There are two types of vaccines available against polio virus: the inactivated (Salk, IPV) and the oral/attenuated (Sabin, OPV). Live vaccines are highly effective in inducing protective immunity against certain infections, also favoring the cessation of their epidemic spread. There are three wild serotypes of the polio virus, however currently two of them, serotype 2 and 3, are considered eradicated so that the only one that still circulates in endemic countries is serotype 1. One of the problems of OPV, which cannot occur with IPV, is its possible reversion to the wild form, circulating as vaccinal poliovirus (cOPV) and its transmission to unvaccinated people, giving rise to paralytic processes associated with the vaccine. To avoid this phenomenon, new oral polio vaccines (nOPV-c1) with greater safety and less reversion have been developed by modifying and introducing a series of genetic modifications in the RNA of the virus. Different studies have shown that children who received OPV2-c1 presented a higher degree of attenuation and thermostability and a highly significant decrease in the ability to affect the nervous system and develop severe neurovirulence and possible post-vaccination polio. These studies establish the pathogenic and molecular bases in the most vulnerable child population that allowed the use of this new genetically attenuated vaccine in population vaccination campaigns.
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