Expanding age groups for polio SIAs could increase population immunity
Researchers from the nonprofit organization Kid Risk, Inc., explored the potential role of including older children and adults in SIAs to increase population immunity and prevent or stop polio transmission. The research team used a differential equation-based dynamic poliovirus transmission model to analyze the vaccine resource implications and the epidemiological impact of expanding target age groups for SIAs.
SIAs with expanded age groups were able to decrease transmission, reduce overall caseloads and led to a small reduction in the time to achieve WPV elimination, according to the study.
The researchers examined how the use of older age groups in SIAs would impact three situations: retrospective and prospective acceleration elimination in endemic northwestern Nigeria, retrospective examination of elimination in northern India and alternative responses to the 2010 outbreak in Tajikistan.
The team found the greatest benefits of preventive expanded age group SIAs in Tajikistan, India and Nigeria when administered prior to type-specific surges in incidence. The SIAs demonstrated relatively less benefit in outbreak situations or when used to accelerate the interruption of endemic transmission.
The researchers found that the effectiveness of expanded SIAs for Nigeria and India would depend on how well SIAs with expanded age groups were able to reach relatively isolated subpopulations.
The study found that policymakers should carefully consider the epidemiological situation when deciding to use expanded age group SIAs.