Valacyclovir Cuts Rate of Fetal Cytomegalovirus Infection by 71%

Congenital cytomegalovirus (CMV) infection can result in brain, liver, spleen, lung, and growth problems and, more commonly, hearing loss in infants. To date, there are no treatments to prevent viral transmission, and the highest risk of fetal injury occurs following a maternal primary infection early in pregnancy.

In a late-breaking presentation at IDWeek 2019, investigators from Israel sought to evaluate the effect of the antiviral drug valacyclovir on the rate of vertical transmission of CMV. Pregnant women with serologic confirmation of primary CMV infection during the periconceptional period and first trimester were included in the randomized, double-blind, placebo-controlled trial.

Participants were randomly assigned to a treatment group of either 8 grams/day of valacyclovir initiated at the time of serological detection and continued until amniocentesis, or placebo. The primary end point—the rate of vertical CMV transmission—was determined by amniotic fluid CMV polymerase chain reaction, and secondary end points were evidence of symptomatic congenital CMV infection, either in utero or postnatally.

Of the 90 women included in the data analysis, 45 received valacyclovir and 45 comprised the control group. With 2 twin pregnancies in the group, a total of 92 amniocentesis results were available. Five (11.1%) amniocentesis were CMV-positive in the valacyclovir group, compared with 14 (29.8%) in the control group, equaling an odds ratio of 0.29 (95% confidence interval [CI]: 0.09-0.90) for vertical CMV transmission.

“Amongst patients infected during the first trimester, a positive amniocentesis for CMV was significantly (p = 0.02) less likely in the valacyclovir arm (2/19) compared [with] placebo (11/23),” investigators reported. “No significant differences (p = 0.91) in CMV-positive amniocentesis were observed between study arms amongst patients infected periconceptionally.”

Overall, valacyclovir was found to reduce the rate of fetal infection by 71%.

Keren Shahar-Nissan, MD, pediatric emergency medicine fellow at Schneider Children's Medical Center of Israel and presenting author of the study, detailed the impetus for the research, summarized the key findings, and explained next steps in an interview with Contagion® at IDWeek (see video).

“Valacyclovir at a dose of 8 grams/day is effective in reducing the rate of fetal CMV infection following early maternal primary infection during pregnancy,” the research team concluded.

The study, Valacyclovir to Prevent Vertical Transmission of Cytomegalovirus After Maternal Primary Infection During Pregnancy, was presented as a late breaking oral abstract on Saturday, October 5, 2019, at IDWeek in Washington, DC.