Progress toward Development of a Vaccine against Congenital Cytomegalovirus Infection

A vaccine against congenital human cytomegalovirus (CMV) infection is a major public health priority. Congenital CMV causes substantial long-term morbidity, particularly sensorineural hearing loss (SNHL), in newborns, and the public health impact of this infection on maternal and child health is underrecognized. Although progress toward development of a vaccine has been limited by an incomplete understanding of the correlates of protective immunity for the fetus, knowledge about some of the key components of the maternal immune response necessary for preventing transplacental transmission is accumulating. Moreover, although there have been concerns raised about observations indicating that maternal seropositivity does not fully prevent recurrent maternal CMV infections during pregnancy, it is becoming increasing clear that preconception immunity does confer some measure of protection against both CMV transmission and CMV disease (if transmission occurs) in the newborn infant. Although the immunity to CMV conferred by both infection and vaccination is imperfect, there are encouraging data emerging from clinical trials demonstrating the immunogenicity and potential efficacy of candidate CMV vaccines. In the face of the knowledge that between 20,000 and 30,000 infants are born with congenital CMV in the United States every year, there is an urgent and compelling need to accelerate the pace of vaccine trials. In this minireview, we summarize the status of CMV vaccines in clinical trials and provide a perspective on what would be required for a CMV immunization program to become incorporated into clinical practice.