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Inactivated Poliovirus Vaccine Immunogenic in Cuban Infants

IPV produced high seroconversion rates for poliovirus types 1 and 3, but lower rates for type 2.

After transmission of wild poliovirus is stopped, global use of live oral poliovirus vaccine (OPV) should cease, to avoid the emergence of neurovirulent vaccine-derived virus with potential for transmission. But will inactivated poliovirus vaccine (IPV) be immunogenic in tropical developing countries that have relied on OPV to control polio?

To find out, investigators in Cuba randomized healthy full-term infants to receive diphtheria-pertussis-tetanus (DPT) and Haemophilus influenzae type b (Hib) vaccines, with or without IPV, in a three-dose schedule (ages 6, 10, and 14 weeks). Another group received DPT-Hib-IPV in a two-dose schedule (ages 8 and 16 weeks). Serum samples were collected before and approximately 4 weeks after the final study-vaccine dose. Infants received a challenge OPV dose during the national vaccination campaign. OPV is given only during twice-yearly campaigns, and the study was scheduled so that IPV vaccination would occur during a period when OPV viruses were absent.

Among the infants who completed the study, seroconversion rates for types 1, 2, and 3 polioviruses were 94%, 83%, and 100%, respectively, for the 52 who received three IPV doses and 90%, 89%, and 90% for the 72 who received two IPV doses. No infants in the non-IPV group seroconverted. Seven days after OPV administration, live poliovirus was isolated from stool specimens of >90% of infants in all three groups, although viral titers were lower for infants who had received IPV. Duration of excretion was not assessed.

Comment: These findings show that IPV is immunogenic against poliovirus types 1 and 3 in infants in a tropical developing country. The authors note that an additional dose might be needed to boost type 2 seroconversion rates (an approach not assessed in this study). Seroconversion rates may be different in regions with ongoing circulation of wild-type or OPV viruses. Additional studies will be needed to inform optimal strategies in the shift from OPV to IPV.

— Mary E. Wilson, MD

Published in Journal Watch Infectious Diseases April 11, 2007

Citation(s):

The Cuba IPV Study Collaborative Group. Randomized, placebo-controlled trial of inactivated poliovirus vaccine in Cuba. N Engl J Med 2007 Apr 12; 356:1536-44.

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