Can a child under 5 years get the whooping cough even though he received his shots as scheduled?

Whooping cough. The pertussis vaccine is only ~ 80-85% effective. That is why it is so important that all children be completely immunized. The greater the # of immunized children around each individual greatly decreases the chance of an exposure of an immunized child and hence illness in that child. This is called "herd immunity"., .