The Associated Press (AP) has reported that polio is spreading in Nigeria, with at least seven deadly outbreaks attributed to a strain of the virus that mutated from live-virus vaccines. According to AP reporter Maria Cheng, the World Health Organization (WHO) has warned that the vaccine-spread virus could spread beyond Africa.
The situation is complicated by the fact that vaccines have been the subject of deep distrust by some Africans. In 2003, Nigerian leaders suspended all vaccination efforts because they believed vaccines to be part of a conspiracy by the West to make Africans sterile or give them HIV. Injected vaccines, which are used in the West, are made of dead viruses that can’t cause infection, but vaccines used in developing countries are made from live, weakened viruses that carry a real, but extremely small risk of causing the disease, and an even smaller risk of mutating into a new strain. The oral vaccine is used in developing countries because it is not only far easier to store and administer, but because children who have taken the oral vaccine can pass the weakened virus into their local water supply through urine or feces. When unvaccinated children then play in or drink that water, they can pick up the weakened virus along with some protection from the disease. Unfortunately, in populations where the overall vaccination rate is lower than 95 percent, the virus very rarely incubates in an unvaccinated child and mutates into a new, full-strength strain.
According to WHO, in areas where the vaccination rate is near 100 percent, mutant-virus outbreaks are almost nonexistent. In Nigeria’s northern regions, approximately 15 percent of children go unvaccinated.
Polio cases from the vaccine-based virus have more than doubled in the past year. Sixty-eight children were paralyzed by the vaccine-based virus in 2008; to date in 2009, 124 children have been paralyzed, out of approximately 42 million children vaccinated this year. Cheng reported that for every child who contracts the virus, hundreds of others are asymptomatic carriers.
“Nigeria is almost a case study in what happens when you don’t follow the recommendations,” said virologist Olen Kew, PhD, of the U.S. Centers for Disease Control and Prevention (CDC).
Bruce Aylward, MD, who heads the WHO polio department, called the issue “very disturbing.” WHO officials had hoped to eradicate polio epidemics in India and Africa by the end of 2009. Aylward said that the situation in Nigeria did not mean that eradication was out of reach. “We still have a shot,” he was quoted as saying. “We’re throwing everything at it, including the kitchen sink.”