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Whooping cough, or pertussis, the very contagious, sometimes fatal respiratory disease is back—with a vengeance.

This chart, published by the CDC, shows the increase in reported cases of whooping cough in the U.S. since 1990:

Centers for Disease Control

Another one puts this rise into context:

Centers for Disease Control

It's the largest spike we've seen since the 1960s. Now, researchers from the Santa Fe Institute think they know why whooping cough is back. According to their research, the vaccines we use to protect ourselves from pertussis are good at blocking symptoms, but bad at stoping transmission of the disease. A statement explains that the acellular vaccines used to immunize from pertussis today—a less abrasive version of the ones we used in the 1950s—may have "contributed to" or "even exacerbated" the recent outbreak. Researcher Ben Althouse said, "There could be millions of people out there with just a minor cough or no cough spreading this potentially fatal disease without knowing it."

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The CDC recommends getting five installments of whooping cough vaccine, from two months until four years at the youngest. That means young children are the most vulnerable to catching the disease, and the CDC recommends that infants be only surrounded by those who have been fully vaccinated. But, as researchers point out, if the vaccine doesn't stop transmission, this method of protecting infants won't work. According to Althouse, "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."

In their conclusion, the authors note that "if our results hold, public health authorities may be facing a situation similar to that of polio, where vaccinated individuals can still transmit infection… In light of current evidence and our results, we cannot dismiss the potential far-reaching epidemiological consequences of asymptomatic transmission of B. pertussis and an ineffective B. pertussis vaccine."

Save us, science.

Danielle Wiener-Bronner is a news reporter.