Clinical trials in Asia, Africa confirm safety, effectiveness of rotavirus vaccine

Two studies published online Thursday in the Lancet show that the rotavirus vaccine is safe and effective at preventing much of the gastrointestinal illness in developing countries, where rotavirus kills more than 400,000 children under age 5 annually, Reuters reports. Based on the findings in Asia and Africa, the studies' authors "urged the governments of developing nations to make the vaccines a priority," the news service writes.

Though rotavirus vaccines "are now part of the regular schedule for infants in the United States and other developed countries … [t]he two studies show they would also be effective in places without sure supplies of clean water or medical care, where diarrhea is one of the major killers of young children," Reuters continues (Fox, 8/5).

In 2009, the WHO recommended that oral rotavirus vaccines be incorporated into national childhood immunization programs, based partly on the preliminary data from these trials, according to an accompanying Lancet Comment (Nelson/Glass, 8/6).

For the study conducted in Asia, researchers performed a randomized controlled trial on more than 2,000 infants ages 4-12 weeks "in rural Matlab, Bangladesh; and an urban and semi-urban part of Vietnam," according to the study. The children "were randomly assigned to receive three oral doses of pentavalent rotavirus vaccine 2 mL or placebo at around 6 weeks, 10 weeks, and 14 weeks of age, in conjunction with routine infant vaccines including oral poliovirus vaccine," the authors of the study write (Zaman et al., 8/6).

"After two years, 38 vaccinated babies got severe rotavirus infections, compared to 71 babies that got placebo, making the vaccine 48 percent effective against severe disease," Reuters writes (8/5). Additionally, "[r]ates of serious adverse events were low in both the vaccine (2.5%) and placebo (2.0%) groups, with no serious adverse event considered linked to receipt of the intervention," according to a Lancet press release.

"With a WHO recommendation for rotavirus vaccines now in place, governments of developing countries in Africa and Asia are deciding how to prioritise introduction of rotavirus vaccine in their public health agendas," write the authors of the Asia rotavirus vaccine trial in the Lancet. "Our trial shows that a live oral rotavirus vaccine has the potential to halve the incidence of severe rotavirus gastroenteritis in developing populations in Asia," they add (8/6).

The efficacy study of the rotavirus vaccine in Africa involved infants ages 4-12 weeks, who were divided into groups receiving the oral vaccine or placebo at 6, 10 and 14 weeks of age. The trial involved over 5,400 infants, including those with HIV/AIDS, and was conducted in "in rural areas of Ghana and Kenya and an urban area of Mali," according to the study.

After two years, "[t]he researchers recorded 79 cases of severe [rotavirus gastroenteritis] RVG in the vaccine group, compared with 129 in the placebo group, giving a vaccine efficacy of 39%," the Lancet press release continues. "Rates of serious adverse events were again low in both the vaccine (1.5%) and placebo (1.7%) groups, with the most common reported event being gastroenteritis," the press release adds (8/5).

The "pentavalent rotavirus vaccine provided significant protection against severe rotavirus gastroenteritis in infants for nearly 2 years of follow-up," the authors of the study write, adding that "this protection was especially high through the first year of life (64.2% vaccine efficacy), when the disease burden, including mortality, is highest."

The authors continue, "In Africa, where young children are dying from diarrhoeal disease and prompt medical care is often out of reach, the need to prevent rotavirus is especially urgent. Introduction of rotavirus vaccines for African children, along with imminent introduction of pneumococcal and meningococcal conjugate vaccines in parts of Africa, could instigate a new era of reduction of childhood disease and mortality" (Armah et al., 8/6).

In the accompanying Lancet Comment, Anthony Nelson of the Chinese University of Hong Kong, and Roger Glass of the National Institutes of Health examine how the WHO's rotavirus "recommendation would allow the GAVI Alliance to accelerate introduction of the vaccine into the national immunisation programmes of the world's 72 lowest-income countries by subsidising vaccine purchase for a limited time at a price of US$0.10—0.30 per dose." Even with the reduced prices on the vaccine, they ask, "Will national decision makers in low-income countries now heed WHO's advice and introduce rotavirus vaccines?"

"Although the reduced price might entice some policy makers, many are concerned that without a guaranteed reduction in price in the future, their rotavirus immunisation programmes will become unsustainable when the subsidy ends," they explain. "The price of vaccines is expected to decrease when developing country manufacturers enter the market but, for now, rotavirus vaccine is only available from the two multinational manufacturers," according to Nelson and Glass (8/6).

VOA News features an interview with Glass about the study findings (Berman, 8/5).