When the Department of Health (DOH) confirmed last September that polio is back in the country after 19 years, members of the Filipino medical community shook their heads. How could we let this happen?
Some were quick to point out that it was the result of vaccine hesitancy after the Dengvaxia controversy in 2017. But it wasn’t as simple as that.
A November 2019 polio outbreak situation report from the UNICEF-WHO Philippines attributed the outbreak to persistently low routine immunization coverage, as well as poor sanitation and hygiene.
Polio is spread through fecal-oral transmission in contaminated food or water, or through direct contact with a person infected with polio.
“It was like a time bomb, waiting to explode,” said Dr. Gigi Bibera, pediatrician and member of the Pediatric Infectious Society of the Philippines (PIDSP).
Bibera said it took many years for the virus to mutate and cause an outbreak and, due to the country’s low immunization coverage, what happened in the Philippines was “an expected phenomenon”.
“The immunization coverage was already low, and after the Dengvaxia scare, it became even lower,” she added.
The DOH recently announced the first case of polio in Metro Manila, a 3-year-old boy from Quezon City, bringing the total number of confirmed polio cases in the country to 16 since September. Most of those who fell ill are from areas in Mindanao with very poor sanitation; they are all children who never received the polio vaccine.
Bibera explained that the virus seen in these cases was not the “wild virus”.
“The virus is in the environment, it’s attenuated (a weakened form of the virus), hindi naman s’ya ’yung wild virus. But when one child gets it, slowly it will revert back, mutate back and will replicate in the child’s gut which will then be excreted, and another child can get it and again this will mutate,” she said.
“That’s why it’s called ‘circulating vaccine derived polio virus’ or CVDPV because it’s circulating from one child to another until such time that the virus has already mutated into the live, not the attenuated form but the pathogenic (or disease causing) form already.
“If the child is not immunized, the child will get the circulating vaccine derived polio virus.”
This process took years, continued Bibera. “ ’Yung nagsi-circulate na ’yun, matagal ’yun, years, because we have been polio-free for many years.”
Unfortunately, immunization coverage became low and everyone became susceptible, “so that circulating virus became a disease that is now the CVDPV”.
Why do vulnerable children still need the oral polio vaccine?
There are two types of polio vaccine: the inactivated polio virus vaccine (IPV) given as an injection and the oral polio vaccine (OPV). Most Filipino private pediatricians just have the IPV, and it is assumed that their patients have already received it.
But the DOH is encouraging parents and caregivers of children under 5 years old to get the OPV, even if they have already gotten the IPV. The DOH recently launched a national immunization campaign called “Sabayang Patak Kontra Polio,” which gives the oral vaccine for free at public and private hospitals.
“An oral polio vaccine is needed to actually stop the transmission, while the injectable or inactivated polio vaccine gives you individual protection,” Bibera said.
“For example, while your kids are already complete with IPV but we now know there is a circulating oral polio virus in the environment, they can be exposed and may ingest the virus.
“When kids ingest the polio virus itself and they do not have the gut immunity that the oral polio virus gives, the polio virus can replicate in their stomach, in their gut.
“What will happen? They won’t get the disease because they are protected by the injection but they can excrete the virus and be the source, so the virus can now be transmitted to other children. You can be the source of the virus but not get the disease.”
There is no cure for polio
Dr. Maria Paz Corrales, assistant regional director of the DOH-NCR, said there is no treatment for polio and that immunization is the only way to prevent transmission.
“Polio disease has re-emerged in the Philippines after being declared polio-free in 2000. There were 142 environmental samples taken for testing for the presence of the polio virus. From these samples, 26 tested positive and of these, 25 are from NCR and 1 from Mindanao,” Corrales said.
“It is now because of this that we needed to conduct synchronized polio vaccination to achieve 95 percent community immunity.”
Corrales reported that the synchronized immunization was done August 19 to 31, 2019 (round 0), then round 1 from October 14 to 27 for the whole of NCR. Round 2 was done last December 25 to December 7 for the whole of NCR. For Mindanao, round 0 was on October 14-27 for Lanao del Sur, Davao City and Davao del Sur. Round 1 was done November 25 to December 7 for all Mindanao areas.
What is better, IPV or OPV?
“It’s not a question which is better. Ideally, you have to get both, because one, you want to protect yourself, and two, you want to protect the community at large,” Bibera said.
“We cannot eradicate polio if you don’t stop the transmission. It is your social responsibility to stop the transmission.”
More rounds of free polio vaccination will be done for all Mindanao areas and NCR from January to March 2020.
Corrales reiterated that the free polio vaccination is intended for children 5 years old and below, regardless of vaccination status.