Immunogenicity and reactogenicity of a combined hepatitis A and B vaccine in healthy Chilean subjects

Hepatitis A immunisation in persons not previously exposed to hepatitis A

This review is withdrawn because it is outdated. A new review is to be published by the end of 2019.

Hepatitis A immunisation in persons not previously exposed to hepatitis A

BACKGROUND

In many parts of the world, hepatitis A infection represents a significant cause of morbidity and socio-economic loss. Whilst hepatitis A vaccines have the potential to prevent disease, the degree of protection afforded against clinical outcomes and within different populations remains uncertain. There are two types of hepatitis A virus (HAV) vaccine, inactivated and live attenuated. It is important to determine the efficacy and safety for both vaccine types.

OBJECTIVES

To determine the clinical protective efficacy, sero-protective efficacy, and safety and harms of hepatitis A vaccination in persons not previously exposed to hepatitis A.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and China National Knowledge Infrastructure (CNKI) up to November 2011.

SELECTION CRITERIA

Randomised clinical trials comparing HAV vaccine with placebo, no intervention, or appropriate control vaccines in participants of all ages.

DATA COLLECTION AND ANALYSIS

Data extraction and risk of bias assessment were undertaken by two authors and verified by a third author. Where required, authors contacted investigators to obtain missing data. The primary outcome was the occurrence of clinically apparent hepatitis A (infectious hepatitis). The secondary outcomes were lack of sero-protective anti-HAV immunoglobulin G (IgG), and number and types of adverse events. Results were presented as relative risks (RR) with 95% confidence intervals (CI). Dichotomous outcomes were reported as risk ratio (RR) with 95% confidence interval (CI), using intention-to-treat analysis. We conducted assessment of risk of bias to evaluate the risk of systematic errors (bias) and trial sequential analyses to estimate the risk of random errors (the play of chance).

MAIN RESULTS

We included a total of 11 clinical studies, of which only three were considered to have low risk of bias; two were quasi-randomised studies in which we only addressed harms. Nine randomised trials with 732,380 participants addressed the primary outcome of clinically confirmed hepatitis A. Of these, four trials assessed the inactivated hepatitis A vaccine (41,690 participants) and five trials assessed the live attenuated hepatitis A vaccine (690,690 participants). In the three randomised trials with low risk of bias (all assessing inactivated vaccine), clinically apparent hepatitis A occurred in 9/20,684 (0.04%) versus 92/20,746 (0.44%) participants in the HAV vaccine and control groups respectively (RR 0.09, 95% CI 0.03 to 0.30). In all nine randomised trials, clinically apparent hepatitis A occurred in 31/375,726 (0.01%) versus 505/356,654 (0.18%) participants in the HAV vaccine and control groups respectively (RR 0.09, 95% CI 0.05 to 0.17). These results were supported by trial sequential analyses. Subgroup analyses confirmed the clinical effectiveness of both inactivated hepatitis A vaccines (RR 0.09, 95% CI 0.03 to 0.30) and live attenuated hepatitis A vaccines (RR 0.07, 95% CI 0.03 to 0.17) on clinically confirmed hepatitis A. Inactivated hepatitis A vaccines had a significant effect on reducing the lack of sero-protection (less than 20 mIU/L) (RR 0.01, 95% CI 0.00 to 0.03). No trial reported on a sero-protective threshold less than 10 mIU/L. The risk of both non-serious local and systemic adverse events was comparable to placebo for the inactivated HAV vaccines. There were insufficient data to draw conclusions on adverse events for the live attenuated HAV vaccine.

AUTHORS' CONCLUSIONS

Hepatitis A vaccines are effective for pre-exposure prophylaxis of hepatitis A in susceptible individuals. This review demonstrated significant protection for at least two years with the inactivated HAV vaccine and at least five years with the live attenuated HAV vaccine. There was evidence to support the safety of the inactivated hepatitis A vaccine. More high quality evidence is required to determine the safety of live attenuated vaccines.

