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Poliovirus neutralising antibody in infants and cord blood
M Yin-Murphy1, K L Tan, G N Lim
1Department of Neonatology, National University of Singapore.
Insights
Singapore
Area of Science:
- Immunology
- Vaccinology
- Public Health
Background:
- Singapore's participation in the WHO Expanded Programme on Immunization (EPI) protocol.
- Concerns regarding serological response to oral poliovirus vaccine (OPV) in infants.
- Maternal antibody transfer's limited protective role against poliomyelitis.
Purpose of the Study:
- To assess the serological response and seroconversion rates to Trivalent Oral Poliovirus Vaccine (TOPV) in Singaporean infants.
- To evaluate the reliability of passively transferred maternal antibodies for infant protection.
- To highlight the critical need for vaccine potency testing and ongoing surveillance for wild polioviruses.
Main Methods:
- Rapid assessment of serological response using WHO EPI protocol.
- Analysis of seropositivity in infants under one year old.
- Investigation of poliovirus neutralizing antibodies in cord blood samples.
Main Results:
- 100% seropositivity in infants was observed, but this does not confirm seroconversion to TOPV.
- Maternal antibodies in cord blood offer insufficient protection against poliomyelitis.
- Isolation of non-Sabin-like polioviruses from imported cases and unexpectedly from Singaporean citizens.
Conclusions:
- Routine infant serological response data alone is insufficient to guarantee vaccine efficacy.
- Vaccine potency testing is crucial for maintaining effective polio immunization programs.
- Continuous surveillance for wild polioviruses is essential, even in polio-free regions, due to imported cases and potential environmental circulation.
Abstract:
Singapore participated in the WHO EPI protocol for rapid assessment of serological response to three doses of standard oral poliovirus vaccine. The 100% seropositive finding of thirty infants below one year old is no proof of seroconversion rate to the Trivalent Oral Poliovirus Vaccine (TOPV) administered. Investigation of 100 cord blood samples showed that passively transferred maternal poliovirus neutralising antibody cannot be relied upon for protection of infants against poliomyelitis. This paper emphasises the importance of vaccine potency testing and serves as a timely reminder that although the last case of indigenous poliomyelitis was recorded in 1974, non Sabin-like (wild) polioviruses are being isolated from imported cases and foreigners hospitalised in Singapore, and unexpectedly, from the conjunctiva and pharynx of Singaporeans treated for conjunctivitis. It discusses the WHO (World Health Organization) Plan of Action for Eradication of Polio in the Western Pacific Region which includes Singapore.