A Call for Global Transition from Oral Polio Vaccine to Inactivated Poliovirus Vaccine

Background: The Global Polio Eradication Initiative (GPEI) is facing two formidable obstacles. Wild poliovirus (WPV) type 1 continues to cause polio in Afghanistan and Pakistan, where, in 2024, there were 93 cases, despite some children receiving over 15 doses of Oral Polio Vaccine (OPV), highlighting suboptimal vaccine efficacy (VE). Genetic variants of vaccine polioviruses viz., circulating vaccine-derived polioviruses (cVDPVs), continue to cause polio. In 2024, there were 253 cases in these same two countries, Afghanistan and Pakistan, highlighting OPV’s serious safety problem. No other childhood vaccine has such a bleak record. Methods: We analysed annual numbers of polio reported by the GPEI during 2008-2024. GPEI does not permit public access to the annual numbers of vaccine-associated paralytic polio (VAPP) cases, polio caused by non-circulating vaccine-derived poliovirus known as ambiguous VDPV (aVDPV) and polio due to immunodeficiency-related VDPV (iVDPV). Therefore, we have estimated their numbers based on a review of publications that counted cases for research purposes; we then extrapolated to arrive at a global figure. Results: Globally the number of iatrogenic polio cases surpassed that of WPV polio in 2012 and cVDPV polio alone surpassed that of WPV polio in 2017. In the last 7 years (2018-2024), the total of 489 WPV cases and 3,955 cVDPV cases show that there were eight cVDPV polio cases for every case of WPV polio. With the estimated total of 4347 cases of iatrogenic polio (VAPP, iVDPV, aVDPV and cVDPV cases), the ratio is nearly nine cases caused by vaccine polioviruses and their variants for every case of WPV polio. Conclusion: The continued use of OPV is associated with an approximate nine-fold increased risk of iatrogenic polio in comparison with endemic WPV-1 polio, during 2018-2024. Therefore, its continued use is unjustified because of sub-optimal VE and serious safety problems. Risk-free protection from polio can be provided with use of inactivated poliovirus vaccine (IPV) which has near-100% VE for three doses. Giving IPV under the Expanded Programme on Immunization, followed by the discontinuation of OPV, is the right way forward to achieve and sustain polio eradication globally.