How is immunity to polio (Poliomyelitis) and pertussis (Pertussis) typically tested and confirmed?

Testing for Polio and Pertussis Immunity

For both polio and pertussis, laboratory testing is essential for confirming immunity, with serologic testing being the primary method for immunity assessment rather than diagnostic testing for active disease.

Polio Immunity Testing

Serologic Testing

• The gold standard for assessing polio immunity is testing for neutralizing antibodies against the three poliovirus serotypes (types 1,2, and 3) 1, 2
• Neutralizing antibody tests are the only CDC-endorsed method for determining immunity to poliovirus 1
• A protective level of antibody indicates immunity against poliomyelitis 1

Testing Procedure

• Serum specimens are collected and tested for neutralizing antibody to each of the three poliovirus serotypes 1
• The standard protocol for poliovirus serology should be used as recommended by the CDC 1
• Commercial laboratories may perform complement fixation and other tests, but these are difficult to interpret due to inadequate standardization and relative insensitivity 1

Interpretation of Results

• A fourfold rise in antibody titer between acute-phase and convalescent-phase serum specimens is diagnostic for poliovirus infection, not immunity 1
• For immunity assessment, a single serum sample showing protective antibody levels is sufficient 1, 2
• The CDC Enterovirus Laboratory is available for consultation and testing of specimens 1

Pertussis Immunity Testing

Serologic Testing

• Pertussis immunity is typically assessed through serologic testing for antibodies against pertussis antigens 1, 3
• Diagnosis of pertussis infection by serology generally requires demonstration of a substantial change in titer (usually fourfold) when comparing results from acute and convalescent sera 1
• Single sample serologic assays for pertussis immunity lack standardization in most settings 1

Testing Considerations

• Massachusetts uses a single sample serologic assay with age-specific antibody reference values as a diagnostic test for adolescents and adults, but this is not available elsewhere 1
• Most single sample serologic assays cannot clearly differentiate immune responses to pertussis antigens following recent disease, from more remote disease, or from vaccination 1
• None of these serologic assays, including the Massachusetts assay, is licensed by FDA for routine diagnostic use in the United States 1

Interpretation of Results

• After receiving the 5-dose DTaP series, protection against pertussis reaches its peak at 98.1% effectiveness within the first year 4
• Protection wanes over time, with effectiveness declining to approximately 71.2% by ≥5 years after the fifth dose 4
• A considerable drop in pertussis antibody levels may be observed about 3-5 years after booster vaccination 5

Clinical Implications and Considerations

Polio

• In the United States, IPV (inactivated poliovirus vaccine) is the only recommended vaccine for prevention of poliomyelitis 1
• After a complete vaccination series, most individuals develop protective levels of antibodies against all three poliovirus serotypes 1, 6
• Preterm infants can achieve protective antibody levels similar to term infants after vaccination 6

Pertussis

• Pertussis immunity wanes more rapidly than tetanus or diphtheria immunity 4
• After 3 doses of DTaP, vaccine efficacy estimates range from 79% to 89% against culture-confirmed pertussis disease 4
• The complete 5-dose DTaP series has an estimated overall effectiveness of 88.7% 4
• Booster doses are required to maintain immunity against pertussis 4

Common Pitfalls and Caveats

• For pertussis, the CDC does not endorse serologic testing for routine diagnostic use due to lack of standardization 1, 3
• For polio, assays other than neutralization tests (such as complement fixation) should be interpreted with caution due to inadequate standardization 1
• When assessing immunity in individuals vaccinated outside the United States, different vaccination schedules may need to be considered 1
• Dried blood spot cards have been proposed as an alternative medium for sample collection to enhance surveillance of poliovirus immunity 2