In addition to protecting against polio by inducing antibodies that kill the virus, OPV activates other protective mechanisms, including an innate immune system, thus making people resistant to infections caused by other viruses and bacteria. For example, in large scale multicenter clinical trials conducted in the 1970s during outbreaks of seasonal influenza, OPV protected more people from influenza than most flu vaccines do. Furthermore, observational studies in many countries suggested that the hospitalization rate and the overall mortality among children immunized with OPV were consistently lower compared with unimmunized children, even in the absence of poliovirus in communities.
These are reputable authors, to say the least.
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