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Seroresponse to trivalent oral poliovirus vaccine as a function of dosage interval
A Cohen-Abbo1, B S Culley, G W Reed
1Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN 37232-2581, USA.
Insights
Successful immunization with trivalent oral poliovirus vaccine (TOPV) requires understanding key variables. This study found that while dose interval impacts early seroresponse, three doses before six months generally ensure immunity, unlike in developing nations.
Area of Science:
- Immunology
- Vaccinology
- Public Health
Background:
- Global polio eradication efforts depend on uniform vaccine efficacy.
- Seroresponses to trivalent oral poliovirus vaccine (TOPV) vary significantly worldwide.
- Dosage interval is a potential variable influencing TOPV immunization success.
Purpose of the Study:
- To investigate the effect of different dosage intervals on infant seroresponses to TOPV.
- To compare the immunogenicity of TOPV administered at 2, 3, 4 months versus 2, 4, 6 months of age.
Main Methods:
- A clinical trial involving 108 infants.
- Random assignment to two TOPV dosing schedules: 2, 3, 4 months or 2, 4, 6 months.
- Assessing seroresponse rates to each poliovirus type after three vaccine doses.
Main Results:
- Virtually complete immunity for all three poliovirus types was achieved in both groups after three TOPV doses before six months of age.
- A trend towards lower seroresponse rates with the shorter (2, 3, 4 months) dose interval after two doses was observed, though not statistically significant (P=0.15).
- Significant differences in TOPV response compared to developing countries, where multiple doses may not ensure protection, were noted.
Conclusions:
- Three doses of TOPV administered before six months of age generally elicit a strong immune response in infants.
- While shorter intervals may slightly reduce early seroresponse, they do not preclude effective immunity with a full primary series.
- Factors beyond dosage interval are critical in explaining lower TOPV efficacy observed in developing countries.
Abstract:
Seroresponses to trivalent oral poliovirus vaccine are not uniform throughout the world. Definition of the variables that determine successful immunization is vital to ensure global polio eradication. One such variable may be dosage interval. To investigate this effect 108 infants were enrolled in a clinical trial and randomly assigned to receive three doses of trivalent oral poliovirus vaccine (standard United States formulation) at 2, 3 and 4 or 2, 4 and 6 months of age. After three doses of vaccine given before 6 months of age, immunity was virtually complete for each of the three poliovirus types in both groups. After two doses the seroresponse rate to each type was less with the shorter dose interval. However the difference was not significant (P = 0.15) in the sample size studied. Such responses differ markedly from those seen in developing countries, where four or more doses of vaccine may fail to provide complete protection. Differences other than dosage interval must contribute to those failures.