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J Infect Dis. 2019 Mar 14. pii: jiz124. doi: 10.1093/infdis/jiz124. [Epub ahead of print]

Rapid Disappearance of Poliovirus Type 2 Immunity in Young Children Following Withdrawal of Oral Poliovirus Type 2 Containing Vaccine in Vietnam.

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National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
Polio Eradication Department, World Health Organization, Geneva, Switzerland.
Pasteur Institute, Ho Chi Minh city, Vietnam.
Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.



Due to global shortage of inactivated poliovirus vaccine and global withdrawal of poliovirus type-2 (PV2) containing oral vaccine in May 2016, Vietnam has not used any PV2-containing vaccine between May 2016-October 2018. We assessed population immunity gap to PV2.


A cross-sectional survey in children 1-18 months of age was carried out in January 2018: one blood sample was obtained and analysed for the presence of poliovirus neutralizing antibodies. In children with detectable anti-PV2 antibodies, a second blood sample was obtained and analysed four months later to distinguish between passive (maternally-derived) and active (induced by secondary transmission or vaccination) immunity.


Analysable sera were obtained from 1,106/1,110 enrolled children. Seroprevalence of PV2 antibodies was 87/368 (23.6%) among 1-7-month-old; 27/471 (5.7%) in the 8-15-month-old; and 19/267 (7.1%) in the 16-18-month-old. Seroprevalence declined with age in the 1-7 month-old group, and in children 8-18 months it remained without significant change by age. Four months later, 11/87 (14%), 9/27 (32%), and 12/19 (37%) remained seropositive in the 1-7, 8-15, and 16-18-month groups, respectively.


We found declining immunity to PV2, suggesting that Vietnam is at risk for an outbreak of type 2 vaccine-derived poliovirus in case of importation or new emergence.


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