NEW YORK (Reuters Health) - Pregnant women in their third trimester can safely receive the whooping cough vaccine to prevent infections in newborns, a recent study from the UK suggests.

Whooping cough, or pertussis, is a highly contagious disease. Its symptoms are initially mild but it can lead to serious and fatal complications, particularly for children under three months old.

Recent increases in whooping cough infections, some resulting in deaths of newborns, prompted the UK to develop a new vaccine program in 2012. The program offered combined vaccines against diphtheria, pertussis and polio to over 700,000 women in the third trimester of pregnancy.

"The benefit of maternal immunization is that the mother's protective antibodies are passed on to the baby before it is born, giving it the best protection it needs before they are old enough to be vaccinated themselves," Philip Bryan told Reuters Health in an email.

He worked on the study at the Medicines and Healthcare Products Regulatory Agency (MHRA) in London.

The U.S. Centers for Disease Control and Prevention (CDC) recommends that pregnant women are vaccinated against whooping cough, but the World Health Organization stated in a 2010 paper that there is not sufficient evidence to recommend the vaccine to pregnant women.

The MHRA sought to add to this body of evidence and ensure the UK vaccine program was safe. Bryan said the new study "is the largest review to date of the safety of whooping cough (pertussis) vaccination in pregnancy."

The researchers analyzed data on 20,074 pregnant women who were vaccinated against whooping cough beginning in late 2012.

Compared to country-wide estimates, there was no increased risk of stillbirth among vaccinated women. Their pregnancies resulted in five stillbirths in the two weeks following vaccination, while the existing data would predict about seven stillbirths in the same time frame. The pattern held true later in pregnancy as well.

Bryan and his colleagues also compared the vaccinated women to a group of similar but unvaccinated pregnant women from the previous two years.

That analysis suggested there was no increase in other pregnancy risks after vaccination either, including death of the mother or baby, pre-eclampsia, miscarriage, C-section delivery or low birth weight. In addition, the vaccine had no effect on the length of pregnancy, according to findings published in The BMJ.

In the U.S., the CDC recommends infants get vaccinated against pertussis initially at ages two, four and six months as part of a combined vaccine that also protects against diphtheria and tetanus called DTaP.

There is a significant advantage to administering the pertussis vaccine to pregnant women in addition to vaccinating infants, according to Dr. Eugene Shapiro, from Yale University in New Haven, Connecticut. He wrote an editorial published with the new study.

"With the current schedule, the three doses are not complete until six months," a time during which children are particularly vulnerable to the infection, Shapiro told Reuters Health.

In addition, he said the maternal vaccine "protects the mother so she doesn't become ill and transmit to the infant."

The pertussis vaccine has several known side effects, including redness and swelling at the vaccine site and fatigue and fever. But both children and adults generally tolerate it well, the researchers note.

"Sadly, we are still seeing deaths in newborns whose mothers did not receive the vaccine for whatever reason," Bryan said. "If worries over vaccine safety is a factor in some women not having the vaccine, then the results from our large study should give that extra bit of reassurance that the vaccine is safe in pregnancy, as well as very beneficial."

According to Bryan, the UK vaccine program has been a success. He noted that the vaccine's use has been steadily increasing in the UK and that it "has been highly effective at preventing disease and deaths in young babies."

SOURCE: http://bit.ly/1wbJBWB and http://bit.ly/1ldYcMb The BMJ, online July 11, 2014.