A dangerous variant of the polio virus, which in some cases is able to break down vaccine protection, has been identified in the Congo, researchers report in the PNAS weekly.
The virus was detected in 2010 in Congo. It turns out that it can also develop in those people who have been vaccinated against the disease, say scientists from Germany and Gabon, who conducted research on the virus together.
The polio epidemic that broke out in Congo in 2010 was a particularly serious one. 445 people were found to be infected, mostly young adults. Of these, 209 people died. According to the researchers, such a high death rate was worrying.
Moreover, many of these people have been vaccinated before. Interviews with them confirmed that they remembered the vaccine taken in three doses.
Scientists isolated the virus for careful study. The pathogen has a mutation that changes its form at a key site. The result is that the antibodies produced by the vaccine are poor at blocking the mutant virus, describes Jan Felix Drexler, who led the virus research at the Institute of Virology at Bonn University Hospital.
In order to check how successfully the virus infects the immune system, researchers downloaded, among others blood samples from 34 medical students at the University of Bonn. They were all childhood immunized against polio.
As it turned out, their antibodies had no problem fighting the normal virus. However, in the case of the mutant, the immune response was much weaker.
“We estimated that one in five of our students in Bonn could be infected with the new virus, and perhaps even one in three” – sums up the research leader Prof. Christian Drosten.
The polio virus causes Heine-Medina disease. The World Health Organization is running an extensive polio vaccination campaign. In 2004, it announced that Europe was virus-free.
The goal is to eradicate polio completely, as has been achieved with smallpox. In 1980, it was announced that the world had been freed from the smallpox virus. Both viruses are similar in that they only pass from person to person. Animals are not the source from which the virus could spread to humans every now and then, causing epidemics.
Scientists warn that if such a changed virus were to find an unvaccinated population, the situation could be extremely dangerous. Current vaccines, used quickly and consistently, are now helpful. The Congo epidemic was brought to a halt by a massive vaccination program and improved hygiene. (PAP)