It is a piece of worrisome news that the US has now joined a list of 30+ countries including the UK, Israel, Egypt, Yemen, and around two dozen in Africa where the circulation of the poliovirus has been identified, and a case of paralytic polio was reported from Rockland County in New York in July. Although polio vaccines have contained the virus globally, reporting of its spread in New York has alarmed US public health agencies. Unfortunately, since poliovirus is very good at finding unvaccinated individuals, the reports of a very low childhood polio vaccination rate in some New York communities are highly concerning.
There are two types of vaccines available against polio, one given as a shot in the arm or leg, and one given as a liquid orally. While many countries still use oral vaccines, the shot is the only one given in the US after 2000. Although both vaccines provide protection against wild poliovirus and vaccine-derived poliovirus, the viruses used in the oral vaccines can still spread when defecated in the stool despite being too weakened to cause serious disease. The problem comes when such a virus from the oral vaccine spreads among too many people and regains its ability to cause paralytic polio.