Updated

Moms-to-be should get a booster tetanus, diphtheria and pertussis (Tdap) vaccine during each pregnancy to help protect their infants from whooping cough, according to a new vaccine schedule released today by the Centers for Disease Control and Prevention (CDC).

Babies don't get their first pertussis vaccine until two months of age - and even then, they aren't fully protected until after their third shot, at six months. In the interim, they are at especially high risk of getting very sick from the bacterial disease.

During a 2010 whooping cough outbreak in California, for example, more than 9,000 cases were reported and 10 infants died.

Vaccinating pregnant women serves the dual purpose of keeping moms from contracting whooping cough and passing it to their infants as well as allowing some immune cells to pass to babies through the placenta.

"It turns out that immunity wanes pretty quickly," said Dr. H. Cody Meissner, a pediatrician from the Tufts University School of Medicine in Boston who is on the CDC's immunization committee.

"Without boosting with each pregnancy, a mother's immunity will wane and she will have much less immunity to pass on to the baby," Meissner told Reuters Health.

Cocooning

Although not part of the new immunization schedule, experts recommend immunizing a new baby's father, siblings and other caretakers. That strategy is known as cocooning.

"It's a good time to make sure that everyone who will be caring for the child is also up to date on their vaccines," said Dr. Daniel McGee, a pediatrician with Helen DeVos Children's Hospital in Grand Rapids, Michigan, who wasn't involved in the new guidelines.

"You need to make sure if grandma and grandpa are coming to visit, they're protected as well," he told Reuters Health.

Along with the new guidelines for pregnant women, updates to the CDC's vaccination schedule include a routine Tdap shot for adults age 65 and older and a pneumococcal vaccine approved for adults with immune compromising conditions like kidney failure.

Some children who are ill, such as with sickle cell disease, should get meningococcal vaccines starting at two months of age, according to the schedule. Other kids don't have to start those shots until middle school.

The influenza vaccine is still recommended annually, but will now protect against four strains of flu rather than three, said Erin Kennedy, a medical epidemiologist at the CDC.

Parents should educate themselves as best they can on recommended vaccines, researchers said.

"It's quite complicated, and it does change all the time. But it's imperative for people to stay up to date and informed about which vaccines are available," Meissner said.

"There are 16 vaccine preventable diseases that children receive immunizations against in the first 18 years of life," he added. "If vaccination rates fall, we're going to see increases in some of these diseases."

Because the immunization program has focused on children, Kennedy said some adults don't know the schedule also calls for them to get a range of vaccinations based on their age, health or where they travel.

"Adults need to be aware of the fact that there are vaccines that are recommended throughout the lifespan," she told Reuters Health. "Right now coverage is low for all of these vaccines."

Updates to the CDC's vaccination schedule were published concurrently on Monday in Pediatrics and the Annals of Internal Medicine.