I used to expect a Slashdot poster to have either properly read or at least fairly summarize the article posted. This is the third time in a month period in which the title/summary has been misleading. It is this type of practice that assists the viral spread of the misleading headline/summary which eventually becomes the whole story for less discerning news sources.
The Reuters headline itself is much more accurate "Whooping cough vaccine fades in pre-teens: study", based on the content of the article itself. The statistics seem to say (correctly) that an unvaccinated child is disproportionally more likely to be infected with whooping cough. The discovery was that the vaccine used on children did not appear to be as effective over time as the booster shot schedule expected. The length of time from the last booster shot is correlated to the an increased chance of infection, which was larger than expected in later years. The conclusion being this booster shot cycle should adjusted so booster shots occur more frequently.
What would be more interesting is to discover whether it was the loss of herd immunity due to unvaccinated children which led to the outbreak. Vaccines are known to often be only effect 95-99% of the time and often fade over time requiring booster shots. As herd immunity levels decrease the chance of propagation throughout a population every time individuals are in contact increases. It possible and even likely that it was this loss of herd immunity that exposed the larger than expected "fading" in strength of the vaccine's effects, which otherwise would have remained relatively unrealized and unimportant.