Seroimmunity to Pertussis among Egyptian Neonates and Their Mothers and Infants

Abstract

Despite decades of high vaccination coverage, pertussis has remained endemic and re-emerged as a public health problem in many countries in the past 2 decades. The recent emergence of whooping cough in other parts of the world and the concern of its re-emergence in Egypt have stimulated us to evaluate the current state of seroimmunity against pertussis in a group of healthy Egyptian neonates and their mothers and infants in relation to the mothers and infants vaccination profile. This cross-sectional study included 250 healthy individuals that are stratified as 75 healthy neonates and their mothersand 100 healthy infants up to the age of 2 years. They were enrolled consecutively from the Department of Gynaecology and Obstetrics, Ain Shams University and from the Outpatient PediatricClinic in theChildren's hospital, Ain Shams University and the Primary Health Care Unit of the Ministry of Health in Obour city. Both groupswere subjected to clinical evaluation and estimation of serum pertussis specific IgG was estimated by the enzyme linked immunosorbent assay. Positive titer of serum pertussis IgG was detected in 92% of the studied mothers and 84% of their newborns. Among the studied infants, 55% were immune against pertussis.Mothers living in urban and suburban areas had significantly higher serum pertussis IgG level than those living in rural areas. Infants aged 12 to 24 months had significantly higher pertussis IgG titers as compared to infants less than 6 months but comparable to those aged 6 to 12 months. No difference in the pertussis sero-immunity rates or antibody titre was observed between males and females in the studied groups. The persistence of acceptable pertussis seroimmunity rates and antibody titres in the mothers could be due to the use of whole cell vaccine included in the national EPI schedule augmented by subclinical exposure to natural infection. The seroconversionfailure rates detected in infants could be due to inefficient vaccination and may suggest the need for a booster vaccine dose. The lower seroimmunity observed among rural residents might reflect difference in adherence to vaccination programs and the need for ensuring compliance among these groups. Wider scale studies would allow better insight into the Egyptian status and hence the possible need for booster immunization.