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Vaccine Protects Newborns From Growing Pertussis Threat

By Daniel J. DeNoon
WebMD Health News

Reviewed by Louise Chang, MD

Oct. 24, 2012 -- Women should get a Tdap shot during every pregnancy to protect their infant from whooping cough, even if they have had Tdap shots before, new guidelines advise.

Today's recommendation comes from the CDC's Advisory Committee on Immunization Practices (ACIP), the panel that sets U.S. vaccination policy.

The new shot recommendation is meant to protect newborns from pertussis, better known as whooping cough.

Pertussis kills babies, particularly those under 2 months of age. So far this year, at least 16 U.S. infants have died of pertussis. But that's just "the tip of the iceberg," Baylor University pediatrician Carol Baker, MD, told the panel.

"I take care of babies who die of pertussis," said Baker, a former chair of the ACIP. "The official number of confirmed pertussis deaths is small. But these children die of apnea [inability to breathe], and a large number of SIDS [sudden infant death syndrome] deaths are probably pertussis."

Babies are vulnerable because they can't start vaccination against pertussis until they're 2 months old.

Previously, there was an effort to protect infants by making sure everyone around them was vaccinated. This "cocooning" strategy isn't working, the CDC's Jennifer L. Liang, DVM, told the ACIP. Too few people were getting their booster shots.

"Cocooning is an insufficient strategy to prevent pertussis in infants," Liang said.

Instead, the ACIP considered a new strategy: Vaccinate pregnant women. Protective anti-pertussis antibodies cross the placenta to the fetus, protecting newborns until they can make antibodies of their own. The optimal time to get the Tdap vaccine during pregnancy is between 27 and 36 weeks gestation.

Is Safety an Issue?

Is it safe? The Tdap vaccine has three components. It protects against tetanus and diphtheria as well as against pertussis. Healthy adults given repeat doses don't have a problem with getting two shots in two years, except that their arms tend to be sorer, and sore longer, than after the first shot.

The vaccine is known to be safe in pregnant women, and experts who testified before the ACIP suggested that the vaccine would be safe when repeat doses are given with each and every pregnancy.

The ACIP was troubled that there is no direct evidence this is true -- but the panel felt strongly that any small risk to a woman was outweighed by the larger risk of pertussis for her infant.

Pertussis cases are rising at an alarming rate. Last year saw the highest number of cases since the 1950s; there already have been more cases this year than last.

The pertussis surge comes as a new generation of vaccinated children reaches adolescence. In 1997, the ACIP recommended that a safer acellular pertussis vaccine could be used instead of the old whole-cell vaccine. Most of the developed world now uses the newer vaccine.

But now it appears that the new vaccine's protection wears off more quickly than the old one. Even though a high percentage of U.S. teens get a recommended booster shot of Tdap at age 11-12, there's been a surge of whooping cough in 12- and 13-year-olds.

Even so, the vast majority of deaths and hospitalizations are in infants. While the ACIP wrestles with the larger issue of how to deal with the growing problem of pertussis in teens and young adults, today's action is intended to protect this more vulnerable population.

The ACIP also voted to add the maternal Tdap vaccine to the vaccines included in the Vaccines for Children program. This means that nearly all public and private insurers will cover the cost of the shots.

SOURCE: Yale University, news release, Oct. 22, 2012