Why the study?
Since May 2019, the Central African Republic has experienced a poliomyelitis outbreak caused by serotype 2 vaccine-derived polioviruses, prompting analysis to ascertain the origin of these strains.
The 2019 VDPV-2 outbreak in the Central African Republic resulted from multiple independent emergence events of recombinant vaccine-derived strains that circulated silently for months to years.
P oliomyelitis results from infection of the central nervous system by poliovirus, a picornavirus of the species Enterovirus C (1). The Global Polio Eradication Initiative (https://polioeradication.org) managed to eradicate wild poliovirus of 2 of the 3 serotypes and to contain virus of the third serotype in Pakistan and Afghanistan. The Initiative relies on 2 pillars: surveillance of poliovirus circulation and vaccination. Contrary to the inactivated polio vaccine, the oral polio vaccine (OPV) induces strong intestinal immunity that blocks transmission of poliovirus in subsequent infections (2). Consequently, OPV is currently the only tool capable of stopping poliovirus transmission. However, because attenuated strains of OPV replicate in the gut and are excreted in feces, low vaccine coverage enables circulation of these strains and loss of their attenuated phenotype through genetic drift (3,4). Since May 2019, the Central African Republic (CAR) has experienced a poliomyelitis outbreak caused by serotype 2 vaccine-derived polioviruses (VDPV-2s). To ascertain the origin of these VDPV-2s, we determined and analyzed their full-length genomic sequences.
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Joffret et al. (2021) studied this question.
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