In Canada, (not the states but often affected by laws there) the first Meningicoccal vaccine was introduced in 1987. Before that, cases had fluctuated by year but, since the 20s, had never gone above 350.
In the five years following the introduction of the shot, yearly cases exceeded 350; in '89 there were over 800 recorded cases.
These vaccines only targetted one of the possible six strains ("B" I believe) and, over the next decade, the "C" strain became prevalent. I got the "B" shot in '87, but both my kids got the "C" shot instead (not in addition to).
While the vaccines do seem to reduce carriage of specific strains, they also seem to cause an increase in carriage (non-symptomatic infection) in the other strains, so much so that the reduction in one is more than offset by increases in the others.
The current schedule calls for a vaccine that covers the "ACYW" strains, not "B". Further, there is a strain called "X" that doesn't have any vaccine and just happens to be the one that increases the most in the presence of vaccines.
Speaking of 1989:
In Canada, (not the states but often affected by laws there) the first Meningicoccal vaccine was introduced in 1987. Before that, cases had fluctuated by year but, since the 20s, had never gone above 350.
In the five years following the introduction of the shot, yearly cases exceeded 350; in '89 there were over 800 recorded cases.
These vaccines only targetted one of the possible six strains ("B" I believe) and, over the next decade, the "C" strain became prevalent. I got the "B" shot in '87, but both my kids got the "C" shot instead (not in addition to).
While the vaccines do seem to reduce carriage of specific strains, they also seem to cause an increase in carriage (non-symptomatic infection) in the other strains, so much so that the reduction in one is more than offset by increases in the others.
The current schedule calls for a vaccine that covers the "ACYW" strains, not "B". Further, there is a strain called "X" that doesn't have any vaccine and just happens to be the one that increases the most in the presence of vaccines.