Guidance for Assessment of Poliovirus Vaccination Status and Vaccination of Children Who Have Received Poliovirus Vaccine Outside the United States.

In 1988, the World Health Assembly resolved to eradicate poliomyelitis (polio). Since then, wild poliovirus (WPV) cases have declined by >99.9%, from an estimated 350,000 cases of polio each year to 74 cases in two countries in 2015 (1). This decrease was achieved primarily through the use of trivalent oral poliovirus vaccine (tOPV), which contains types 1, 2, and 3 live, attenuated polioviruses. Since 2000, the United States has exclusively used inactivated polio vaccine (IPV), which contains all three poliovirus types (2,3). In 2013, the World Health Organization (WHO) set a target of a polio-free world by 2018 (4). Of the three WPV types, type 2 was declared eradicated in September 2015. To remove the risk for infection with circulating type 2 vaccine-derived polioviruses (cVDPV), which can lead to paralysis similar to that caused by WPV, all OPV-using countries simultaneously switched in April 2016 from tOPV to bivalent OPV (bOPV), which contains only types 1 and 3 polioviruses (5). This report summarizes current Advisory Committee on Immunization Practices (ACIP) recommendations for poliovirus vaccination and provides CDC guidance, in the context of the switch from tOPV to bOPV, regarding assessment of vaccination status and vaccination of children who might have received poliovirus vaccine outside the United States, to ensure that children living in the United States (including immigrants and refugees) are protected against all three poliovirus types. This guidance is not new policy and does not change the recommendations of ACIP for poliovirus vaccination in the United States. Children living in the United States who might have received poliovirus vaccination outside the United States should meet ACIP recommendations for poliovirus vaccination, which require protection against all three poliovirus types by age-appropriate vaccination with IPV or tOPV. In the absence of vaccination records indicating receipt of these vaccines, only vaccination or revaccination in accordance with the age-appropriate U.S. IPV schedule is recommended. Serology to assess immunity for children with no or questionable documentation of poliovirus vaccination will no longer be an available option and therefore is no longer recommended, because of increasingly limited availability of antibody testing against type 2 poliovirus.

H1PVAT is a novel and potent early-stage inhibitor of poliovirus replication that targets VP1.

A novel small molecule, H1PVAT, was identified as a potent and selective inhibitor of the in vitro replication of all three poliovirus serotypes, whereas no activity was observed against other enteroviruses. Time-of-drug-addition studies revealed that the compound interfered with an early stage of virus replication. Four independently-selected H1PVAT-resistant virus variants uniformly carried the single amino acid substitution I194F in the VP1 capsid protein. Poliovirus type 1 strain Sabin, reverse-engineered to contain this substitution, proved to be completely insensitive to the antiviral effect of H1PVAT and was cross-resistant to the capsid-binding inhibitors V-073 and pirodavir. The VP1 I194F mutant had a smaller plaque phenotype than wild-type virus, and the amino acid substitution rendered the virus more susceptible to heat inactivation. Both for the wild-type and VP1 I194F mutant virus, the presence of H1PVAT increased the temperature at which the virus was inactivated, providing evidence that the compound interacts with the viral capsid, and that capsid stabilization and antiviral activity are not necessarily correlated. Molecular modeling suggested that H1PVAT binds with high affinity in the pocket underneath the floor of the canyon that is involved in receptor binding. Introduction of the I194F substitution in the model of VP1 induced a slight concerted rearrangement of the core ß-barrel in this pocket, which disfavors binding of the compound. Taken together, the compound scaffold, to which H1PVAT belongs, may represent another promising class of poliovirus capsid-binding inhibitors next to V-073 and pirodavir. Potent antivirals against poliovirus will be essential in the poliovirus eradication end-game.

Environmental Surveillance in Kenya

Poliovirus surveillance is one of three key strategies adopted by the WHO Global Polio Eradication Initiative (PEI). The detection and investigation of acute flaccid paralysis (AFP) cases is the gold standard for the detection of polioviruses but can be supplemented by poliovirus detection in close contacts of AFP cases and in environmental samples. Detection of wild poliovirus (WPV) from environmental samples can point to silent transmission and aid in targeting immunization responses to interrupt further spread.1 This article reports the experience of environmental surveillance in Nairobi; Kenya