A fractional two-dose regimen of the polio vaccine presents a low-cost alternative to the current schedule

Feb 10th – Seroconversion or priming of the immune response occurred in 90% of the infants after a single dose of inactivated polio vaccine (IPV).

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1. After a single dose of IPV, either seroconversion or priming of the immune response occurred in 90% of the infants.

2. After 2 doses of IPV, greater than 90% of infants seroconverted with high antibody titers.

The purpose of this study was to evaluate the use of a two-dose schedule of inactivated polio vaccine (IPV) to see whether it could be cost-effective in this post-eradication era of polio. The authors found that after a single dose of IPV, more than 90% of the infants either seroconverted or showed priming of the immune system. After two doses of either the fractional or full dose, more than 90% of the infants had seroconverted displaying high antibody titers to types 1 to 3 of the poliovirus. This schedule reduces the number of visits to a provider from 4 to 2 and reduces the price of IPV from $6 per vaccine to $1.20 per vaccine.

Although this trial showed promising data in reducing the cost of polio prevention, there are still many limitations to this study. The study was performed in only one country and only in 310 infants, which is quite low for a study looking at the efficacy of a vaccine. Furthermore, the investigators followed the infants for only 30 days after the second dose of vaccine was given. Future studies should look at how long detectable antibodies persist. Nevertheless, this study indicates that a two-dose schedule of a fractional polio vaccine can be a low-cost alternative to current practices in the post-eradication era.

Click to read the study in NEJM

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Image: PD

1. After a single dose of IPV, either seroconversion or priming of the immune response occurred in 90% of the infants.

2. After 2 doses of IPV, greater than 90% of infants seroconverted with high antibody titers.

This [randomized control] study compared the use of a two fractional dose regimen of inactivated polio vaccine (IPV) to a two full doses of IPV in 310 infants at age 4 and 8 months. Seroconversion was defined as a 4-fold increase in antibody titer compared to baseline. Priming was defined as having an absence of seroconversion after the first dose, but 4 times the antibody titer 7 days after the second dose.

The study showed that after a single dose, seroconversion was significantly increased in infants receiving the full dose compared to fractional dose. However, the fractional dose was equality effective in priming the immune response. After the second dose, more than 90% of the infants servoconverted with high antibody titers in both groups. There were significantly more adverse events in the fractional dose group; these were relatively minor reactions (redness and induration) and a result of administering the vaccine intradermally instead of intramuscularly.

In sum: The purpose of this study was to evaluate the use of a two-dose schedule of inactivated polio vaccine (IPV) to see whether it could be cost-effective in this post-eradication era of polio. The authors found that after a single dose of IPV, more than 90% of the infants either seroconverted or showed priming of the immune system. After two doses of either the fractional or full dose, more than 90% of the infants had seroconverted displaying high antibody titers to types 1 to 3 of the poliovirus. This schedule reduces the number of visits to a provider from 4 to 2 and reduces the price of IPV from $6 per vaccine to $1.20 per vaccine.

Although this trial showed promising data in reducing the cost of polio prevention, there are still many limitations to this study. The study was performed in only one country and only in 310 infants, which is quite low for a study looking at the efficacy of a vaccine. Furthermore, the investigators followed the infants for only 30 days after the second dose of vaccine was given. Future studies should look at how long detectable antibodies persist. Nevertheless, this study indicates that a two-dose schedule of a fractional polio vaccine can be a low-cost alternative to current practices in the post-eradication era.

Click to read the study in NEJM

By Jeremy Chan and Mitalee Patil

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