Combined hepatitis A and B vaccines: a review of their immunogenicity and tolerability

Three combined hepatitis A and B vaccine preparations are commercially available in various countries: a two-dose paediatric formulation (Ambirix) [administered at months 0 and 6-12]; and a three-dose adult (Twinrix Adult) or paediatric (Twinrix Paediatric) formulation (administered at months 0, 1 and 6). The adult vaccine provides consistent, marked immunogenicity which is at least similar to that of its constituent vaccines used together and with a tolerability profile that is possibly improved. An accelerated, day-0, -7 and -21 regimen has also shown immunogenicity similar to that of the monovalent vaccines given concurrently, and now has an emerging role in adults likely to travel to hepatitis A virus (HAV) and/or hepatitis B virus (HBV) endemic regions within 1 month. The adult vaccine appears effective and generally well tolerated when given concurrently with monovalent typhoid vaccine (Typherix). Immunogenicity of the two-dose paediatric vaccine is high and appears to be similar whether administered as a month-0, -6 or month-0, -12 schedule and when compared to that of the three-dose paediatric vaccine (months 0, 1, 6), both of which provide a similar degree of protection to the adult vaccine. Although both preparations also provide high end-of-schedule seroprotection against hepatitis B surface antigen, protection between the first and second doses of the two-dose regimen appears lower than with the three-dose schedule. Therefore, the three-dose paediatric vaccine is a practical option in individuals at risk of immediate exposure to HBV, while the two-dose regimen may have an important function in immunisation programmes in regions where such risk is low. Combined hepatitis A and B vaccines are generally well tolerated. The most frequently reported adverse events in clinical trials were injection-site pain and redness, and general fatigue and headache; most events were mild and transient. Pharmacoeconomic models suggest the combined vaccine is cost effective compared with no vaccine (in children/adolescents) or monovalent hepatitis B vaccine (in children/adolescents and prison inmates).

CONCLUSION

The three commercially available combined hepatitis A and B adult and paediatric vaccines are highly immunogenic and generally well tolerated; the adult vaccine demonstrates immunogenicity at least as marked as that of monovalent hepatitis A and B vaccines. While further research is required to confirm potential advantages such as improved cost effectiveness, the combined vaccines have established a key role in the prevention of hepatitis A and B in defined risk groups, and have an expanding role in population-based vaccination programmes with younger age groups.

Current immunizations for travel

PURPOSE OF REVIEW

International travelers may be at risk from a variety of potentially severe and life-threatening infections. Some of these diseases are preventable, and vaccination remains a cornerstone of travel medicine. Vaccines that are important for international travel are reviewed, in a succinct update based on the most recent literature.

RECENT FINDINGS

Discussed are vaccines for enteric infections (polio, cholera, hepatitis A, and typhoid), as well as those for hepatitis B, Japanese encephalitis, yellow fever, and meningococcal vaccines. The controversial end to the polio eradication campaign and the recognition of vaccine-derived polioviruses are discussed. New monovalent cholera vaccines, including the live attenuated Peru-15 and CVD 103-HgR and the oral killed whole cell B subunit vaccine are reviewed, as well as a new oral bivalent vaccine that may offer protection against Vibrio cholerae 0139. Advances in typhoid vaccination include promising preclinical and clinical trial results of recombinant ZH9 and CVD 908-htrA vaccines, which, in addition to providing protection against typhoid fever, may be useful vectors for heterologous antigens. A growing recognition of rare adverse reactions to the 17D yellow fever vaccine, especially postvaccinal encephalitis, has led to a reassessment of its risks and benefits. Development of a novel chimeric vaccine may improve the safety and efficacy of the current Japanese encephalitis vaccine. Vaccination for meningococcal disease is characterized by the need for polyvalent, conjugate vaccines as well as a product that affords protection against serotype B.

SUMMARY

This travel vaccination review highlights progress in new travel-related vaccine development and updates the reader on issues surrounding licensed products. It will be useful for generalists, infectious disease physicians, and travel medicine specialists.