Immunogenicity of Intramuscular Fractional Dose of Inactivated Poliovirus Vaccine.

BACKGROUNDS

Intradermal (id) fractional inactivated poliovirus vaccine ([fIPV] one fifth of normal IPV dose) is safe and immunogenic; however, id administration is perceived as difficult. We compared fIPV immunogenicity administered id or intramuscularly (im).

METHODS

This noninferiority trial was conducted among polio vaccine-naive Cuban infants who received 2 IPV doses at 4 and 8 months of age. Infants were randomized into 4 arms: (A) fIPV, 0.1 mL im; (B) fIPV, 0.2 mL im; (C) fIPV, 0.1mL id; and (D) IPV, 0.5 mL im. Blood collected before and after vaccinations was tested for poliovirus-neutralizing antibodies.

RESULTS

A total of 196 of 214 (91.6%) enrolled children completed study. Seroconversion after 2 IPV doses in each arm were as follows: (A) 97.3% (90.6-99.7), 98.7% (92.7-99.9), and 90.5% (81.5-96.1) for serotypes 1, 2, and 3, respectively; (B) 97.2% (90.3-99.7), 100%, 95.8% (88.3-99.1) for serotypes 1, 2, and 3, respectively; (C) 89.3% (71.8-97.7), 92.9% (76.5-99.1), 82.1% (63.1-93.9) for serotypes 1, 2, and 3, respectively; and (D) 100%, 100%, 100% for serotypes 1, 2, and 3, respectively. Seroconversion with fIPV im was noninferior to fIPV id for all serotypes.

CONCLUSIONS

We demonstrated noninferiority of fIPV im compared with id when administered at 4 and 8 months of age. Further investigations in an earlier infant schedule should be pursued to explore fIPV im as option for dose-sparing strategy in countries reluctant to use fIPV id due to programmatic difficulties of id administration.