Literatus: The OPV question

Zosimo T. Literatus

THE last case of wild poliovirus was recorded in the Philippines in 1993, according to the World Health Organization (WHO). Thus, the country was also declared polio-free since 2000.

However, after only a quarter of a century (26 years) of being polio-free, the Philippines became infected with polio once again, and in an outbreak proportion. The Department of Health confirmed last month our first recent case of polio infection in a three-year-old girl in Lanao Del Sur. Moreover, sewage samples in Manila and Davao also confirmed the presence of poliomyelitis virus. It is just a matter of time when this virus spreads through the country, as it can be air-borne.

This is unfortunate because WHO has certified the global eradication of the “wild poliovirus type 2” in 2015. How this happened is a matter of Philippine history, which is outside the concern of this article.

Nevertheless, two factors appeared to converge in analyzing the present outbreak.

First, WHO noted that from the sewage samples taken from Manila, Davao and Surigao Del Sur, the current outbreak did not come from the wild poliomyelitis virus but from vaccine-derived poliovirus (also type 2). In short, this current polio outbreak came from polio vaccines and not from the wild type, which had been eradicated globally four years ago.

Second, as indicated above, failure of science appears to be involved. The oral polio vaccine (OPV), according to WHO, contains weakened (attenuated) samples of the poliomyelitis virus. These weakened forms activate the immune response of the children’s body.

However, what has not been anticipated is the capability of these weakened polioviruses to replicate in the intestine as children develop poliovirus immunity. These weakened viruses are excreted. Thus, for children not living in sanitized environments or not practicing proper hygiene, their feces can contaminate the environment. The presence of these polioviruses in the sewage confirms this situation. Eventually, these weakened polioviruses strengthen to become infections once again.

Now, a question must be asked: is continued use of the OPV safe? Evidently, its continued use will maintain the vicious circle through the mediation of poor environmental conditions, such as lack of sanitation in some communities and non-practice of hygienic behaviors.

Adding to the complexity is that at least 99 percent of children under age five have to be vaccinated yet, according to WHO. Moreover, which vaccine is safe to use?