Kenya has confirmed three cases of vaccine-derived poliovirus in Garissa.
Following the outbreak, the World Health Organisation and the US embassy in Nairobi have advised people travelling there to get vaccinated.
The infections were confirmed in two children who were already paralysed while the third one was asymptomatic.
Ministry of Health has already notified the WHO and the Polio Eradication Initiative, which tracks outbreaks around the world.
The ministry said it is testing more children in Garissa, and preparing for mass vaccinations in the region.
The Kenyan outbreak was confirmed to be circulating vaccine-derived poliovirus type 2 (cVDPV2), which is common around the world in under-vaccinated communities.
It is different from the wild poliovirus, which was lastly reported in Kenya in 2013.
Vaccine-derived viruses are common around the world and were also reported in Britain and the United States last year.
However, last week, the US Embassy in Nairobi still issued an advisory to its citizens regarding the outbreak in Kenya.
“As of July 11, 2023, Kenya recently confirmed a poliovirus outbreak in the northeastern part of the country. The US Embassy advises all US citizens to review their poliovirus vaccinations. Anyone vaccinated against polio in the United States receives an inactivated poliovirus vaccine (IPV) that protects against all types of polioviruses including the one reported from Kenya,” the embassy said.
The WHO also advised travellers to the affected area in Kenya to be fully vaccinated against polio. “Residents from infected areas should receive an additional dose of OPV or inactivated polio vaccine within four weeks to 12 months of travel,” the WHO added.
The two paralysed children were seen by health workers on May 26 and 27, 2023.
They are Somali refugees residing in Fafi subcounty. The community contact is from Hagadera refugee camp, associated with frequent population movement with neighbouring Somalia.
“Genetic sequencing confirms the isolated cVDPV2 are linked to cVDPV2 currently circulating in Banadir, Somalia. The cases and community contact are all from Hagadera refugee camp, associated with frequent population movement with neighbouring Somalia,” the Polio Eradication Initiative, which reported the outbreak, said.
Ministry of Health has not publicly spoken about the confirmed cases.
However, an official from the Division of Disease Surveillance said they have begun preparations for emergency vaccination, as per internationally-agreed outbreak response guidelines.
“Surveillance for additional acute flaccid paralysis cases is being further strengthened, and subnational immunity levels are being analysed to identify potential un- or under-immunised populations and/or areas,” PEI added.
According to the WHO, vaccine-derived poliovirus is a well-documented type of poliovirus that has mutated from the strain originally contained in the oral polio vaccine (OPV).
The OPV contains a live, weakened form of poliovirus. On rare occasions, when replicating in the gastrointestinal tract, OPV strains genetically change and may spread in communities that are not fully vaccinated against polio, especially in areas where there is poor hygiene, poor sanitation, or overcrowding.
Further changes occur as these viruses spread from person to person. The lower the population immunity, the longer this virus survives and the more genetic changes it undergoes. In very rare instances, the vaccine-derived virus can genetically change into a form that can paralyse—this is what is known as a vaccine-derived poliovirus.
“The detection of VDPV in at least two different sources and at least two months apart, that are genetically linked, showing evidence of transmission in the community, should be classified as ‘circulating’ vaccine-derived poliovirus type 2 (cVDPV2). cVDPV2 continues to affect different areas of the world,” the WHO said.
Kenya lastly reported an outbreak of vaccine-derived polio in December 2020 and January 2021.
Three cases were also refugee children from Somalia at the Dadaab refugee camp.
At that time, the WHO reprimanded Kenya for not declaring a national outbreak immediately as required by the International Health Regulations.
“The committee noted that Kenya and Tajikistan had not declared the new outbreaks as national emergency and requested the Global Polio Eradication Initiative to have discussions with these countries about the importance of making such a declaration, notwithstanding the reported vigorous country responses,” the WHO's IHR Committee for Polio said in a statement.
Kenya last reported the wild polio case in 2013 when an outbreak in Somalia led to an importation of 14 cases to the country.
The WHO certified Africa free of the wild polio virus on August 25, 2020.