If viral infections like flu cause meningococcal carriage to be more common or cause people to carry higher numbers of meningococcal bacteria and so, probably, to be more infectious than others, then widespread use of flu vaccines may result in reductions in the circulation of meningococcus and so less disease. The way we use meningococcal vaccines might also be changed to focus efforts more efficiently on blocking transmission at critical times and places.
Decisions about whether or not to use vaccines depend increasingly on mathematical models. Essentially these are large sums that work out how much disease and how many deaths will be prevented and how much all of that is worth compared to the cost of buying and administering the vaccine. Often it is hard to get these sums right because it is not known exactly how well the vaccines will work. This is especially true about their ability to reduce disease by reducing circulation of the bacteria that cause disease in the population. The results of this study will help improve the information used in these kind of sums and so increase the confidence with which policy decisions about new vaccines can be made.