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Antibody Response to Pertussis Vaccine Among Children and Adolescents in Croatia: A Cross-Sectional Prevalence Study
Vedran Stevanović1,2, Oktavija Đaković Rode2,3, Goran Tešović1,4
1Pediatric Infectious Diseases Department, University Hospital for Infectious Diseases "Dr. Fran Mihaljević", Mirogojska 8, 10000 Zagreb, Croatia.
Insights
Pertussis immunity wanes in vaccinated Croatian children, with low antibody levels observed. Protection may persist for 8-9 years, suggesting ongoing pertussis circulation and potential need for booster vaccines.
Area of Science:
- Immunology
- Vaccinology
- Public Health
Background:
- The national vaccination program in Croatia has not fully controlled *Bordetella pertussis* transmission.
- Pertussis vaccine-induced immunity duration is a concern, especially with shifts in vaccine formulations.
Purpose of the Study:
- To measure IgG antibodies to pertussis toxin (IgG-anti-PT) in vaccinated Croatian children aged 6-18.
- To estimate the longevity of immunity from the National Immunization Program (NIP).
Main Methods:
- A cross-sectional seroprevalence study analyzed 1314 serum samples from 2020-2023.
- IgG-anti-PT concentrations were quantified using ELISA, with <40 IU/mL considered negative.
Main Results:
- The majority (95.1%) of subjects had IgG-anti-PT levels below 40 IU/mL.
- A low geometric mean concentration (GMC) of IgG-anti-PT was observed, indicating waning immunity.
- Waning IgG-anti-PT concentrations were evident across age groups.
Conclusions:
- Only 0.53% of participants were seropositive (>100 IU/mL).
- Despite low antibody levels, protection against pertussis may last 8-9 years.
- Ongoing *B. pertussis* circulation is suggested, and booster pertussis vaccines for adolescents warrant further investigation.
Background/Objectives:
The current national vaccination program does not completely control the transmission of Bordetella pertussis in Croatia. This cross-sectional seroprevalence study aimed to measure the prevalence of IgG antibodies to pertussis toxin (IgG-anti-PT) in regularly vaccinated Croatian children of 6-18 years of age and to estimate the duration of pertussis vaccine-induced immunity elicited by the National Immunization Program (NIP) with respect to the transition from a mixed acellular pertussis (DTaP) and whole-cell pertussis (DTwP) vaccine regimen to a DTaP regimen.
Materials And Methods:
Single-serum IgG-anti-PT concentrations were measured using a commercial enzyme-linked immunosorbent assay (ELISA) and analyzed in twelve age groups from 2020 to 2023. According to the manufacturer's classification, IgG-anti-PT concentrations of <40 IU/mL, 40-100 IU/mL, and >100 IU/mL were considered negative, borderline, and positive, respectively.
Results:
In total, 1314 sera samples were collected and analyzed. Most subjects had an IgG-anti-PT concentration < 40 IU/mL (95.1%). This study sample's IgG-anti-PT geometric mean concentration (GMC) was very low. Despite different vaccination backgrounds, the waning of IgG-anti-PT concentration was observed in Croatian children and adolescents.
Discussion:
In the present study, 0.53% of subjects were seropositive (>100 IU/mL). Regardless of the low quantity of IgG-anti-PT, we estimated that a degree of protection against pertussis persisted for at least 8-9 years based on a small increase in IgG-anti-PT GMC in 15-18-year-olds, indicative of an ongoing B. pertussis circulation in Croatia. Although introducing a booster pertussis vaccine could be suitable for young adolescents to strengthen their immunity, before such a recommendation, it would be useful to initiate further research to complement the results obtained in this study.
