Human Cytomegalovirus & The Unborn Infant

The largest risk group and the most compelling reason for developing a Human cytomegalovirus (HCMV or CMV) vaccine is for the unborn infants of mothers who experience primary infection during pregnancy. A confirmed diagnosis of severe congenital infection is usually recommended for termination.

Vaccination of children against HCMV will be useful in protecting unborn children from birth defects by reducing the risks that mothers are exposed to infected children.

Q&A

How prevalent is HCMV in congenital cases?
Is a congenital CMV infection obvious to a mother during pregnancy?
Do we have any Queensland statistics on the prevalence of CMV?
What is the prognosis for infants infected via mother-child transmission during pregnancy?
How does mother first know her child may be affected?
So two of the largest risk groups are families with young children and people who work in child-care centres?
Can you have your children screened?
Is there an existing vaccine for HCMV?
What initiated the CRC-VT's interest in the HCMV project?
Can you get CMV infection from this new type of vaccine?
For more information about our HCMV Vaccine Development Project

Links to other informative sites

How prevalent is HCMV in congenital cases?

This is something that is very difficult to determine. Over the years, many children have been diagnosed with congenital defects but nobody has known the complicated reasons behind these abnormalities. Rubella was once a problem, but the immunisation program that was implemented in schools in 1971 has greatly reduced its incidence in the community. Now we know that altered mental development, progressive loss of hearing, vision impairment - all those things may be related to primary CMV infection during pregnancy. CMV now has a similar profile to what Rubella had 20 years ago.

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Is a congenital CMV infection obvious to a mother during pregnancy?

A pregnant woman may not show obvious symptoms of CMV infection because her immune system can control it, but it's too late to control the danger to her baby because it's already crossed the mother-child barrier via the placenta. Here it starts affecting development, particularly if it's in the first 8 weeks of gestation (period of organogenesis - organ development) - a critical stage. It may not be until routine scans are performed that developmental problems are visibly evident.

Do we have any Queensland statistics on the prevalence of CMV?

As CMV is not a notifiable disease and there is no treatment for congenital infections, Queensland Health does not have current statistics on its diagnosis. The latest figures state that 40 - 60% of the Australian population have encountered a HCMV infection by the time they reach childbearing years. Around 30% of young children have a CMV infection and may shed the virus for 3 years or more, therefore having potentially infectious bodily fluids. Of the 250,000 babies born in Australia each year, approximately 200 will have a CMV infection.

What is the prognosis for infants infected via mother-child transmission during pregnancy?

90% of the babies born with the infection appear normal (asymptomatic - no visible symptoms), 10% are visibly affected with CMV and may have the most severe form, with a high risk of progressive complications and even death. However, 10 - 15% of the 90% of asymptomatic (no symptoms) cases go on to develop various progressive deteriorations as well.

How does mother first know her child may be affected?

Normally during a CT scan, a first sign may be the size of the head - lower than normal measurements. This is a sign to ask what is wrong? Genetic defect? Is baby impaired with something else or some mutation? The mother will be asked to go for tests for CMV, rubella. At this stage, once a congenital infection has been diagnosed, there's nothing you can do.

So two of the largest risk groups are families with young children and people who work in child-care centres?

Yes.

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Can you have your child screened?

Yes, but it's not necessarily useful. The infection can be transferred at any time. So, a child may be clear today, yet infected tomorrow. When kids go to day-care etc they bring infections home. It's quite common for mothers to become infected by their child, so child-mother transmission is very common (as with other viral infections). If a mother is pregnant and has a child at day-care, she has to be very careful and take preventative measures against CMV. That's a large group of women and we know that 40 - 60% of the population are at risk of a primary infection.

Women must be made aware so they are not left asking, "Why wasn't I told about CMV?" when it's too late. The fact that we've treated rubella so successfully, means we are now seeing other types of viral infections that are seeming to be more prevalent.

Is there an existing vaccine for HCMV?

No. Attempts at attentuated (weakened) CMV vaccines have already failed. The CRC-VT strategy is not going in that direction.

What initiated the CRC-VT's interest in the HCMV project?

The CRC-VT held a workshop where we attempted to identify new targets suitable for CRC projects. At the same time, a report commissioned by the National Institutes of Health and published by the National Academy of Sciences (USA), entitled Vaccines for the 21st Century - A Tool for Decision Making, identified a HCMV vaccine as one of the seven most favourable vaccines to be developed in the next decade.

The CRC-VT looks for technology based projects that will enhance our existing IP and we were already working on a vaccine for Epstein-Barr virus (EBV) with much success. HCMV is a similar virus to EBV. Our technology was well refined to map CTL epitopes - a viable strategy for formulating a new vaccine, therefore the HCMV was an ideal target upon which the CRC-VT could overlay its EBV knowledge.

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Can you get CMV infection from this new type of vaccine?

No. The vaccine formulation that we propose is not based on the virus particles at all. It's a synthetic vaccine and therefore has no viral components.

For more information about our HCMV Vaccine Development Project:

Links to other informative sites:

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