When a vaccine that guards against the most common causes of pneumococcal disease comes to the market, it's simultaneously creating fresh opportunities for strains not covered in the shot, scientists have found.
In a new study, Dutch scientists have concluded that children vaccinated with Prevnar 7 were more likely than unvaccinated children to develop the 19A strain of pneumococcal disease. These results should serve as a warning that new strains of bacteria that cause pneumonia and meningitis are constantly threatening to break through the defensive perimeters created by immunization.
"It seems as though eradicating the seven types that are targeted by the vaccine makes room for new types," says Lieke Sanders of Utrecht's University Medical Center, who conducted the study. "Overall the net benefit is still good and there is a substantial decrease in the amount of disease, but new types are coming up and one of the most prominent types is 19A."
The study also supports use of Pfizer's new Prevnar 13 vaccine, which does guard against 19A. GlaxoSmithKline's Synflorix protects against 10 strains, including 19A. While Prevnar 7 cut the pneumococcal infection rate among children 5 and under by 99 percent, serotype 19A became the leading cause of infection in the infant and toddler crowd.
The bottom line: "It is a constantly moving target," says Sanders.