More polio
cases now caused by vaccine than by wild virus
November 26, 2019
LONDON (AP) — Four African countries have reported new
cases of polio linked to the oral vaccine, as global health numbers show there
are now more children being paralyzed by viruses originating in vaccines than
in the wild.
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In a report late last week, the World Health Organization and
partners noted nine new polio cases caused by the vaccine in Nigeria, Congo,
Central African Republic and Angola. Seven countries elsewhere in Africa have
similar outbreaks and cases have been reported in Asia. Of the two countries
where polio remains endemic, Afghanistan and Pakistan, vaccine-linked cases
have been identified in Pakistan.
In rare cases, the live virus in oral polio vaccine
can mutate into a form capable of sparking new outbreaks. All the current
vaccine-derived polio cases have been sparked by a Type 2 virus contained in
the vaccine. Type 2 wild virus was eliminated years ago.
Polio is a highly infectious disease that spreads in
contaminated water or food and usually strikes children under 5. About one in
200 infections results in paralysis. Among those, a small percentage die when
their breathing muscles are crippled.
Donors last week pledged $2.6 billion to combat polio
as part of an eradication initiative that began in 1988 and hoped to wipe out
polio by 2000. Since then, numerous such deadlines have been missed.
To eradicate polio, more than 95% of a population
needs to be immunized. WHO and partners have long relied on oral polio vaccines
because they are cheap and can be easily administered, requiring only two drops
per dose. Western countries use a more expensive injectable polio vaccine that
contains an inactivated virus incapable of causing polio.
The Independent Monitoring Board, a group set up by
WHO to assess polio eradication, warned in a report this month that vaccine-derived polio virus is
“spreading uncontrolled in West Africa, bursting geographical boundaries and
raising fundamental questions and challenges for the whole eradication
process.”
The group said officials were already “failing badly”
to meet a recently approved polio goal of stopping all vaccine-derived
outbreaks within 120 days of detection. It described the initial attitude of
WHO and its partners to stopping such vaccine-linked polio cases as “relaxed”
and said “new thinking” on how to tackle the problem was needed.
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