Low-dose hepatitis B vaccine immunisation in children

Hepatitis B immunisation in persons not previously exposed to hepatitis B or with unknown exposure status

BACKGROUND

The benefits and harms of hepatitis B vaccination in persons not previously exposed to hepatitis B infection or with unknown exposure status have not been established.

OBJECTIVES

To assess the benefits and harms of hepatitis B vaccination in people not previously exposed to hepatitis B infection or with unknown exposure status.

SEARCH STRATEGY

Trials were identified from The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, LILACS,Science Citation Index Expanded (last search, March 2007). Additionally, we contacted experts and vaccine manufacturers, and read through reference lists for eligible trials.

SELECTION CRITERIA

Randomised clinical trials comparing hepatitis B vaccine versus placebo, no intervention, or another vaccine in persons not previously exposed to hepatitis B (HBsAg negative) or with unknown exposure status.

DATA COLLECTION AND ANALYSIS

The primary outcome was hepatitis B infection (detecting HBsAg, HBeAg, HBV DNA, or anti-HBc). Secondary outcomes were lack of sero-protection, antibody titre, clinical complications, adverse events, lack of compliance, and cost-effectiveness. Dichotomous outcomes were reported as relative risk (RR) with 95% confidence interval (CI), using intention-to-treat analysis assuming an unfavourable event for missing data. Sensitivity analyses based on methodological quality (risk of bias), available data analysis, intention-to-treat analysis assuming a favourable event for missing data, best-case scenario, and worst-case scenario were conducted.

MAIN RESULTS

Twelve trials were eligible. All had high risk of bias and reporting was inconsistent. Hepatitis B vaccine did not show a clear effect on the risk of developing HBsAg (RR 0.96, 95% CI 0.89 to 1.03, 4 trials, 1230 participants) and anti-HBc (RR 0.81, 95% CI 0.61 to 1.07; 4 trials, 1230 participants, random-effects) when data were analysed using intention-to-treat analysis assuming an unfavourable event for missing data. Analysis based on data of available participants showed reduced risk of developing HBsAg (RR 0.12, 95% CI 0.03 to 0.44, 4 trials, 576 participants) and anti-HBc (RR 0.36, 95% CI 0.17 to 0.76, 4 trials, 576 participants, random-effects). Intention-to-treat analysis assuming favourable outcome for missing data showed similar reduction in risk. Hepatitis B vaccination had an unclear effect on the risk of lacking protective antibody levels (RR 0.57, 95% CI 0.26 to 1.27, 3 trials, 1210 participants, random-effects). Development of adverse events was sparsely reported.

AUTHORS' CONCLUSIONS

In people not previously exposed to hepatitis B, vaccination has unclear effect on the risk of developing infection, as compared to no vaccination. The risk of lacking protective antibody levels as well as serious and non-serious adverse events appear comparable among recipients and non-recipients of hepatitis B vaccine.

Antibody response to preS1 in hepatitis-B-virus-induced liver disease and after immunization

Antibodies to the pre-S1-encoded sequence of hepatitis B virus (HBV) envelope were detected by ELISA using a synthetic peptide analogue of preS1 proteins, in different groups of HBV-infected subjects and also in hepatitis B vaccine recipients. Such antibodies were specifically found in only 1% of HBsAg chronic carriers including patients with cirrhosis and primary liver cancer. Anti-preS1 were detected in patients with acute hepatitis; in 13% of the HBsAg+ sera obtained before recovery and in 37% of the sera obtained after recovery. Anti-preS1 antibodies were detected in recipients of a plasma-derived vaccine, but not in those receiving a recombinant vaccine. The results indicate that anti-preS1 is an earlier serum marker of HBV clearance than anti-preS2 and anti-S antibodies.

Anti-pre-S2 antibodies in natural hepatitis B virus infection and after immunization

Anti-pre-S2 antibodies were detected by enzyme-linked immuno-absorbant assay using a synthetic peptide analogue of pre-S2 protein, in different groups of hepatitis-B-infected subjects, including patients presenting with cirrhosis and liver cancer, and also in infants immunized with hepatitis B vaccine. Anti-pre-S2 antibodies were not detected in hepatitis B surface antigen (HBsAg) chronic carriers, including patients with cirrhosis or primary liver cancer. Anti-pre-S2 antibodies were not detected in HBsAg-positive sera during the early phase of acute hepatitis. They were only noted upon recovery, when anti-HBs antibodies are detectable at the same time as HBsAg. After recovery, anti-pre-S2 antibodies were noted in 57% of test sera and were still detectable in 16% of anti-HBs-positive sera obtained years after HBV infection. Anti-pre-S2 antibodies were detected in 70% of infants immunized with 2 or 5 micrograms doses of Hevac B Pasteur vaccine, confirming that this vaccine contains pre-S2 antigen. Anti-pre-S2 detection was correlated with the anti-HBs antibody titre.

HBsAG positive reactivity in man not due to hepatitis B virus

A viral infection characterised by serum HBsAg positivity with serum anti-HBc negativity has been encountered in Senegal. The infection is not associated with the presence of HBeAg, so it differs from hepatitis B virus in its core antigen, but the surface antigen of the two viruses share some epitopes. After the loss of HBsAg, neither anti-HBc nor anti-HBs becomes detectable. Anti-HBs, naturally acquired or produced by immunisation, does not protect against this new infection. Chronic carriage occurs. If this new infection is confirmed to cause chronic liver disease, hepatitis B vaccine should include surface antigen from the new virus.