Rotavirus vaccine use likely contributed to a reduction in pediatric deaths in Mexico and a reduction in severe gastroenteritis in vaccinated African infants, according to two studies published today in The New England Journal of Medicine. However, a brief report in the same journal also cautions against use of rotavirus vaccines in children with severe combined immunodeficiency.
Researchers from the National Center for Child and Adolescent Health, Ministry of Health, Mexico City and the CDC said that a rotavirus vaccination program introduced in Mexico in February 2006 led to a marked reduction in deaths from diarrhea among young children.
The researchers compared annual deaths from diarrhea before and after the immunization program began. The researchers noted that for the three years before the vaccination program began, the median annual number of diarrhea-related deaths among children younger than 5 was 1,793, for a mortality rate of 18.1 deaths per 100,000. That number dropped to 1,118 deaths in 2008, which yielded a mortality rate of 11.8 per 100,000 children. The researchers said diarrhea-related mortality was 29% lower for children between the ages of 12 and 23 months, few of whom were age-eligible for vaccination, but mortality among unvaccinated children between the ages of 24 and 59 months did not change significantly.
The researchers noted that their study findings were limited in that it was not possible to attribute the reduction in deaths to vaccination, because precise vaccine coverage information is lacking and other changes, like improved hand hygiene, may have affected the rates.
In the second study, researchers in South Africa and Malawi enrolled 4,939 infants in clinical trials examining the efficacy of GlaxoSmithKline’s rotavirus vaccine, Rotarix.
Healthy babies were randomly assigned (1:1:1) to receive placebo followed by two or three doses of vaccine, or three doses of placebo, respectively, at 6, 10 and 14 weeks of age with routine childhood vaccines including oral poliovirus vaccine.
The researchers in that study noted rotavirus-related gastroenteritis occurred in 4.9% of the placebo group and in 1.9% of the pooled vaccine group, yielding a statistically significant vaccine efficacy of 61.2%. The researchers said efficacy against all-cause severe gastroenteritis was 30.2%.
In a brief report accompanying the two journal articles, researchers from Baylor College of Medicine noted that it is important to remember that the rotavirus vaccines can actually cause the disease in infants born with severe combined immunodeficiency.
In the report, experts examined three cases in which infants developed rotavirus disease after receiving the live attenuated rotavirus vaccine.
“All three infants (in the study) were vaccinated before they were diagnosed with severe combined immunodeficiency,” Paula Hertel, MD, assistant professor of pediatrics-gastroenterology at BCM and Texas Children’s Hospital, and study researcher said in a press release. “If the children could have been caught in a screening test done within days of birth, they may not have received the vaccine.”
While current routine newborn screening does test for many diseases, severe combined immune deficiency is not one of them, the researchers in the brief report noted.
Usually, experts recommend that children with severe combined immune deficiency not receive live vaccines. However, this vaccine must be given before most children are diagnosed with the immune disorder. The American College of Medical Genetics recently recommended that severe combined immunodeficiency be included as a part of the newborn screen.
Scientists analyzed the viral genetic material in stool specimens from the three children. This enabled them to determine that the rotavirus was of vaccine origin. This study led to a change in the vaccine exclusions listed on the vaccine manufacturer’s label to include a history of severe combined immunodeficiency.
The children did not successfully fight the infection until they underwent bone marrow transplantation or enzyme replacement therapy that gave them a functioning immune system, researchers noted.
The vaccine is very important for healthy infants, and in the United States, rotavirus cases decreased by 50% after the first season of vaccinations against the illness, said Hertel.
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