1. Vaccine-Derived Poliovirus Outbreak Minnesota, 2005
Kristen Ehresmann, R.N., M.P.H.
Minnesota Department of Health

2. Acknowledgements Gary Wax Lynn Bahta Claudia Miller Harry Hull
Ruth Lynfield
Kathy Harriman
Jean Rainbow
Elizabeth Cebelinski
Joanne Bartkus
Susan Fuller
Todd County Public Health
And CDC!

3. Adverse Events Related to OPV Vaccination
Vaccine-associated paralytic poliomyelitis (VAPP)
Long term excretion of vaccine-derived polioviruses (VDPV)
Polio outbreaks associated with circulating VDPVs in areas with low rates

4. What is a VDPV?
Vaccine-derived polio viruses (VDPVs) are poliovirus strains derived from one of the three Sabin poliovirus strains in the oral polio vaccine (OPV) that have > 1% difference in nucleotide sequence from the prototype vaccine virus.

5. Types of VDPVs
iVDPV Vaccine-derived polio virus in an immunocompromised individual
cVDPV Vaccine-derived polio virus with sustained person-to-person transmission (community circulation)

6. Background
On September 29, 2006 the Minnesota Department of Health (MDH) identified poliovirus type 1 in an unvaccinated, immunocompromised infant girl aged 7 months in an Amish community whose members predominantly were unvaccinated for polio.

7. Index Patient Unvaccinated, 7 month old Amish girl
Born at home; 3 unvaccinated siblings
Poliovirus type 1 identified in stool sample
No paralysis
Hospitalized for pneumonia at a community hospital in July 2005
Continuously hospitalized since August 22, 2005
Failure to thrive, diarrhea, recurrent infections

8. Index Patient (cont.)
Diagnosis of severe combined immunodeficiency (SCID) made September 15, 2005
Treated with high PV1 titre IVIG with assistance from FDA
Still shedding virus after failed Bone Marrow Transplant (BMT)
Second BMT successful engraftment, no longer shedding virus

9. Community Investigation
Newly formed Amish community in Central MN made up of 24 families
Parents and some elders vaccinated 1979
Visitors from Amish Communities in MN, WI, MI, Ontario including large weddings
No community members with travel outside North America

10. Community Investigation
Simple lifestyle, including use of outhouses
Door-to-door interviews conducted by MDH and local PH staff re: polio vaccination status, immune status, and recent illnesses
Stool samples collected 32 persons/5 households
Serum specimens collected on 7 persons/2 households

11. Hospital Investigation
All 4 hospitals evaluated for nosocomial transmission
At Hospitals 1-3, HCWs interviewed for immune status and recent relevant illnesses in themselves or family members
At Hospital 4, HCWs interviewed for polio vaccine status, immune status and recent relevant illnesses in themselves or family members
Stool samples obtained from potentially exposed patients at Hospital 4 and HCWs

12. Additional Disease Surveillance
AFP surveillance initiated for potential adverse reactions to Menactra
Aseptic meningitis surveillance in Amish counties
National and international notifications regarding the case

13. Outbreak Control Measures
IPV* was offered to
community members
All MN Amish communities
Non-Amish community members
Many adults vaccinated in 1979
IPV offered to staff and patients at Hospital 4
*OPV not available in the US

14. Laboratory Findings
Index case virus: 2.3% divergent from Sabin 1—suggestive of iVDPV
Initially thought to arise from an immunocompromised healthcare source
Subsequent data suggest circulation in the community prior to index case’s infection
Serial stool cultures positive for polio until after successful BMT

15. Laboratory Findings 3/3 siblings
All anti-PV1 +, negative anti-PV2, anti PV3
Stool cultures negative
4 well children ages 2-14 yrs in 2 households shedding virus
Minimal contact with index household
30 HCWs and 35 patients culture negative at Hospital 4

16. Index Family

17. Epidemiological Findings
No known immunodeficient persons in MN Amish communities
No immunodeficient persons on staff of hospitals
No international immunodeficient persons of appropriate age in medical facilities in MN
No international VAPP in Shriner’s hospitals

18. Epidemiological Findings
No Amish with GBS/polio
No Amish with aseptic meningitis
9 cases of GBS in 3 years in 4 Amish counties
All 4 GBS in 2005 > 45 years
No illness compatible with polio in HCWs or patients at all 4 hospitals

19. Immunization Results
9 out of 24 families in index community accepted vaccination
31 out of 32 Amish families in nearby community which requested vaccination
9 out of 11 Amish families in another nearby community where vaccine was offered
Another nearby Amish community refused

20. Immunization Results Other MN Amish communities
35% to 100% initiated IPV
135 staff vaccinated Hospital 4

21. Conclusions
First identified VDPV in the US and first occurrence of VDPV transmission in a community since OPV discontinued in 2000
29th known chronically infected immunodeficient poliovirus excreter
Origin unknown
Virus likely circulating for approximately 2 years

22. Conclusions
Laboratory evidence polio virus circulated in the community
Index case likely infected in community
No evidence of circulation beyond MN Amish

23. Public Health Implications
Risk for transmission to communities with low vaccination coverage is high
Contacts between persons in communities with low vaccination coverage pose the potential for transmission to other communities in the US, Canada, and other countries
Last Polio Outbreak in the US occurred in 1979 among Amish

24. Public Health Implications
Prevalence of chronic VDPV infection unknown
iVPDV transmitted person-to-person
Implications for global eradication strategies