Fractional dose of inactivated poliovirus can induce priming

Twenty percent of a full dose of inactivated polio virus produced significant priming and seroconversion in infants, demonstrating a potential method for reducing polio immunization base costs, according to a recent study.

Cuban researchers compared the immunogenicity and reactogenicity of the fractional dose of IPV administered intradermally with a full dose administered intramuscularly in Cuban infants between four months and eight months of age. Using fractional doses of IPV could reduce the costs of maintaining a base of polio immunization in low-income areas, the New England Journal of Medicine reports.

The study authors collected blood from infants at the ages of four months, eight months, eight months and seven days, and eight months and 30 days to assess single-dose seroconversion, single-dose priming of immune responses and two-dose seroconversion.

The group receiving the first fractional dose experienced seroconversion to poliovirus types one, two and three of 16.6 percent, 47.1 percent and 14.7 percent, respectively, compared to 46.6 percent, 62.8 percent and 32.0 percent in the group receiving the first full dose. A priming immune response to the three poliovirus types was 90.8 percent, 94.0 percent and 89.6 percent, respectively, in the group with the fractional dose, compared to 97.6 percent, 98.3 percent and 98.1 percent in the full dose group.

After the administration of the second IPV dose, the fractional dose group experienced a cumulative two-dose seroconversion to the three poliovirus types of 93.6 percent, 98.1 percent and 93.0 percent, respectively, compared to 100 percent, 100 percent and 99.4 percent in the group with the full dose, the New England Journal of Medicine reports.

The authors concluded that vaccinating infants with a single fractional IPV dose can induce priming and seroconversion in more than 90 percent of immunized infants.

The study was funded by the Pan American Health Organization and the World Health Organization.