Hyperimmune Globulin Fails to Prevent Congenital CMV Infection

Tara Haelle

July 28, 2021

Administering hyperimmune globulin to pregnant women who tested positive for cytomegalovirus (CMV) did not reduce CMV infections or deaths among their fetuses or newborns, according to a randomized controlled trial published online July 28 in The New England Journal of Medicine.

Up to 40,000 infants a year have congenital CMV infections, which can lead to stillbirth, neonatal death, deafness, and cognitive and motor delay. An estimated 35% to 40% of fetuses of women with a primary CMV infection will develop an infection, write Brenna Hughes, MD, an associate professor of ob/gyn and chief of the Division of Maternal Fetal Medicine at Duke University School of Medicine, Durham, North Carolina, and colleagues.

Previous trials and observational studies have shown mixed results with hyperimmune globulin for the prevention of congenital CMV infection.

"It was surprising to us that none of the outcomes in this trial were in the direction of potential benefit," Hughes told Medscape Medical News. "However, this is why it is important to do large trials in a diverse population."

The study cohort comprised 206,082 pregnant women who were screened for CMV infection before 23 weeks' gestation. Of those women, 712 (0.35%) tested positive for CMV. The researchers enrolled 399 women who had tested positive and randomly assigned them to receive either a monthly infusion of CMV hyperimmune globulin (100 mg/kg) or placebo until delivery. The researchers used a composite of CMV infection or, if no testing occurred, fetal/neonatal death as the primary endpoint.

The trial was stopped early for futility when data from 394 participants revealed that 22.7% of offspring in the hyperimmune globulin group and 19.4% of those in the placebo group had had a CMV infection or had died (relative risk [RR] = 1.17; P = .42).

When individual endpoints were examined, trends were detected in favor of the placebo, but they did not reach statistical significance. The incidence of death was higher in the hyperimmune globulin group (4.9%) than in the placebo group (2.6%). The rate of preterm birth was also higher in the intervention group (12.2%) than in the group that received placebo (8.3%). The incidence of birthweight below the fifth percentile was 10.3% in the intervention group and 5.4% in the placebo group.

One woman who received hyperimmune globulin experienced a severe allergic reaction to the first infusion. Additionally, more women in the hyperimmune globulin group experienced headaches and shaking chills during infusions than did those who received placebo. There were no differences in maternal outcomes between the groups. There were no thromboembolic or ischemic events in either group.

"These findings suggest CMV hyperimmune globulin should not be used for the prevention of congenital CMV in pregnant patients with primary CMV during pregnancy," Hughes told Medscape Medical News.

"A CMV vaccine is likely to be the most effective public health measure that we can offer, and that should be at the forefront of research investments," she said. "But some of the other medications that work against CMV should be tested on a large scale as well," she said. For example, a small trial in Israel showed that high-dose valacyclovir in early pregnancy decreased congenital CMV, and thus the drug merits study in a larger trial, she said.

Other experts agree that developing a vaccine should be the priority.

"The ultimate goal for preventing the brain damage and birth defects caused by congenital CMV infection is a vaccine that is as effective as the rubella vaccine has been for eliminating congenital rubella syndrome and that can be given well before pregnancy," said Sallie Permar, MD, PhD, chair of pediatrics at Weill Cornell Medicine and pediatrician-in-chief at New York–Presbyterian/Weill Cornell Medical Center and the New York–Presbyterian Komansky Children's Hospital, in New York City.

"While trials of vaccines are ongoing, there is a need to have a therapeutic option, especially for the high-risk setting of a mother acquiring the virus for the first time during pregnancy," Permar told Medscape Medical News.

Permar was not involved in this study but is involved in follow-up studies of this cohort and is conducting research on CMV maternal vaccines. She noted the need for safe, effective antiviral treatments and for research into newer immunoglobulin products, such as monoclonal antibodies.

Both Permar and Hughes highlighted the challenge of raising awareness about the danger of CMV infections during pregnancy.

"Pregnant women, and especially those who have or work with young children, who are frequently carriers of the infection, should be informed of this risk," Permar said. She hopes universal testing of newborns will be implemented and that it enable people to recognize the frequency and burden of these infections. She remains optimistic about a vaccine.

"After 60 years of research into a CMV vaccine, I believe we are currently in a 'golden age' of CMV vaccine development," she said. She noted that Moderna is about to launch a phase 3 mRNA vaccine trial for CMV. "Moreover, immune correlates of protection against CMV have been identified from previous partially effective vaccines, and animal models have improved for preclinical studies. Therefore, I believe we will have an effective and safe vaccine against this most common congenital infection in the coming years."

The research was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the National Center for Advancing Translational Sciences. Hughes has served on Merck's scientific advisory board. Various co-authors have received personal fees from Medela and nonfinancial support from Hologic; personal fees from Moderna and VBI vaccines, and grants from Novavax. Permar consults for Pfizer, Moderna, Merck, Sanofi, and Dynavax on their CMV vaccine programs, and she has a sponsored research program with Merck and Moderna on CMV vaccines.

N Engl J Med. Published online July 28, 2021. Abstract

Tara Haelle is a health/science journalist based in Dallas. She can be found at @tarahaelle.

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