Seroprevalence of Bordetella pertussis specific Immunoglobulin G antibody levels among asymptomatic individuals aged 4 to 24 years: a descriptive cross sectional study from Sri Lanka

Abstract

BackgroundIn Sri Lanka pertussis continues to circulate in the community and cases among adolescents and adults have been reported despite 95% coverage of the four dose pertussis vaccination during early childhood. Waning of immunity following natural infection or immunization may contribute to the persistent circulation. An adolescent booster dose is not included in the national immunization schedule of Sri Lanka, although this is routine practice in many countries. Therefore information on immunity to pertussis in the adolescent group is needed prior to considering vaccination schedule changes.MethodsThe quantitative determination of specific Immunoglobulin G antibodies to Bordetella pertussis toxin was done using a commercially available validated ELISA method. The antibody values were categorized into groups according to the interpretive criteria provided by the manufacturer. The values were <55 IU/mL, negative; 55–<60 IU/mL, borderline; 60–125 IU/mL, positive; >125, strongly positive respectively. Sera of 385 asymptomatic individuals aged 4 to 24 years admitted to surgical units of Lady Ridgeway Hospital, Colombo and Colombo South Teaching Hospital were used for the study. Mann-Whitney U and Kruskal-Wallis tests were used in analysis of results and p ≤0.05 was considered as statistically significant. Details of epidemiological variables were collected using a questionnaire and correlation with significant levels of pertussis antibodies was determined.ResultsMedian age of the study population was 12 years with 212 (55.1%) females. The median anti PT antibody level was 3.31 IU/mL and 352 (91%) had anti PT levels ≤55 IU/mL. Median of anti PT levels were 3.18 IU/mL for 4–7 years, 1.43 IU/mL (IQR 0.336–6.27) for 8–11 years, 4.28 IU/mL (IQR 0.978–13.39) for 12–15 years, 6.14 IU/mL for 16–19 years and 4.89 IU/mL for 20–24 years and the differences were statistically significant (p = 0.000). Females (p < 0.003) and those having a sibling aged ≥12 years (p = 0.017) had significantly higher anti PT levels.ConclusionsThe majority of the study population, especially 8 to 11 year age group had low anti PT IgG levels. The higher antibody titers in the 12–15 year age group seem to indicate infection in early adolescence. A booster dose of acellular pertussis vaccine need to be considered.

Is it time to administer acellular pertussis vaccine to childbearing age/pregnant women in all areas using whole-cell pertussis vaccination schedule?

“…The studied cases were from different age groups while we studied only childbearing age women. [28][29][30][31] However, all evaluated studies recommended a Tdap booster dose when the waning of vaccine-elicited immunity supported the need for a booster dose at that age.…”

“…29 A booster dose of acellular pertussis vaccine was also suggested to be considered by Sigera et al in Sri Lanka. 30 Sera of 385 asymptomatic individuals aged 4-24 years were used for this study. The majority of the study population, especially the 8-11 years age group had low anti-pertussis toxin IgG levels.…”

Seroprevalence of pertussis in adult population

“…It is unclear whether there is a true link between pertussis and sex. However, pertussis is considered more common among females globally, and whether this is due to higher immunogenicity of the female population or higher exposure to disease is yet to be defined [23,24,25].…”

Clinical Experiences in Pertussis in a Population with High Vaccination Rate

“…The duration of immunity of the wP vaccine is 4-12 years, and the aP protection begins to diminish after 4-5 years. This led to the need of a booster dose in the adolescence (from 8 to 11 years), because adolescents present low levels of antibodies, which increase later in life (from 12 to 15 years) due to natural infection [44].…”

“…Health professionals in contact with pregnant women, parturients, newborns, and young infants should also be prioritized. New studies are needed to assess the real impact of this measure [16,44,62].…”