David Brill
American researchers have scored “a home run” in the quest to prevent congenital cytomegalovirus (CMV) infections – a leading cause of birth defects in newborns.
In a recent phase II trial they found that a new vaccine was 50 percent effective at preventing CMV infection among women, after a minimum of 1 year follow-up.
Just 18 of 234 women who were vaccinated went on to develop CMV infection, compared to 31 of 230 women in the placebo group. [N Engl J Med 2009 Mar 19;360(12):1191-9]
Further trials are now needed to confirm whether immunizing mothers will actually translate to a reduction in congenital infections, said lead researcher Dr. Robert Pass.
With phase III trials also required it is likely to be at least 5 years before the vaccine is licensed, he said. It also remains unclear whether CMV immunity persists or would need boosters.
Successful CMV vaccines have so far proved elusive: none are currently licensed despite more than 30 years of research and a ‘top priority’ listing by the US Institute of Medicine in 2001.
“CMV is a very complex virus which has a long-standing relationship with its host,” said Pass, who is professor of pediatrics at the University of Alabama at Birmingham, US.
“When this trial was initiated most people did not think we would find any efficacy for prevention of maternal infection. So to find that the vaccine was actually able to prevent infection in women was essentially a home run.”
Around 0.7 percent of babies are born with a congenital CMV infection – 11 percent of whom are symptomatic at birth. Fetal damage typically occurs in cases where the infection is acquired during pregnancy: around 0.5 percent of such babies die and up to 20 percent have permanent disabilities. [N Engl J Med 2009 Mar 19;360(12):1250-2]
CMV is endemic in Singapore – the virus was present in 87 percent of antental women screened at KK Women’s and Children’s Hospital (KKH) from 1997 to 1998. [Singapore Med J 2000 Apr;41(4):151-5]
Dr. Lai Fon Min, a consultant and head of the antenatal risk assessment unit at KKH, said that there is an important need for CMV vaccines since there are limitations to both maternal and fetal screening, and no accepted therapy for congenital infections.
“If a highly effective vaccine for CMV is developed there may be justification in introducing it in Singapore as we have a high prevalence rate,” he said, but added that it “remains to be seen” whether routine vaccination would be cost effective.
The vaccine tested by Pass and colleagues comprises 0.02 mg of CMV envelope glycoprotein B, along with 13.25 mg of a squalene-in-water emulsion known as MF59. The rights are owned by Sanofi Pasteur.
The study was not designed to assess outcomes among newborns but the findings appear promising: just one of 81 babies born to vaccinated mothers had CMV, whereas three of 97 babies born to placebo-group mothers were infected.
The trial enrolled CMV-seronegative women who had given birth within the previous year. They were vaccinated at 0, 1 and 6 months, and tested quarterly for CMV infections over 42 months.
Injection-site reactions were more common in the vaccinated women but overall adverse event rates were not significantly different to placebo.
Pass added that vaccination could either be performed in pre-teen girls – potentially in combination with the human papillomavirus vaccine – or in very young children, since they are the main source of CMV infections for pregnant women.
Just 18 of 234 women who were vaccinated went on to develop CMV infection, compared to 31 of 230 women in the placebo group. [N Engl J Med 2009 Mar 19;360(12):1191-9]
Further trials are now needed to confirm whether immunizing mothers will actually translate to a reduction in congenital infections, said lead researcher Dr. Robert Pass.
With phase III trials also required it is likely to be at least 5 years before the vaccine is licensed, he said. It also remains unclear whether CMV immunity persists or would need boosters.
Successful CMV vaccines have so far proved elusive: none are currently licensed despite more than 30 years of research and a ‘top priority’ listing by the US Institute of Medicine in 2001.
“CMV is a very complex virus which has a long-standing relationship with its host,” said Pass, who is professor of pediatrics at the University of Alabama at Birmingham, US.
“When this trial was initiated most people did not think we would find any efficacy for prevention of maternal infection. So to find that the vaccine was actually able to prevent infection in women was essentially a home run.”
Around 0.7 percent of babies are born with a congenital CMV infection – 11 percent of whom are symptomatic at birth. Fetal damage typically occurs in cases where the infection is acquired during pregnancy: around 0.5 percent of such babies die and up to 20 percent have permanent disabilities. [N Engl J Med 2009 Mar 19;360(12):1250-2]
CMV is endemic in Singapore – the virus was present in 87 percent of antental women screened at KK Women’s and Children’s Hospital (KKH) from 1997 to 1998. [Singapore Med J 2000 Apr;41(4):151-5]
Dr. Lai Fon Min, a consultant and head of the antenatal risk assessment unit at KKH, said that there is an important need for CMV vaccines since there are limitations to both maternal and fetal screening, and no accepted therapy for congenital infections.
“If a highly effective vaccine for CMV is developed there may be justification in introducing it in Singapore as we have a high prevalence rate,” he said, but added that it “remains to be seen” whether routine vaccination would be cost effective.
The vaccine tested by Pass and colleagues comprises 0.02 mg of CMV envelope glycoprotein B, along with 13.25 mg of a squalene-in-water emulsion known as MF59. The rights are owned by Sanofi Pasteur.
The study was not designed to assess outcomes among newborns but the findings appear promising: just one of 81 babies born to vaccinated mothers had CMV, whereas three of 97 babies born to placebo-group mothers were infected.
The trial enrolled CMV-seronegative women who had given birth within the previous year. They were vaccinated at 0, 1 and 6 months, and tested quarterly for CMV infections over 42 months.
Injection-site reactions were more common in the vaccinated women but overall adverse event rates were not significantly different to placebo.
Pass added that vaccination could either be performed in pre-teen girls – potentially in combination with the human papillomavirus vaccine – or in very young children, since they are the main source of CMV infections for pregnant women.
1 comment:
Can you write an article about how prevelant and under-reported congenital CMV is? My daughter was born severely brain damaged because I didn't know the prevention methods to take. I'm trying to raise awarenes and would love to see more articles teaching prevention until a vaccine is approved. You can see my CMV work at www.authorlisasaunders.com
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