Serologic response to inactivated poliovirus vaccine: a randomized clinical trial comparing 2 vaccination schedules in Puerto Rico.
BACKGROUND
The World Health Organization (WHO) recommends the discontinuation of oral poliovirus vaccine after eradication of wild poliovirus. Studies assessing inactivated poliovirus vaccine (IPV) immunogenicity in tropical countries, using the WHO Expanded Programme on Immunization (EPI) schedule, have been limited.


METHODS
We conducted a randomized clinical trial in Ponce, Puerto Rico. Infants were assigned to 1 of 2 study arms: those in the EPI arm received IPV at 6, 10, and 14 weeks of age, and those in the US arm received IPV at 2, 4, and 6 months of age. Neutralizing antibody titers against poliovirus types 1, 2, and 3 were tested on serum specimens obtained before administration of the first dose of IPV and 28-45 days after administration of the last dose of IPV.


RESULTS
Seroconversion rates for the EPI (n=225) and US (n=230) arms, respectively, were 85.8% and 99.6% for poliovirus type 1 (P<.001), 86.2% and 100% for poliovirus type 2 (P<.001), and 96.9% and 99.1% for poliovirus type 3 (P=.08). Seroconversion rates were lower among infants in the EPI arm who had high maternal antibody levels for all 3 poliovirus types (P<.001).


CONCLUSIONS
The EPI schedule resulted in lower seroconversion rates for poliovirus types 1 and 2. These results are relevant for tropical countries planning to use IPV in a posteradication environment.
Dayan
Gustavo H
GH
Division of Viral Diseases, National Center for Immunization and Respiratory Diseases (proposed), Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. gdayan@cdc.gov
Thorley
Margaret
M
Yamamura
Yasuhiro
Y
Rodríguez
Nayra
N
McLaughlin
Steve
S
Torres
Lourdes M
LM
Seda
Antonio
A
Carbia
Marcia
M
Alexander
Lorraine N
LN
Caceres
Victor
V
Pallansch
Mark A
MA
D000914:Antibodies, Viral / Q000096:biosynthesis / Q000097:blood*; D005260:Female; D006801:Humans; D007112:Immunity, Maternally-Acquired / Q000276:immunology; D007115:Immunization Schedule; D007223:Infant; D008297:Male; D011054:Poliovirus Vaccine, Inactivated / Q000008:administration & dosage / Q000276:immunology*; D011055:Poliovirus Vaccine, Oral / Q000008:administration & dosage / Q000276:immunology*; D011647:Puerto Rico; D016036:Seroepidemiologic Studies
D000914:Antibodies, Viral; D011054:Poliovirus Vaccine, Inactivated; D011055:Poliovirus Vaccine, Oral