Reduced dose of polio vaccine feasible in low-income areas

By Sally Robertson, B.Sc.Feb 4 2013

Vaccinating infants with a single fractional dose of inactivated poliovirus (IPV) is an effective and more affordable alternative to using multiple full doses, report researchers in the New England Journal of Medicine.

"Vaccinating infants with a single fractional dose of IPV can induce priming and seroconversion in more than 90% of immunized infants," say Roland Sutter (World Health Organization, Geneva, Switzerland) and colleagues.

In a clinical trial conducted at 13 vaccination sites in Cuba, 310 infants were randomly allocated to receive either a fractional dose of IPV (one fifth of the full dose) or a full dose at age 4 and 8 months. Fractional doses were administered intradermally and full doses intramuscularly.

After the first dose of IPV, antibodies to poliovirus types 1, 2, and 3 developed in 16.6%, 47.1%, and 14.7% of the fractional dose group, respectively, and in 46.6%, 62.8%, and 32.0% of the full-dose group.

A priming response to poliovirus type 1, 2, and 3 was met in 90.8%, 94.0%, and 89.6% of the fractional dose group and in 97.6%, 98.3%, and 98.1% of the full-dose group, respectively.

After the second dose of IPV, the cumulative rates of seroconversion to poliovirus types 1, 2, and 3 were 93.6%, 98.1%, and 93.0% in the fractional dose group and 100%, 100%, and 99.4% in the full-dose group, respectively.

There were 114 adverse events in the fractional dose group and 11 in the full-dose group. However, these were classified as minor, with the most common ones redness at the injection site, induration at the injection site, and raised temperature.

The team says two fractional doses of IPV administered on an appropriate schedule, with the first dose not administered before the age of 2 months, and at least 2 months between doses, would reduce the cost of each vaccination from the current price of US$ 6.00 (€ 4.40) to US$ 1.20 (€ 0.88). Furthermore, a one-dose IPV priming schedule could further reduce the cost to 60 cents (€ 0.44).

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