Britain began vaccinating against polio in 1955 and moved to a live oral vaccine in 1961, which allowed the virus to grow in the human gut, offering almost complete protection.
While polio was still spreading in the community the live vaccine was considered preferable specifically because the virus could pass from person to person, so the live vaccine enhanced immunity and ensured people picked it up when young when they were less likely to be paralysed.
But after the eradication of polio, Britain moved to an injectable inactivated vaccine in 2004, which does not shed into the sewage system, stopping spread. It means that any vaccine-derived virus must have come from abroad.
https://www.telegraph.co.uk/news/2022/06/22/polio-back-national-incident-declared-uk-disease-spreads-first/Back in 1992 before I traveled to Egypt with my mom, we were told we needed a Polio booster. We laughed because we had the original series (and my mom got it as a young adult when it was first available in the '50s), but we apparently ended up getting what I am realizing was the OPV version (a liquid of the live virus or perhaps it was attenuated), which is obviously not done in the U.S. anymore as that has been replaced with the IPV shot now.
And I found this that apparently explains my 1992 experience -
Vaccine Policy Changes and Epidemiology of Poliomyelitis in the United States
Lorraine Niño Alexander, RN, MPH; Jane F. Seward, MBBS, MPH; Tammy A. Santibanez, PhD; et al Mark A. Pallansch, PhD; Olen M. Kew, PhD; D. Rebecca Prevots, PhD; Peter M. Strebel, MD; Joanne Cono, MD, ScM; Melinda Wharton, MD; Walter A. Orenstein, MD; Roland W. Sutter, MD
Author Affiliations Article Information
JAMA. 2004;292(14):1696-1701. doi:10.1001/jama.292.14.1696
Abstract
Context The last case of poliomyelitis in the United States due to indigenously acquired wild poliovirus occurred in 1979; however, as a consequence of oral poliovirus vaccine (OPV) use that began in 1961, an average of 9 cases of vaccine-associated paralytic poliomyelitis (VAPP) were confirmed each year from 1961 through 1989.
To reduce the VAPP burden, national vaccination policy changed in 1997 from reliance on OPV to options for a sequential schedule of inactivated poliovirus vaccine (IPV) followed by OPV. In 2000, an exclusive IPV schedule was adopted.
Objective To review the epidemiology of paralytic poliomyelitis and document the association between the vaccine schedule changes and VAPP in the United States.
(snip)
Results From 1990 through 1999, 61 cases of paralytic poliomyelitis were reported; 59 (97%) of these were VAPP (1 case per 2.9 million OPV doses distributed), 1 case was imported, and 1 case was indeterminate. Thirteen cases occurred during the 1997-1999 transitional policy period and were associated with the all-OPV schedule; none occurred with the IPV-OPV schedule. No cases occurred after the United States implemented the all-IPV policy in 2000. The last imported poliomyelitis case occurred in 1993 and the last case of VAPP occurred in 1999.
(snip)
https://jamanetwork.com/journals/jama/fullarticle/199583
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