Researcher Rosalyn Singleton and her colleagues in the Centers for Disease Control and Prevention office in Anchorage found that invasive pneumococcal disease decreased 67 percent in Alaska Native children under age 2, and 61 percent in non-Native children of the same age between 2001 and 2003.
But evolving strains of bacteria not covered by the PCV7 vaccine cancelled those gains by 2006.
"The rapid success of PCV7 in Alaska has led to the near elimination of PCV7-serotype disease and the elimination of a health disparity for types covered by the vaccine," the authors wrote. "However, for Alaska Native children, there now exists a substantially elevated risk for IPD from serotypes not contained in PCV7.
In the first 3 years after introduction of routine vaccination with heptavalent pneumococcal conjugate vaccine, overall invasive pneumococcal disease decreased 67% in Alaska Native children younger than 2 years (from 403.2 per 100,000 in 1995-2000 to 134.3 per 100,000 per year in 2001-2003.....). However, between 2001-2003 and 2004-2006, there was an 82% increase in invasive disease in Alaska Native children younger than 2 years to 244.6/100,000... Since 2004, the invasive pneumococcal disease rate caused by nonvaccine serotypes has increased 140% compared with the prevaccine period.
Getting rid of the vaccine-targeted pneumococci evidently made life better for their non-vaccine-targeted relatives. That evolutionary medicine idea is looking better all the time.