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New research has shown genetic resistance to rotavirus as the main cause behind low vaccine efficiency in developing countries.

Rotavirus is known to cause acute diarrheal illness and is directly responsible for nearly one-fifth of all child deaths in developing countries. Improving hygiene, and vaccination has not greatly improved infection rates and deaths. Vaccination only provides limited immunity. According to the study's author, in many African countries, the protection offered by two WHO recommended vaccines, Rotarix and RotaTeq, is as low as 50 percent.

"Today, vaccination is considered the most important method for reducing mortality. Unfortunately, several studies have shown that the two available living vaccines, Rotarix and RotaTeq, which are recommended by bodies including the World Health Organization, are not sufficiently effective in developing countries," a press release said.

The study's author Johan Nordgren from Linkoping University found four in 10 children in Burkina Faso genetically resistant to virus strains used in the vaccines. Nordgren attributes resistance to the absent expression of a sugar molecule in the intestine.

"Children who can not express a particular sugar molecule in the small intestine, called the Lewis molecule, do not become infected by the rotavirus types found in existing vaccines. This Lewis molecule is probably needed as a receptor for the rotavirus to be able to enter and infect the host cell in the intestine. This means that these children do not get the desired immunological protection from the vaccine," the author says.

"The occurrence of these Lewis-negative children is small in Europe and North America, but up to ten times higher in many African countries," the author said while adding the study could prompt evaluation of vaccines used, and lead to review of vaccine composition for making vaccines which are more suitable to populations that are genetically resistant to the vaccine virus infections required to promote immunity.

The findings will be published in the journal Clinical Infectious Diseases.