Injected polio vaccine to boost immunity
15 Jul 2014 by Evoluted New Media
A type of polio vaccine that fell out of favour in the 1960s could hasten the eradication of the disease.
A study published in The Lancet suggests that the injected polio vaccine (IPV) could provide better and long-lasting protection against infection that the commonly used live oral polio vaccine (OPV).
“Because IPV is injected into the arm, rather than taken orally, it’s been assumed that it doesn’t provide much protection in the gut and so would be less effective at preventing faecal transmission than OPV,” said Dr Jacob John, Associate Professor at the Christian Medical College in India.
“However, we found that where the children already had a level of immunity due to OPV, the injected vaccine actually boosted their gut immunity.”
The study involved 450 children from a densely populated urban area in Vellore, India who had received the OPV as part of a standard vaccination program. Half were given a dose of the IPV and half nothing.
A month later, the children were given a ‘challenge’ dose of the live oral vaccine to simulate reinfection. After seven days, their stools were tested for signs of the virus, specifically serotypes 1 and 3 which are resisting eradication.
In children who received the IPV, researchers found 38% fewer had serotype 1 in their stool, and 70% fewer had serotype 3 compared to those not given the injection.
“Our findings show that an additional dose of the injected vaccine is more effective at boosting immunity against infection than the oral vaccine alone,” said Nick Grassly, Professor of Vaccine Epidemiology at Imperial College London and senior author of the study.
“This implies that the IPV could be used to boost immunity in people travelling from or to polio-infected countries such as Afghanistan, Pakistan and Nigeria. It could also replace some of the OPV doses in immunisation campaigns to boost gut immunity, particularly in areas of poor sanitation.”
A second study in PNAS saw Imperial researchers investigating whether expanding the range of vaccination campaigns to include older children and adults could prevent transmission. A mathematical model examining outbreaks in Tajikistan and the Republic of Congo in 2010 found older ages contributed significantly to transmission in the latter, and could be related to sanitation standards. Launching mass immunisation campaigns more quickly in response to outbreaks would have a greater impact than expanding the age range, the report said.
The role of older children and adults in wild poliovirus transmission
