Plasma-derived versus recombinant hepatitis B vaccines

Use of licensed vaccines for active immunization of the immunocompromised host

The latter part of the 20th century has witnessed an unprecedented rise in the number of individuals with impaired immunity. This is primarily attributable to the increased development and use of antineoplastic therapy for malignancies, organ and bone marrow transplantation, and the AIDS epidemic. Individuals with impaired immunity are often at increased risk for infections, and they can experience more severe and complicated courses of infection. The lack of therapy for a variety of viruses and the rise in antimicrobial resistance of many pathogens have focused attention on vaccination to prevent infectious diseases. The efficacy of most licensed vaccines has been established in immunocompetent hosts. However, there is also considerable experience with most vaccines in those with impaired immunity. We reviewed the use of licensed live, inactivated, and polysaccharide vaccines in this group, and several themes emerged: (i) most vaccines are less immunogenic in those with impaired immunity than in normal individuals; (ii) live vaccines are generally contraindicated in this group; and (iii) the efficacy of many commonly used vaccines has not been established in people with impaired immunity. This review suggests that for most vaccines there are little or no efficacy data in those with impaired immunity but their use in this patient group is generally safe.

Intradermal hepatitis B vaccination in a 300-bed primary care hospital: experience with a recombinant vaccine in a four-dose schedule

BACKGROUND

All hepatitis B vaccination programs, regardless of route, must address such factors as primary response rate, additional booster injections for primary nonresponders, antibody persistence, the need for and timing of additional booster injections for primary responders, overall costs, and medical efficacy. A voluntary intradermal hepatitis B vaccination program with postvaccination testing was implemented in a 300-bed primary care hospital with a recombinant vaccine packaged in a concentration of 20 micrograms/ml (Engerix B; SmithKline and French Laboratories, Philadelphia, Pa.).

METHODS

After informed consent was obtained, 460 employees were vaccinated intradermally over the deltoid muscle by a single employee health nurse at months 0 (initial), 1, 2, and 6, followed by testing for serologic response 1 to 2 months after the final dose.

RESULTS

Of 411 employees who completed the entire protocol, 90.5% had seroconversion, as determined by enzyme immunoassay. Twelve of 29 primary nonresponders (41%) had seroconversion after an additional (fifth) intradermal booster injection. Of the primary responders, 84.5% remained seropositive when tested 18 months after the initial vaccination injection. These results are comparable to those of intramuscular vaccination and to the original studies of intradermal vaccination with plasma-derived vaccines that had shown excellent immunogenicity.

CONCLUSIONS

Intradermal and intramuscular hepatitis B vaccination programs must be implemented in somewhat different ways, but both can provide excellent protection against hepatitis B viral infection. Even allowing for the additional expense of postvaccination testing and more frequent booster injections, intradermal vaccination greatly reduces the overall costs of hepatitis B vaccination and may therefore increase compliance in many different settings.

Non-efficacy of low-dose intradermal vaccination against hepatitis B in Down's syndrome

Persons with Down's syndrome (DS) constitute a risk group for hepatitis B (HB) and are recommended to be immunized. Of 123 persons with DS in Orebro county screened for markers of HB, 31% had such markers; 16% were potentially contagious. 83 persons without markers participated in a comparative trial of the immunogenicity of a recombinant HB vaccine given either intramuscularly (IM) or in a lower dose intradermally (ID). Immunity developed in 73% after IM vaccination as compared to 29% of those given ID vaccination (p < 0.005). At 3-year follow-up half and two-thirds of the immune persons, respectively, had lost their immunity. Those > 30 years had a poor immunization response compared to the younger ones (p < 0.01). Only 19% of the non-responders developed immunity after an IM booster dose given 10 months after the third injection. Intradermal vaccination is not warranted in persons with DS, especially not in middle aged and older persons. A booster dose of vaccine does not ascertain immunity in those who do not respond with immunity to the ordinary immunization schedule. Post-vaccination immunity should therefore be controlled.

Persistence of antibody to hepatitis B surface antigen after low-dose, intradermal hepatitis B immunization and response to a booster dose

