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Effect of different immunisation schedules on the excretion and reversion of oral poliovaccine strains.

Minor PD, Dunn G, Ramsay ME, Brown D

National Institute for Biological Standards and Control, Blanche Lane South Mimms, Potters Bar, Herts, EN6 3QG, UK. pminor@nibsc.ac.uk

Excretion of live oral poliovaccine and molecular markers of increased virulence in the viruses isolated were examined in children who were either previously immunised with inactivated or live vaccine or were unimmunised. There appeared to be some effect of previous immunisation with either live or killed vaccine at the second dose of live vaccine. Where an effect was seen it took the form of reduced rates of excretion, shorter time periods of excretion and more rapid and complete reversion of the excreted virus. The data are consistent with the view that poliovirus is able to escape the immune pressure in the gut to some extent by improving its general fitness rather than direct evasion of immunity.

Published 23 November 2004 in J Med Virol, 75(1): 153-60.
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