VAPP in Immunodeficient Children, Iran | CDC EID

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Volume 16, Number 7–July 2010
Dispatch
Vaccine-associated Paralytic Poliomyelitis in Immunodeficient Children, Iran, 1995–2008
Shohreh Shahmahmoodi, Setareh Mamishi, Asghar Aghamohammadi, Nessa Aghazadeh, Hamideh Tabatabaie, Mohammad Mehdi Gooya, Seyed Mohsen Zahraei, Taha Mousavi, Maryam Yousefi, Kobra Farrokhi, Masoud Mohammadpour, Mahmoud Reza Ashrafi, Rakhshandeh Nategh, and Nima Parvaneh
Author affiliations: Tehran University of Medical Sciences, Tehran, Iran (S. Shahmahmoodi, S. Mamishi, A. Aghamohammadi, N. Aghazadeh, H. Tabatabaie, M. Yousefi, K. Farrokhi, M. Mohammadpour, R. Nategh, N. Parvaneh); Ministry of Health Center for Disease Control and Management, Tehran (M.M. Gooya, S.M. Zahraei, T. Mousavi); and Pediatrics Center of Excellence, Tehran (S. Mamishi, A. Aghamohammadi, M. Mohammadpour, M.R. Ashrafi, N. Parvaneh)

Suggested citation for this article

Abstract
To determine the prevalence of vaccine-associated paralytic poliomyelitis (VAPP) in immunodeficient infants, we reviewed all documented cases caused by immunodeficiency-associated vaccine-derived polioviruses in Iran from 1995 through 2008. Changing to an inactivated polio vaccine vaccination schedule and introduction of screening of neonates for immunodeficiencies could reduce the risk for VAPP infection.
After establishment of the Global Polio Eradication Initiative in 1988, the incidence of polio worldwide decreased from ≈350,000 cases annually to 1,606 cases in 2009 (1). Oral polio vaccine (OPV) has been efficiently used for >40 years and is associated with few adverse events (2). Its most commonly recognized adverse event, vaccine-associated paralytic poliomyelitis (VAPP), is estimated by the World Health Organization to cause 1 case per million births and by Minor (3) to cause ≈1 case per 6.2 million doses of OPV distributed.

VAPP is clinically indistinguishable from paralytic poliomyelitis caused by wild-type polioviruses (2) and occurs among healthy OPV recipients and their contacts, with onset temporally linked (within 60 days) to OPV exposure. Persons with primary immunodeficiencies are at >3,000-fold higher risk for VAPP (2,4). Isolates from immunodeficient VAPP (iVAPP) patients and some asymptomatic carriers show evidence of prolonged replication as indicated by >1% nucleotide sequence divergence from the corresponding Sabin OPV strain; such vaccine-derived polioviruses (VDPVs) isolated from immunodeficient persons after exposure to OPV are called iVDPVs (6,7).

Although most mutations involved in reversion of the OPV to a wild-type strain are found in the 5´ untranslated region of the virus genome, mutations have also been found in viral protein (VP) 1, VP2, and VP3 nt sequences (5). The >1% demarcation arises from the average rate of VP1 nt divergence of ≈1% per year, suggestive of prolonged replication (6,7). However, poliovirus evolution rates are variable, especially in the early phases of OPV replication (2). Immunodeficient OPV vaccine recipients are potential reservoirs for neurovirulent polio virus reintroduction into the population (8). To date, >44 cases in patients with immunodeficiency have been confirmed worldwide that excreted iVDPV for long periods (9,10). Timely diagnosis and containment of VDPVs needs to be addressed in posteradication strategies in regions where OPV is still used routinely. We present all 6 documented cases of iVAPP caused by iVDPVs diagnosed in Iran during 1995–2008 (Tables 1 and 2).

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Suggested Citation for this Article
Shahmahmoodi S, Mamishi S, Aghamohammadi A, Aghazadeh N, Tabatabaie H, Goya MM, et al. Vaccine-associated paralytic poliomyelitis in immunodeficient children, Iran, 1995–2008. Emerg Infect Dis [serial on the Internet]. 2010 Jul [date cited]. http://www.cdc.gov/EID/content/16/7/1133.htm

DOI: 10.3201/eid1607.091606