To determine the duration of antibody after low-dose, intradermal (i.d.), plasma-derived hepatitis B vaccination and the response to a booster dose, we studied two classes of medical students who were immunized with 2 micrograms doses i.d. In one class, 73/88 (85%) who had been immunized by skilled personnel at 0, 1 and 6 months, had protective concentrations (greater than or equal to 10 mIU ml-1) of anti-HBs at 20 months after the first dose. Twelve (92%) out of 13 students who received only two doses at 0 and 1 months also had protective concentrations at month 20. At month 27, 11/16 (69%) with antibody less than or equal to 10 mIU ml-1 responded to a fourth dose of 2 micrograms i.d. with protective concentrations of anti-HBs. In the second class, after three doses of vaccine at 0, 1, and 6 months, protective concentrations of anti-HBs were present in 90/93 (97%) at 14 months and in 71/80 (89%) at 25 months. In those who received only two doses, protective concentrations were found in 24/31 (74%) at 14 months and 9/16 (56%) at 25 months. After a booster dose of 2 micrograms i.d. at month 25, anti-HBs concentrations rose from a geometric mean of 78 to 1198 mIU ml-1 in 60 subjects previously immunized with three doses and from 18 to 1054 mIU ml-1 in 16 students previously immunized with only two doses. Overall, 73/76 (96%) of students in the second group had protective concentrations of antibody after the booster dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Intradermal hepatitis B vaccination

The availability of vaccine since 1982 for immunization against hepatitis B virus (HBV) has had minimal impact on the disease; mass immunization has been suggested. Intradermal vaccination, which has precedent in prophylaxis of other infectious diseases, has been investigated as a low-cost alternative to traditional intramuscular HBV vaccination. Results of open and comparative trials indicate similar seroconversion rates for intradermal and intramuscular HBV vaccination routes in healthy adults. However, antibody titers and, presumably, duration of antibody protection appear to be decreased with intradermal HBV vaccination. Limited data suggest that demographic factors such as age and gender may affect vaccine responsiveness to intradermal HBV vaccine. Adverse skin reactions are common but do not represent a deterrent to continued intradermal HBV vaccination. There is a need for large-scale prospective comparative trials to substantiate the value of intradermal HBV vaccination. Nevertheless, the potential economic and epidemiologic benefit of intradermal vaccination justifies continued investigation for prevention of HBV infection.

The hepatitis B virus

Of all the hepatotropic viruses, HBV is associated with the greatest worldwide morbidity and mortality. This is because of the ease of transmission and the potential for progression to a chronic infective carrier state, with the complications of cirrhosis and hepatocellular carcinoma. The use of PCR has shown that some of the earlier concepts concerning the interpretation of serological data were inaccurate. Many patients with anti-HBe and anti-HBs have viral DNA detectable by PCR, and some hepatocellular carcinoma patients have detectable HBV DNA in their livers in the absence of all serological markers of HBV disease. The clearance of HBV infected cells from the liver is dependent on the interplay between the interferon system and the cellular limb of the host immune response. The importance of the nucleocapsid proteins as targets for sensitized cytotoxic T cells has been established for chronic HBV infection. The importance of pre-S sequences as inducers and targets of the virus-neutralizing humoral immune response is becoming established, but their precise role must await the development of in vitro models of hepadnavirus infection and a greater understanding of the mechanisms of viral uptake. The epidemiology and clinical course of the disease can be modified by immunization, immune stimulation and antiviral chemotherapy. For the developing world, a programme of immunization at birth would be the most effective way of eliminating this disease, but at present the cost is prohibitive. For the developed world, immunization is realistic for the at-risk population, and anti-viral and immunostimulatory therapy available for those already infected. In adult acquired chronic HBV infection alpha-interferon produces HBe antigen clearance in 40-60% of cases and is followed by resolution of the hepatic inflammation. Results in neonatally acquired infection are less impressive and prednisolone priming followed by interferon may be needed. The presence of a mutation in the pre-core region of some virus isolates has recently been described. Hepatocytes infected with this virus cannot produce HBe antigen and the course of the liver disease is fairly rapid. Whether this mutant causes liver damage in the same way as the wild virus or is directly cytopathic remains unclear, and its relationship to fulminant hepatitis is under investigation.

Effectiveness of intradermal hepatitis B immunization of hospital staff

Three doses of hepatitis B vaccine were administered via an intradermal route to 316 health service staff. One month after the final dose, 89.9% of subjects had antibodies to hepatitis B surface antigen at levels of 10 IU/l or greater. A programme of hepatitis B immunization based upon the intradermal route is substantially less expensive than one using an intramuscular technique, and can enable health authorities to provide protection for increased numbers of staff without diverting resources from other programmes of health care.

Antibody response after intradermal administration of recombinant hepatitis B vaccine in children

Intradermal vaccination with recombinant hepatitis B vaccine was performed in 33 children (mean age 3.3 years). A 2 micrograms dose was given at 0, 1 and 6 months and antibody responses were determined 20 months after the initial dose. In 32/33 children, serum antibodies to HBs were demonstrated, with a geometric mean level of 26.5 IU/l, and 24 children (73%) had anti-HBs levels greater than or equal to 10 IU/l. The results indicate that intradermal vaccination with recombinant hepatitis B vaccine may be an alternative for vaccination of small children.