Pertussis vaccine losing its effectiveness?

(ABC) -- A vaccine against a common childhood ailment may be losing its effectiveness.

Pertussis, also known as whooping cough, is a highly contagious disease marked by violent coughing that makes it hard to breathe.

It most commonly affects infants and young children and can be fatal, especially in babies under the age of one.

A study in the journal “Pediatrics” notes that children given a newer version of the whooping cough vaccine during early childhood may experience an increased risk for whooping cough in later childhood. The proportion of reported pertussis cases among 7 to 10 year olds nearly doubled from 2007 to 2009 in a group that had received the new vaccine.

Experts say part of the reason is that immunity from the newer vaccine wanes in the years following the fifth and final dose. That means 7 to 10 year olds could be at an increased risk of whooping cough over time.