Fractional doses of inactivated poliovirus vaccine in Oman.
BACKGROUND
We conducted a clinical trial of fractional doses of inactivated poliovirus vaccine administered to infants in Oman, in order to evaluate strategies for making the vaccine affordable for use in developing countries.


METHODS
We compared fractional doses of inactivated poliovirus vaccine (0.1 ml, representing one fifth of a full dose) given intradermally with the use of a needle-free jet injector device, with full doses of vaccine given intramuscularly, with respect to immunogenicity and reactogenicity. Infants were randomly assigned at birth to receive either a fractional dose or a full dose of inactivated poliovirus vaccine at 2, 4, and 6 months. We also administered a challenge dose of monovalent type 1 oral poliovirus vaccine at 7 months and collected stool samples before and 7 days after administration of the challenge dose.


RESULTS
A total of 400 infants were randomized, of whom 373 (93.2%) fulfilled the study requirements. No significant baseline differences between the groups were detected. Thirty days after completion of the three-dose schedule, the rates of seroconversion to types 1, 2, and 3 poliovirus were 97.3%, 95.7%, and 97.9%, respectively, in the fractional-dose group, as compared with 100% seroconversion to all serotypes in the full-dose group (P=0.01 for the comparison with respect to type 2 poliovirus; results with respect to types 1 and 3 poliovirus were not significant). The median titers were significantly lower in the fractional-dose group than in the full-dose group (P<0.001 for all three poliovirus serotypes). At 7 months, 74.8% of the infants in the fractional-dose group and 63.1% of those in full-dose group excreted type 1 poliovirus (P=0.03). Between birth and 7 months, 42 hospitalizations were reported, all related to infectious causes, anemia, or falls, with no significant difference between vaccination groups.


CONCLUSIONS
These data show that fractional doses of inactivated poliovirus vaccine administered intradermally at 2, 4, and 6 months, as compared with full doses of inactivated poliovirus vaccine given intramuscularly on the same schedule, induce similar levels of seroconversion but significantly lower titers. (Current Controlled Trials number, ISRCTN17418767.)
Mohammed
Ali Jafer
AJ
Ministry of Health, Oman.
AlAwaidy
Salah
S
Bawikar
Shyam
S
Kurup
Padmamohan J
PJ
Elamir
Emadaldin
E
Shaban
Mahmoud M A
MM
Sharif
Sharif M
SM
van der Avoort
Harrie G A M
HG
Pallansch
Mark A
MA
Malankar
Pradeep
P
Burton
Anthony
A
Sreevatsava
Meghana
M
Sutter
Roland W
RW
D000914:Antibodies, Viral / Q000096:biosynthesis; D003906:Developing Countries; D005260:Female; D006801:Humans; D056724:Immunity, Humoral; D018928:Immunity, Mucosal; D007223:Infant; D007271:Injections, Intradermal; D007273:Injections, Intramuscular; D007277:Injections, Jet; D008297:Male; D009850:Oman; D011051:Poliomyelitis / Q000517:prevention & control*; D017955:Poliovirus / Q000276:immunology; D011054:Poliovirus Vaccine, Inactivated / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology*; D014611:Vaccination / Q000009:adverse effects
D000914:Antibodies, Viral; D011054:Poliovirus Vaccine, Inactivated