coughing severely. Warning: the video is hard to watch.
Everyone should receive the indicated vaccines to prevent potentially deadly diseases such as pertussis.