Polio eradication remains a challenge

Seroprevalence of antipolio antibodies among children <15 years of age in border provinces in China

Despite remarkable progression toward polio eradication worldwide, wild poliovirus (WPV) importation has been a great challenge for China, as it shares borders with countries where WPV is endemic. The objective of this study was to estimate poliovirus antibody seroprevalence among children <15 years of age in 3 border provinces (Yunnan Province, Tibet Autonomous Region, and Xinjiang Uygur Autonomous Region) in China. A cross-sectional, hospital-based study was undertaken in 3 border provinces in 2010. Individuals <15 years old who visited hospitals at the prefecture level or above to have their blood drawn for any reason were invited to participate in our study. Neutralizing antibody titers to polio serotypes 1 (P1), P2, and P3 were assayed according to the World Health Organization manual for the virological investigation of polio. Antibody titers of ≥8 were considered positive. Among the 1,360 subjects enrolled, 1,220 (89.7%), 1,259 (92.6%), and 1,112 (81.8%) were seropositive to P1, P2, and P3, respectively, and 1,051 (77.3%) subjects were seropositive to all three serotypes. The highest seropositive rates were observed in Xinjiang Uygur Autonomous Region. By age, 3- to 5-year-old subjects had the highest rate of seropositivity, and seropositivity decreased significantly with increasing age. The risk of WPV importation will continue until WPV transmission has been interrupted worldwide. Consistent with the Global Polio Eradication Initiative's polio endgame strategy, China must maintain its polio-free status by ensuring adequate population immunity against polio. Because immunity wanes with increasing age, a booster dose with bivalent type 1 and 2 oral poliovirus vaccine could be considered for teenagers in China.

Monitoring of poliovirus neutralizing antibodies in São Paulo State, Brazil

As the world envisions poliomyelitis eradication, objective parameters are needed to ascertain whether immunocompetence against the virus provided by vaccine campaigns has been attained. The presence of neutralizing antibodies is considered a surrogate marker of protective immune response to the agent. Neutralization of three poliovirus serotypes were evaluated in a total of 411 sera samples collected from 1999 to 2005 in São Paulo State, Brazil. Antibody titres >/=1:8 were presented at 88.1% (362/411), 88.8% (365/411) and 61.6% (253/411) of samples for 1, 2 and 3 serotypes, respectively. Evaluation of poliovirus immune status may be a useful tool to support decisions concerning polio vaccine policy.