Cancer in the Gambia: 1988-97.

We describe the incidence of cancer in The Gambia over a 10-year period using data collected through the Gambian National Cancer Registry. Major problems involved with cancer registration in a developing country, specifically in Africa are discussed. The data accumulated show a low overall rate of cancer incidence compared to more developed parts of the world. The overall age standardized incidence rates (ASR) were 61.0 and 55.7 per 100 000 for males and females, respectively. In males, liver cancer was most frequent, comprising 58% of cases (ASR 35.7) followed by non-Hodgkin lymphoma, 5.4% (ASR 2.4), lung 4.0%, (ASR 2.8) and prostate 3.3% (ASR 2.5) cancers. The most frequent cancers in females were cervix uteri 34.0% (ASR 18.9), liver 19.4% (ASR 11.2), breast 9.2% (ASR 5.5) and ovary 3.2% (ASR 1.6). The data indicate that cancers of the liver and cervix are the most prevalent cancers, and are likely to be due to infectious agents. It is hoped that immunization of children under 1 year against hepatitis B will drastically reduce the incidence of liver cancer in The Gambia.

Hepatitis B virus DNA in relation to duration of hepatitis B surface antigen carriage.

This study determined the prevalence and concentration of hepatitis B virus (HBV) DNA in chronic carriers of hepatitis B surface antigen (HBsAg) in The Gambia, West Africa. Ninety-nine young child carriers aged three to four years, 115 older child carriers aged five to 14 years, 71 adult carriers and 105 infected children who were not carriers were included. Detection of HBV DNA was performed by dot blot hybridisation using a radioactive phosphorus (32P) method and by non-radioactive enhanced chemiluminescence (ECL). Chromoscan-3 equipment was used to quantify DNA, and ECL and the 32P method were compared. Sensitivity and specificity of ECL were 95.8% and 100% respectively, with a detection limit of 0.3 pg/microL (0.3 x 10(5) genomic copies) compared to 0.15 pg/microL (0.15 x 10(5) genomic copies) for the 32P-labelled probe. The prevalence of HBV DNA was 74% (74/99) in young carriers, 30% (35/115) in older child carriers and 12.6% (9/71) in adult carriers. The geometric mean (GM) values for HBV DNA were significantly different between age groups (P = 0.031) and HBV DNA, which declined significantly with age (r = 0.16, P < 0.001 for log32P values), ranged from 1.48 pg/microL in young carriers to 0.29 pg/microL in adults over 24 years. The GM value of HBV DNA was related to duration of carriage. Higher values were found in young carriers known to be HBsAg-positive for less than three years compared with adult carriers of at least 20 years' duration. The GM (95% confidence limit [CL]) values were 1.48 pg/microL (1.42, 1.53) and 0.29 pg/microL (0.25, 0.33) respectively. The level of HBV DNA in hepatitis B envelope antigen (HBeAg)-positive carriers was higher than in HBeAg-negative carriers, the GM (95% CL) being 1.23 pg/microL (1.19, 1.27) and 0.34 pg/microL (0.25, 0.42) respectively.

What level of hepatitis B antibody is protective?

This study assessed the level of vaccine-induced hepatitis B surface antibody that is protective against hepatitis B infection and carriage in The Gambia. Sera from 700 of a cohort of 1041 children vaccinated against hepatitis B in infancy were serially tested for markers of hepatitis B until age 7 years. No absolute level of protection against infection was found, but all children who attained a peak antibody response to vaccination of >=10 IU/L were protected against carriage of hepatitis B surface antigen. Two-thirds of 45 infected children experienced brief infection (determined by loss of core antibody). This transient infection was likely related to surface antibody level. The data support the use of the peak antibody response as the best indicator of protection against carriage and suggest that most infections after vaccination are short-lived.

Efficacy of hepatitis B vaccine in the Gambian expanded programme on immunisation.

Because of the high prevalence of hepatitis B virus (HBV) infection in The Gambia, HBV vaccination has been incorporated into the national expanded programme on immunisation. We have assessed the efficacy of the vaccine against HBV infection and chronic carriage by examining 720 3-4-year-old children who had received the vaccine in infancy and 816 who had not received it. The vaccine was 84% (95% CI 78-89%) effective against infection and 94% (84-98%) effective against chronic carriage. Vaccinated infants of mothers positive for hepatitis B surface and e antigens were at greater risk of breakthrough infection and chronic carriage than infants of uninfected mothers. The high vaccine efficacy against the HBV carrier state, the main risk factor for the development of chronic liver disease and liver cancer, offers hope that the prevalence of these diseases may be reduced in the future.

PIP: As part of the Gambia Hepatitis Intervention Study, hepatitis B antigens and antibodies were assayed in 720 3-4 year old children who had received 4 doses of 10 mcg plasma-derived hepatitis B vaccine in infancy, the findings were compared with 816 controls. The cross sectional study took place from September, 1990, to July, 1991. Study subjects were tested for hepatitis B core antigen (HBcAg), as well as antigens and antibodies to hepatitis surface, e, and core protein, and those testing positive were tested a year later for HBsAg to determine chronic carrier status. Children negative for core antibody and surface antigen were considered uninfected; those positive for core antibody were considered infected; those positive for surface antigen 2 times 6 months apart were considered carriers. 4.6% of the vaccinated children were infected, and 0.6% were chronic carriers. 3 of these carriers had infected or carrier mothers, and 1 had only received 1 dose of vaccine. In the controls, there were 29% judged infected by anti-HBc, including 13% who were also positive for HBsAg. 86% of these were considered chronic carriers when tested a year later. Thus the vaccine was estimated to be 84% effective against infection and 94% effective against chronic carriage. The current Gambian vaccine consists of 2.5 mcg recombinant hepatitis B vaccine.