10 million doses of polio vaccine arrive in Khartoum
Almost 10 million doses of polio vaccine arrived in Khartoum last week. The vaccines will be used to immunise 8.6 million children under the age of five during the National Polio Campaign planned for October.
Vaccine-derived poliovirus type 2 (cVDPV2) was confirmed in Sudan on August 8. This strain of poliovirus is the result of low immunity and under-immunisation of communities, rather than a problem with the vaccine itself (more about this at the bottom of this article).
The vaccination campaign, the first to be held nationwide in response to the virus detection, is being led by the federal Ministry of Health, and supported by WHO and UNICEF. The aim is to boost immunity and protect vulnerable children against the virus. This year, thousands of children missed out on vaccinations due to the impact of the COVID-19 pandemic on health care systems and communities, worsening an existing immunity gap.
“UNICEF and its partners support local authorities to control the spread of polio”, said Abdallah Fadil, UNICEF Representative in Sudan. “As part of these efforts we have procured the 10 million doses of polio vaccine. The campaign will be accompanied by a social mobilisation campaign to encourage communities to get their children vaccinated.”
“We must protect children from the threat of polio, and the best way to do that is to increase the polio vaccination coverage and urge parents and communities to bring their children for vaccination to save them from polio, which can cause paralysis or even death. A little effort now can give children the best health care service that they need in their first years of life.”
“Vaccinating every child is the only way to stop this outbreak spreading further”, said Dr. Niema Saeed, WHO Representative in Sudan. “There is a multi-country outbreak in four out of the seven countries bordering Sudan. In addition to in-country efforts we started coordination with countries bordering Sudan to have holistic and comprehensive response.”
Last year, UNICEF provided Sudan with 7.1 million doses of oral polio vaccine (OPV) for routine vaccination activities, and 13.5 million doses of oral polio vaccine for a campaign aiming to reach 7.6 million children through multiple vaccination activities.
The polio vaccination campaign in Sudan is supported by the Global Polio Eradication Initiative (GPEI), an organisation dedicated to the eradication of polio. The GPEI is spearheaded by national governments, the World Health Organisation (WHO), Rotary International, the US Centers for Disease Control and Prevention (CDC) and UNICEF, and supported by key partners including the Bill & Melinda Gates Foundation and GAVI, the Vaccine Alliance.
Wild polio and vaccine-derived polio
Multiple strains of polio exist. There is a critical distinction between wild poliovirus, which is today only found in Afghanistan and Pakistan, and the vaccine-derived strain detected in Sudan.
Oral polio vaccine (OPV) contains an attenuated (weakened) vaccine-virus, activating an immune response in the body. When a child is immunised with OPV, the weakened vaccine-virus replicates in the intestine for a limited period, thereby developing immunity by building up antibodies. During this time, the vaccine-virus is also excreted. In areas of inadequate sanitation, this excreted vaccine-virus can spread in the immediate community (and this can also offer protection to other children through ‘passive’ immunisation), before eventually dying out.
On rare occasions, if a population is seriously under-immunised, an excreted vaccine-virus can continue to circulate for an extended period of time. The longer it is allowed to survive, the more genetic changes it undergoes. In very rare instances, the vaccine-virus can genetically change into a form that can paralyse – this is what is known as a circulating vaccine-derived poliovirus (cVDPV).
It takes a long time for a cVDPV to occur. Generally, the strain will have been allowed to circulate in an un- or under-immunised population for a period of at least 12 months. Circulating VDPVs occur when routine or supplementary immunisation activities are poorly conducted and a population is left susceptible to poliovirus, whether from vaccine-derived or wild poliovirus. Hence, the problem is not with the vaccine itself, but low vaccination coverage. If a population is fully immunised, they will be protected against both vaccine-derived and wild polioviruses.
13 million cases prevented
Since 2000, more than 10 billion doses of oral polio vaccine have been administered to nearly three billion children worldwide. As a result, more than 13 million cases of polio have been prevented, and the disease has been reduced by more than 99 per cent. During that time, 24 cVDPV outbreaks occurred in 21 countries, resulting in fewer than 760 VDPV cases. The small risk of cVDPVs pales in significance to the tremendous public health benefits associated with OPV.
Circulating VDPVs in the past have been rapidly stopped with two or three rounds of immunisation campaigns. The solution is the same for all polio outbreaks: immunise every child several times with the oral vaccine to stop polio transmission, regardless of the origin of the virus.
Until 2015, over 90 per cent of cVDPV cases were due to the type 2 component in oral polio vaccins. With the transmission of wild poliovirus type 2 already successfully interrupted since 1999, in April 2016 a switch was implemented from trivalent OPV to bivalent OPV in routine immunisation programmes. The removal of the type 2 component of OPV is associated with significant public health benefits, including a reduction of the risk of cases of cVDPV2.
More information about polio and polio vaccines can be found in this GPEI factsheet.
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