Transversal sero-epidemiological study of Bordetella pertussis in Tehran, Iran

Abstract

Objectives Pertussis remains endemic despite high vaccine coverage in infants and toddlers. Pertussis vaccines confer protection but immunity wanes overtime and boosters are needed in a lifetime. Iran, eligible for the Expanded Program on Immunization that includes the primary immunization, implemented two additional booster doses using a whole-cell vaccine (wPV) at 18 months-old and about 6 years-old. Duration of protection induced by the wPVs currently in use and their impact as preschool booster are not well documented. This study aimed at assessing vaccination compliance and at estimating the duration of protection conferred by vaccination with wPV in children aged < 15 years in Tehran, Iran. Methods Detailed information on vaccination history and capillary blood samples were obtained from 1047 children aged 3-15 years who completed the 3 doses-primary pertussis immunization, in Tehran. Anti-pertussis toxin IgG levels were quantified by ELISA. Results Compliance was very high with 93.3% of children who received the three primary and 1 st booster doses in a timely manner. Timeliness of the 2 nd booster was lower (63.3%). Rate of seropositive samples continuously and significantly increased from 1-2 to 5-6 years after 1 st booster attaining 30.4% of children exhibiting serological sign of recent contact with B. pertussis. Second booster dating back 1 or 2 years was associated with high antibody titers, which significantly decreased within 3 years from injection. Among children who received 2 nd booster injection more than 2 years before serum analysis, seroprevalence of pertussis infection was 8.4% and seropositivity rate was higher from the 10 years-old group.

Hospital-based prospective study of pertussis in infants and close contacts in Tehran, Iran

“…Only 4 infants were late in starting the vaccination program among the 199 participating infants, and > 90% of those infants who were vaccinated complied with the national vaccination schedule in this study. Compliance with vaccination schedule was also found to be very good among vaccinated children 3–15 years old in Tehran, confirming our data [ 10 ]. Timeliness may nevertheless vary throughout the country as high incidence of delayed vaccination was reported in the outskirt of Iran’s big cities [ 23 ].…”

“…This relationship with infant and age distribution of primary case contacts was recently shown to be similar in HIC where aPVs are used [ 24 ]. The important rate of pertussis infection among contact cases observed herein highlights the underreporting among older children and adults and are in line with studies evidencing substantial circulation of pertussis among Iranian children and adolescents [ 10 , 25 ]. In addition, although all positive children presented symptoms, more than 30% of older individuals did not recall having or did not have cough at any time during the study.…”

“…Timeliness of primary vaccination schedule in infants was analyzed based on the national recommendations. Definition used was the following: having received the 1st dose at 2 months +/− 14 days, and the 2nd and 3rd doses at 4 to 10 weeks interval from the previous dose [ 10 ].…”

Bordetella pertussis in School-Age Children, Adolescents, and Adults: A Systematic Review of Epidemiology, Burden, and Mortality in the Middle East

“…A recent serosurvey study that was published after the review search period assessed children and adolescents aged 3-15 years in Tehran between December 2016 and February 2017. The seroprevalence of anti-PT IgG showed that B. pertussis was circulating, despite high coverage of childhood pertussis vaccination and the pre-school booster [61]. Among serum samples from 1010 children and adolescents, the seropositivity rate (PT IgG [ 40 IU/ml) was significantly higher among children who received their first booster dose 5-6 years previous to the study compared with those who had received it within 1-2 years (30.4% versus 2.4%, respectively).…”

“…In children who had received the second booster dose, seropositivity rates in children receiving it within 1 years and 1-2 years were 27.7% and 32.5%, respectively, and rates were significantly lower in children receiving it within 2-3 years (11.1%). The authors suggest that vaccine-acquired immunity after the first booster dose at 18 months had waned within about 2 years and that a second booster dose in children aged 5-6 years improves longer term antibody persistence [61].…”