title: Community circulation patterns of oral polio vaccine serotypes 1, 2, and 3 after Mexican national immunization weeks.
abstract: BACKGROUND
  With wild poliovirus nearing eradication, preventing circulating vaccine-derived poliovirus (cVDPV) by understanding oral polio vaccine (OPV) community circulation is increasingly important. Mexico, where OPV is given only during biannual national immunization weeks (NIWs) but where children receive inactivated polio vaccine (IPV) as part of their primary regimen, provides a natural setting to study OPV community circulation.
  
  
  METHODS
  In total, 216 children and household contacts in Veracruz, Mexico, were enrolled, and monthly stool samples and questionnaires collected for 1 year; 2501 stool samples underwent RNA extraction, reverse transcription, and real-time polymerase chain reaction (PCR) to detect OPV serotypes 1, 2, and 3.
  
  
  RESULTS
  OPV was detected up to 7 months after an NIW, but not at 8 months. In total, 35% of samples collected from children vaccinated the prior month, but only 4% of other samples, contained OPV. Although each serotype was detected in similar proportions among OPV strains shed as a result of direct vaccination, 87% of OPV acquired through community spread was serotype 2 (P < .0001).
  
  
  CONCLUSIONS
  Serotype 2 circulates longer and is transmitted more readily than serotypes 1 or 3 after NIWs in a Mexican community primarily vaccinated with IPV. This may be part of the reason why most isolated cVDPV has been serotype 2.
authors.affiliation: Eastern Virginia Medical School, Norfolk, Virginia.
authors.forename: Stephanie B
authors.initials: SB
authors.lastname: Troy
authors.forename: Leticia
authors.initials: L
authors.lastname: Ferreyra-Reyes
authors.forename: Chunhong
authors.initials: C
authors.lastname: Huang
authors.forename: Clea
authors.initials: C
authors.lastname: Sarnquist
authors.forename: Sergio
authors.initials: S
authors.lastname: Canizales-Quintero
authors.forename: Christine
authors.initials: C
authors.lastname: Nelson
authors.forename: Renata
authors.initials: R
authors.lastname: Báez-Saldaña
authors.forename: Marisa
authors.initials: M
authors.lastname: Holubar
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ferreira-Guerrero
authors.forename: Lourdes
authors.initials: L
authors.lastname: García-García
authors.forename: Yvonne A
authors.initials: YA
authors.lastname: Maldonado
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005243:Feces / Q000821:virology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008800:Mexico / Q000453:epidemiology; D009313:National Health Programs; D011051:Poliomyelitis / Q000517:prevention & control* / Q000821:virology; D017955:Poliovirus / Q000302:isolation & purification*; D011055:Poliovirus Vaccine, Oral / Q000276:immunology*; D012424:Rural Population; D014505:Urban Population; D017201:Virus Shedding; D055815:Young Adult
chemical_list: D011055:Poliovirus Vaccine, Oral
keywords: Mexico; VDPV; inactivated polio vaccine; oral polio vaccine; polio