|Vaccines Spread Disease|
The observations have suggested that the vaccine's effectiveness falls off over time. To test that idea, the researchers studied the vaccine history of 2,698 children in 15 California counties during the 2010 outbreak, including 682 who developed whooping cough and 2,016 controls. Fifty-three cases (7.8 percent) and 19 controls (0.9 percent) had not received any whooping cough vaccine. Compared with controls, children with whooping cough had lower odds of having received all doses of DTaP. The corresponding vaccine effectiveness was 88.7 percent.
When children were categorized by time since finishing the series, children with pertussis were less likely than controls to have received their fifth dose within the previous 12 months with a vaccihe vaccine effectiveness of 98.1 percent. But after 60 months or longer, the vaccine effectiveness fell to 71.2 percent. The study adds to the "growing consensus" that the acellular vaccines work less well than the earlier whole-cell vaccines, according to Dr. Eugene Shapiro of Yale University School of Medicine.
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