EPI vaccines-induced antibody prevalence in 8-9 year-olds in The Gambia.
OBJECTIVE
We evaluated antibody prevalence to measles, polio 1 and 3, and tetanus toxoid antibodies in 8-9 year-old children in The Gambia within the framework of the Gambia Hepatitis Intervention Study (GHIS), a large vaccine trial aimed at evaluating vaccine efficacy against hepatitis B virus (HBV) infection, chronic carriage and primary liver cancer in a high risk population. The results of the present survey were compared with a previous survey performed with the same objectives and same methodology but in different children at 3-4 years of age.


METHODS
Four clusters of 200 children each were sampled as representative of the whole country. Children would have received BCG, diphtheria-pertussis-tetanus vaccine (DPT), poliovirus vaccine (OPV), measles and yellow fever immunization. The measles haemoagglutination inhibition test (HAI) was used to detect measles antibody. Antibodies to polioviruses 1 and 3 were tested using the standard polio neutralization assay described in the EPI manual (WHO 1990). An enzyme-linked immuno-sorbent assay (ELISA) was used to measure tetanus toxoid antibodies.


RESULTS
A high proportion of children were fully vaccinated in both age groups. Measles antibody concentrations were < or =1 : 8 in 8.2% of 8-9 year-old vaccinated children. In the previous survey of 3-4 year-old children this was 11.3%. In the present survey, GMC was lower than in the 3-4 year-old children; 88% of 3-4 year-olds and 89% of 8-9 year-olds had detectable antibody levels against poliovirus type 1. Fewer children at 8-9 years of age had antibodies against poliovirus type 3 than 3-4 year-olds (78%vs. 89% P < 0.001). A significant overall lower proportion of 8-9 year-old children had detectable tetanus toxoid antibodies compared to 3-4 year-old children (87%vs. 95% P < 0.001), as well as those who received four doses of DPT (90%vs. 97% P < 0.001). Conclusions High vaccine coverage is achieved in The Gambia with EPI. With time the number of vaccinated children who are not protected against measles, poliovirus 3 and tetanus increases. Besides the maintenance of high vaccine coverage in infants and young children, booster doses of some of the EPI vaccines in adolescents should be considered.
Viviani
Simonetta
S
Gambia Hepatitis Intervention Study, International Agency for Research on Cancer (WHO), Lyon, France. sviviani@hotmail.com
Mendy
Maimuna
M
Jack
Abdoulie D
AD
Hall
Andrew J
AJ
Montesano
Ruggero
R
Whittle
Hilton C
HC
D000907:Antibodies, Bacterial / Q000097:blood*; D000914:Antibodies, Viral / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D003906:Developing Countries; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000276:immunology; D005714:Gambia; D006801:Humans; D017589:Immunization Programs; D007115:Immunization Schedule; D008458:Measles Vaccine / Q000276:immunology; D008459:Measles virus / Q000276:immunology; D017955:Poliovirus / Q000276:immunology; D014611:Vaccination / Q000706:statistics & numerical data
D000907:Antibodies, Bacterial; D000914:Antibodies, Viral; D015721:Diphtheria-Tetanus-Pertussis Vaccine; D008458:Measles Vaccine