So this may come as a surprise, but in fact, polio cases have been on the rise globally since 2016, and this resurgent outbreak is related to the use of vaccines.

In 1955, the inactivated polio vaccines (IVP) were developed; and in 1962, the oral poliovirus vaccines (OPV) were invented.

Primarily through global distribution of polio vaccines (especially in developing countries) in conjunction with education and prevention campaigns, GPEI hoped to eradicate polio completely.

Mainstream media and public health agencies worldwide have unanimously and loudly praised the GEPI  and give all the credit of polio eradication to the vaccines and GEPI.  However, realistically speaking, the circulation of poliovirus in the world also has its own patterns, with peaks and declines with or without people’s intervention.  As a matter of fact, global polio cases entered a sharp decline phase from the late 1950s before the inactivated polio vaccine was widely distributed and before the oral polio vaccine was even invented.

And this time, the poliovirus strains that caused the outbreak were related to the vaccines.

Since the oral poliovirus vaccines (OPV) were produced with attenuated poliovirus strains, the viruses were not dead in the vaccine.

And OPV-2, a newer version of OPV with only type 2, was also produced separately to be used in poliovirus type 2 endemic areas.

After using the OPV with types 1 and 3 (bivalent OPV vaccine), the outbreak of cVDPV-2-related polio cases increased significantly from 2016.  This appears to suggest that the cVDPV-2 has been circulating at low levels before the switch was made in 2016.  So, the switch actually took away the pressure against cVDPV-2 and gave it more chances to cause small scale outbreaks in many regions of the world.

And now, the overall polio virus cases worldwide are back to the level of 20 years ago, even though more continents and countries are declared “Polio-free” ironically.

In addition, OPV can stimulate mucosal immunity in the intestines better than the inactivated vaccine.  Therefore, it has always been assumed that OPV can reduce the poliovirus transmission more effectively than inactivated vaccines, although no related tests have been done for any of the newer versions of the OPV.

In fact, if the inactivated polio vaccines (IPVs) were used instead of the OPVs, then there wouldn’t be this problem of generating circulating VDPVs.

It is well established that the wild type poliovirus has high mutation errors during its replication cycle, however, it is not known clearly whether the attenuated virus strains in the original OPV had a mutation rate as high as the wild type virus.

They made many modifications to the type 2 poliovirus genome, including mutations within the 5′-untranslated region (UTR), the RNA-dependent RNA polymerases, and other important regions.

Based on the public health emergency of international concern generated by ongoing endemic wild poliovirus transmission and cVDPV type 2 outbreaks, the WHO authorized nOPV2 for use under the Emergency Use Listing (EUL) pathway in November 2020, allowing for its first use for outbreak response in March 2021.

On the one hand, people want to wipe polio out from the face of the earth, yet on the other hand, the vaccines are “spreading” the viruses all over the world.  The VDPVs are still polio viruses, even though they are not wild type polioviruses.  Delta or Omicron variants are still SARS-CoV-2 viruses, even though they are not the wild type Wuhan strain?

Are we fooling ourselves by declaring some regions or countries as polio-free, simply based on not detecting wild type poliovirus, while we clearly know that VDPVs are still circulating, and even spreading faster due to the large OPV campaigns in many developing countries.

As mentioned earlier, the global polio epidemic was already on the decline before the vaccines were rolled out.