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Researchers working on effective CMV vaccine

Developing a vaccine against cytomegalovirus (CMV) is right at the top of researchers’ priority list. However, most people have never heard of the virus. CMV is common, with a third of children in the U.S. infected by the age of 5, and well over half of people are infected by the age of 40. A CMV vaccine is a priority because of the problems it poses for transplant recipients and the babies of women infected during pregnancy.

CMV spreads through contaminated body fluids such as saliva and urine. It is, therefore, not surprising that it spreads easily within child daycares. Most infections go unnoticed, but those with symptoms suffer sore throat, swollen lymph nodes and tiredness. Symptoms are usually mild, short-lived and rarely merit diagnostic testing. CMV remains dormant for life but still sheds in saliva and urine. Several CMV strains exist, and people can have repeat infections with different strains. 

There are more than 40,000 organ transplants in the U.S. each year. Many recipients are infected with CMV before transplantation or become infected after transplantation by the people around them. Due to shortages of organs, a recipient without CMV may become infected by an organ from a donor who carries the virus. Regardless of how a recipient became infected, their medications to prevent organ rejection interfere with the ability of their immune system to control CMV. The virus can grow unchecked damaging vital organs such as the liver, eyes, and heart. It can also lead to the rejection of the transplant.

Thankfully, medications and antibody treatments can usually control CMV, although it greatly complicates care. Other severely immunocompromised people, such as those with AIDS, can develop similar problems with CMV.

Pregnant women may pass CMV to their unborn child, which is most likely to occur if it is the mother's first CMV infection. It rarely arises from a previous infection or an infection with a new strain. CMV infects one out of every 200 newborns in the U.S. Most of these babies are fine, but one out of five will have long-term issues. Sometimes it is clear at birth that something is wrong. The baby may have a temporary purple rash that makes it appear like a "blueberry muffin" or a small head that is out of proportion to its body. The small head usually indicates the baby will have a lifelong intellectual disability. The baby may have seizures and problems with the liver, spleen, eyes, and lungs. Hearing problems are common, and babies appearing healthy at birth may develop hearing difficulties over time. Pregnant women are not usually tested for CMV. Medications and antibody treatments have not been demonstrated to prevent mothers from passing the virus to their babies. Still, they are often used to treat infection after birth.

Currently, the only CMV preventive measures we have are avoiding exposure and handwashing, which are nearly impossible for anyone around young children. Researchers have been working on effective CMV vaccines for decades. Hopefully, we will have an effective vaccine soon.

Megan Berman
Richard Rupp
Vaccine Smarts is written by Sealy Institute for Vaccine Sciences faculty members Drs. Megan Berman, an associate professor of internal medicine, and Richard Rupp, a professor of pediatrics at the University of Texas Medical Branch. For questions about vaccines, email