Transmission of Imported Vaccine-Derived Poliovirus in an Undervaccinated Community in Minnesota

MAJOR ARTICLE Transmission of Imported Vaccine-Derived Poliovirus in an Undervaccinated Community in Minnesota James P. Alexander,1 Kristen Ehresmann,2 Jane Seward,1 Gary Wax,2,a Kathleen Harriman,2,a Susan Fuller,2 Elizabeth A. Cebelinski,2 Qi Chen,1 Jaume Jorba,1 Olen M. Kew,1 Mark A. Pallansch,1 M. Steven Oberste,1 Mark Schleiss,3 Jeffrey P. Davis,4 Bryna Warshawsky,5 Susan Squires,6 and Harry F. Hull,2,a for the Vaccine-Derived Poliovirus Investigations Groupb 1 National Center for Immunizations and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; 2Minnesota Department of Health, St. Paul, and 3University of Minnesota School of Medicine, Minneapolis; 4Division of Public Health, Wisconsin Department of Health and Family Services, Madison; 5Middlesex–London Health Unit, London, and 6Public Health Agency of Canada, Ottawa, Ontario, Canada Background. Oral poliovirus vaccine (OPV) has not been used in the United States since 2000. Type 1 vaccinederived poliovirus (VDPV) was identified in September 2005, from an unvaccinated Amish infant hospitalized in Minnesota with severe combined immunodeficiency. An investigation was conducted to determine the source of the virus and its means of transmission. Methods. The infant was tested serially for poliovirus excretion. Investigations were conducted to detect poliovirus infections or paralytic poliomyelitis in Amish communities in Minnesota, neighboring states, and Ontario, Canada. Genomic sequences of poliovirus isolates were determined for phylogenetic analysis. Results. No source for the VDPV could be identified. In the index community, 8 (35%) of 23 children tested, including the infant, had evidence of type 1 poliovirus or VDPV infection. Phylogenetic analysis suggested that the VDPV circulated in the community for ⬃2 months before the infant’s infection was detected and that the initiating OPV dose had been given before her birth. No paralytic disease was found in the community, and no poliovirus infections were found in other Amish communities investigated. Conclusions. This is the first demonstrated transmission of VDPV in an undervaccinated community in a developed country. Continued vigilance is needed in all countries to identify poliovirus infections in communities at high risk of poliovirus transmission. Because of successful vaccination programs, endemic poliomyelitis was eliminated from the United States by the mid-1970s. In 1979, after importation of wild poliovirus, the last US polio outbreak occurred in unvaccinated Amish communities, involving 13 cases of paraReceived 17 July 2008; accepted 27 August 2008; electronically published 17 December 2008. Potential conflicts of interest: none reported. Presented in part: National Vaccine Advisory Committee, Washington, DC, 8 February 2006; National Immunization Conference, Atlanta, 7 March 2006. Financial support: none reported. a Present affiliations: California Department of Public Health, Immunization Branch, Epidemiology and Surveillance Section, Richmond (K.H.); HF Hull Associates, St. Paul, Minnesota (H.F.H.); HealthEast Care System, St. Joseph’s Hospital, St. Paul, Minnesota (G.W.). b Study group members are listed after the text. Reprints or correspondence: Dr. James Alexander, 1600 Clifton Rd. NE, Mail Stop E-05, Atlanta, GA 30333 (). The Journal of Infectious Diseases 2009; 199:391–7 © 2008 by the Infectious Diseases Society of America. All rights reserved. 0022-1899/2009/19903-0014$15.00 DOI: 10.1086/596052 lytic disease in 3 states and subclinical infections in 3 other states as well as 2 cases of paralytic disease in Ontario, Canada [1, 2]. From 1980 to 1997, a mean of 9 reported paralytic poliomyelitis cases occurred annually in the United States [3, 4]. Nearly all were vaccineassociated paralytic polio (VAPP), underscoring the ongoing risk associated with oral poliovirus vaccine (OPV), estimated to be 1 case of VAPP per 2.9 million doses distributed [4]. As the occurrence of wild poliovirus importations declined to only 5 in the 1980s and to 2 in the 1990s [3, 4], the risk-benefit equation changed in favor of using inactivated poliovirus vaccine (IPV) routinely. From 1997 to 2000, the transition in vaccination policy from an all-OPV to an all-IPV schedule eliminated VAPP in the United States; the last endemically acquired case of VAPP occurred in 1999 [4 – 6]. In addition to causing VAPP, OPV use is also associated with the rare occurrence of genetically drifted Vaccine-Derived Poliovirus Type 1 in the US ● JID 2009:199 (1 February) ● 391 vaccine-derived polioviruses (VDPVs) that can circulate in undervaccinated populations (circulating VDPVs [cVDPVs]) or cause persistent infections in immunodeficient individuals (immunodeficiency-related VDPVs [iVDPVs]) [7–9]. In September 2005, a poliovirus infection in an unvaccinated Amish infant was identified by the Minnesota Department of Health and reported to the Centers for Disease Control and Prevention. The virus was identified as type 1 VDPV. The present report describes the epidemiologic and laboratory investigations and control efforts regarding the first VDPV with community transmission detected in the United States. METHODS 392 ● JID 2009:199 (1 February) ● Alexander et al. Index patient investigation. We reviewed the infant’s medical, family, and social history to identify potential sources for exposure to polioviruses. We confirmed the infant’s VDPV infection and monitored her for ongoing excretion of VDPVs during treatment of the underlying immunodeficiency, using approximately weekly testing (from late September 2005 through January 2006) of serum samples for neutralizing antibody to polioviruses and of stool specimens for VDPVs. Hospital and health care investigations and interventions. In October 2005, we conducted investigations at the 4 hospitals (hospitals 1– 4) to which the infant had been admitted, to determine whether she had been infected in the health care setting or whether her infection had been transmitted to others. Hospital staff offered IPV to health care workers and patients with recent or ongoing exposure who were not current for polio vaccination [6]. At hospitals 1–3, where the infant had been admitted during July–August 2005, hospital infection control staff reviewed health care worker and patient records to identify contacts. We surveyed contact health care workers and infection control staff reviewed contact patient records regarding relevant recent illness and immunologic status. At hospital 4, where the infant remained hospitalized in October 2005, we surveyed staff who reported exposure to the infant or her environment without the use of contact precautions regarding polio vaccination status, immunologic status, and recent illnesses in themselves or family members. Hospital staff collected stool specimens from potentially exposed staff and from patients who were located in the same medical units as the infant. To id (...truncated)