According to statistics released by the World Health Organisation (WHO) this week, Nigeria, Democratic Republic of Congo, Central African Republic, and Angola have recorded nine new cases of polio caused by the live virus in oral polio vaccines.
This is likely the result of the viruses present in the vaccine mutating into an infectious form, reported The Scientist.
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In addition to this, other countries in Africa and Asia have also reported such vaccine-derived infections, which have the potential to spark new outbreaks. One of these, reported by FIT, was in Philippines last month, which is the country’s first cases of the disease in more than 25 years.
This development is especially worrying because as of now, there are more children affected by polio because of such vaccine-derived infections than those by wild type viruses.
The global total of vaccine-derived infections is 157 for the year, while the wild-type virus has affected 107 people this year.
The root of this problem has been traced back specifically to oral polio drops.
While injectable solutions of anti-polio vaccines use inactivated virus, the oral variety contains live, attenuated virus.
The latter is however, most commonly administered in third-world countries (where cases of vaccine-derived polio are concentrated) as they are cheap to produce and easy to administer.
However, the risk is that the attenuated live virus can mutate and become pathogenic.
Fortunately, once successfully vaccinated, one is protected even from vaccine-derived polio.
(Written with inputs from The Scientist.)
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