New vaccine may reduce infection in unborn babies

An important cause of neurological impairment in infants—infection with cytomegalovirus while they are in the womb—may be curbed with the use of a new vaccine.

Most adults have been infected with cytomegalovirus or CMV, usually with negligible consequences. However, when women become infected with CMV for the first time while they are pregnant, there is a danger that their baby will also be infected. In some cases, this “congenital” CMV infection can lead to permanent defects such as hearing loss, vision loss, mental disability, lack of coordination, or seizures.

Now, a study in this week’s New England Journal of Medicine reports that a newly developed CMV vaccine reduces cases of CMV infection in women and has the potential to decrease congenital CMV infection.

“The development of a vaccine for the prevention of congenital CMV infection was listed as a top priority for the US by a committee of the Institute of Medicine in 2001,” Dr. Robert F. Pass, from the University of Alabama, Birmingham, and colleagues point out in the report.

Finding an effective CMV vaccine, however, has been a challenge. The first trials of a CMV vaccine began over three decades ago. In the present trial, the researchers tested a vaccine containing a protein found on the envelope of cytomegalovirus and an adjuvant to increase the immune response.

A total of 464 non-pregnant, CMV-negative women, between 14 and 40 years of age, were given three doses of the vaccine or an inactive “placebo” over a six-month period.

During follow-up, 18 CMV infections were seen in the vaccine group compared with 31 in the placebo group. Further analysis confirmed that women given the vaccine were significantly more likely to remain uninfected over a period of 42 months.

Ninety-seven women in the vaccine group and 118 in the placebo group became pregnant after vaccination. One congenital CMV infection occurred among 81 live births in the vaccine group, compared with 3 cases among 97 live births in the placebo group.

Two editorialists comment that although side effects were more common with the active vaccine, they were generally mild in nature, and further studies of the vaccine are therefore acceptable.

SOURCE: New England Journal of Medicine, March 19, 2009.