Whooping cough typically isn't dangerous in adults, but it can make babies very sick. Because there isn't a vaccine for newborns, some experts recommend "cocooning" - vaccinating everyone who lives with an infant - as a strategy for protection.

An alternative that's been proposed is vaccinating pregnant women only against whooping cough, which is also known as pertussis.

"Everyone agrees that there's more pertussis circulating and there is more infant pertussis and more deaths," said Dr. Janet Englund, an infectious diseases researcher from Seattle Children's Hospital.

"More people need to be vaccinated and no one is going to be against vaccinating and cocooning," she told Reuters Health. "The question is, is it sufficient?"

Englund, who wasn't involved in the new study, said cocooning works best if everyone in a baby's life - including grandparents, babysitters and daycare teachers - are vaccinated. But as it stands right now, she added, very few families in the United States with a new baby at home get booster shots against pertussis at all.

For the new study, researchers in the Netherlands surveyed and tested family members in 140 households for whooping cough between 2006 and 2009. Most of those households were picked because they had an infant with whooping cough, though in a few cases another family member had been diagnosed.

Michiel van Boven from the Center for Infectious Disease Control in Bilthoven and his colleagues found babies were most susceptible to whooping cough when their moms were infected.

They calculated, for example, that in a four-person household, infants had a 40-percent chance of getting whooping cough if their mother had it - compared to a 15- or 20-percent chance if their father or older sibling was infected.

That could be because moms had more close contact with their babies during pregnancy leave, which is offered by law only to mothers in the Netherlands.

Because older siblings were more likely to get whooping cough in the first place, however, the researchers found that vaccinating moms and siblings would be similarly effective at protecting infants - whereas vaccinating dads seemed to be less important, they reported in the journal Epidemiology.

According to the U.S. Centers for Disease Control and Prevention, there were close to 19,000 cases of whooping cough reported in the United States last year - but many cases aren't reported. Of the 13 reported whooping cough deaths, 11 victims were babies, in whom the infection can lead to pneumonia and other breathing problems.

The CDC recommends the pertussis vaccine as part of a combination shot given at ages two, four and six months, and twice more during early childhood.

The combination vaccine, known as DTaP, runs $20 to $25 per dose.

Preteens or teens can get another dose of the pertussis vaccine for additional protection, since immunity wears off over time.

Englund said that pregnant women and their partners who didn't get a booster shot as a teenager should get vaccinated before their baby is born because it takes a couple of weeks to build up antibodies against infection. Ideally, though, all adults who are planning to spend time around young children should be vaccinated.

"You can't just select who you want to immunize," she said. "For a vaccine to work the best, you have to immunize everyone."

SOURCE: bit.ly/RfKKJp Epidemiology, online September 26, 2012.

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