Cytomegalovirus, or CMV for short, belongs to the herpesvirus family, along with the herpes simplex, Epstein-Barr, and chickenpox virus. It causes a mononucleosis-like disease similar to EBV, mainly in teens and young adults (they don’t call it ‘the kissing disease’ for nothing!), and in children the primary infection may have no symptoms at all or mimic another viral infection. Like all herpesviruses, it stays in the body indefinitely, occasionally and asymptomatically entering the bloodstream and other bodily fluids. Transmission to another person is usually accomplished by sharing utensils, kissing, and rarely via blood products. In immunosuppressed people, CMV (either primary infection or reactivation) can cause very severe and life-threatening infections.
However, the most common form of damage caused by this virus happens when a woman is primarily infected with CMV in early pregnancy, or if the virus reactivates at that point (which is probably somewhat less risky). According to the CDC:
* Between 50% and 80% of adults in the United States are infected with CMV (cytomegalovirus) by 40 years of age
* CMV is the most common virus transmitted to a pregnant woman’s unborn child
* Approximately 1 in 150 children is born with congenital CMV infection
* Approximately 1 in 750 children is born with or develops permanent disabilities due to CMV
* Approximately 8,000 children each year suffer permanent disabilities caused by CMV
* Congenital CMV (meaning present at birth) is as common a cause of serious disability as Down syndrome, fetal alcohol syndrome, and neural tube defects.
Congenital CMV is the most common cause of congenital non-heritable deafness and cerebral palsy, and the second most common cause of mental retardation (after Down Syndrome) in the developing world.
Though many women have already had CMV by the time they reach reproductive age (here in Israel, more so than in the US), I managed to remain CMV negative and as far as I know, still am. When I was having babies, I had to keep on reminding the OB to test and retest me for CMV during pregnancy, just in case I’d acquired it (and let’s face it – in my line of work, I am at high risk of doing so). Nowadays, at least in the clinic I work in, we’ve made testing for CMV and toxoplasma (another microorganism which can cause severe birth defects) routine.
I’ve often wished there was a CMV vaccine available. After all, you need it for the same reasons as the rubella vaccine. Now, it seems I may one day get my wish:
In a manufacturer-supported phase II study of CMV glycoprotein B vaccine with MF59 adjuvant, investigators randomized 464 CMV-seronegative postpartum women to receive three doses of vaccine (at baseline, 1 month, and 6 months) or placebo within 1 year after delivery. Participants were followed for ≤42 months. CMV acquisition was determined with viral culture, polymerase chain reaction assay, or antibody testing, and women used diaries to report adverse events.
Overall, 8% of vaccine recipients and 14% of placebo recipients acquired CMV during follow-up (P=0.02); vaccine efficacy was 50%. Congenital CMV infection occurred in 1 of 81 infants (1%) born to all vaccine recipients and 3 of 97 infants (3%) born to all placebo recipients (P=0.41). The vaccine was moderately reactogenic: Incidence of myalgias, arthralgias, and chills was higher in the vaccine group than in the placebo group. After the third dose, 3% of vaccine recipients reported severe injection-site pain.
Comment: These results show that even a single-antigen CMV vaccine can provide substantial protection to postpartum women; moreover, such protection might translate into lower rates of congenital CMV infection. In general, this vaccine has lower efficacy than others already on the market — 50% versus at least 90% for most vaccines — and is moderately reactogenic, probably because of the MF59 adjuvant. However, these results raise hopes for development of a successful CMV vaccine.
The abstract of the study commented on is here.
And here’s the layperson’s audiovisual version, courtesy of the University of Alabama at Birmingham:
More great resources on congenital CMV: