KUALA LUMPUR, Sept 26 – The World Health Organization (WHO) has warned the Philippines of a high risk of polio further spreading after an outbreak was declared last Thursday.
Two cases were reported this month, both caused by vaccine-derived poliovirus type 2 (VDPV2) involving a three-year-old girl from Lanao del Sur in southern Philippines and a five-year-old boy from Laguna Province, about 100km southeast of Metro Manila. The highly contagious disease returned 19 years after the Philippines was declared polio-free in 2000.
Environmental samples taken from sewage in Manila and a waterway in Davao in August have also tested positive for VDPV2.
“Vaccine-derived polioviruses are rarely occurring forms of the poliovirus that have genetically changed from the attenuated (weakened) virus contained in oral polio vaccine,” WHO said in a statement.
“They only occur when the vaccine virus is allowed to pass from person to person for a long time, which can only happen in places with limited immunisation coverage and inadequate sanitation and hygiene.
“Over time, as it is passed between unimmunised people, it can regain the ability to cause disease,” WHO explained.
Despite assuring that the risk of international spread from the Philippines to be low, WHO said the outbreak could get worse domestically due to the low level of immunisation.
“However, the risk of further spread within the Philippines is high due to limited population immunity (coverage of bivalent oral polio vaccine (OPV) and inactivated polio vaccine (IPV) was at 66 per cent and 41 per cent respectively in 2018) and suboptimal AFP (acute flaccid paralysis) surveillance,” WHO said.
The Philippines Department of Health (DOH) continued to recommend that all children be vaccinated according to the routine immunisation schedule.
“Immunisation coverage in the Philippines for oral polio vaccines is 66 per cent, but needs to be at 95 per cent,” Rabindra Abeyasinghe, WHO Philippines representative, was quoted telling reporters yesterday, according to Reuters.
Just 40 per cent of children under five have received a polio vaccine by injection.
“If we do the vaccination the way we normally did, and that 30 per cent are not vaccinated, you are seeing another outbreak in another couple of years,” he said.
Furthermore, WHO also requests all travellers and residents in polio-affected areas to be fully vaccinated against polio.
The Southeast Asian nation is expected to introduce an immunisation programme that will initially target children in two areas of the southern region of Mindanao next month.
According to WHO, polio, which mainly affects children below five years of age, invades the nervous system and can cause total paralysis in hours. Among those paralysed, 5 to 10 per cent die when their breathing muscles become immobilised.
The virus is transmitted from person to person mainly through the faecal-oral route. The WHO Western Pacific region was certified polio-free in 2000.