The effect of mass immunisation campaigns and new oral poliovirus vaccines of poliomyelitis in Pakistan and Afghanistan, 2001-11: a retrospective analysis

The researchers conclude that the effectiveness of bivalent OPV is comparable with monovalent OPV and can therefore be used in eradicating serotype 1 poliomyelitis whilst minimising the risks of serotype 3 outbreaks. However, decreases in vaccination coverage in parts of Pakistan and southern Afghanistan have severely limited the effect of this vaccine.