Building on that result, Althouse and Scarpino used whopping cough case counts from the CDC, genomic data on the pertussis bacteria, and a detailed epidemiological model of whooping cough transmission to conclude that acellular vaccines may well have contributed to—even exacerbated—the recent pertussis outbreak by allowing infected individuals without symptoms to unknowingly spread pertussis multiple times in their lifetimes.
"There could be millions of people out there with just a minor cough or no cough spreading this potentially fatal disease without knowing it," said Althouse. "The public health community should act now to better assess the true burden of pertussis infection."
What's worse, their model shows that if the disease can be spread through vaccinated, asymptomatic individuals essentially undetected, the level of vaccination needed to protect those that are unvaccinated (so-called 'herd immunity') is over 99 percent, impractically high at a time when anti-vaccine campaigns are turning people away from vaccination.
Their results also suggest that a practice called cocooning, where mothers, fathers, and siblings are vaccinated to protect newborns, isn't effective. "It just doesn't work, because even if you get the acellular vaccine you can still become infected and can still transmit. So that baby is not protected," Althouse says.