Vaccines against hepatitis

Percutaneous injuries of dental personnel at the University of the West Indies, School of Dentistry

AIM

To report the results of a survey of all percutaneous injuries occurring in 2003-2004 to staff and students at the dental school in Trinidad.

METHOD

Data were collected via 163 questionnaires administered to all dental surgery assistants, the current clinical students (years 3, 4 & 5), the interns, part-time and full-time academic staff.

RESULTS

A 71% response rate was obtained. The number of persons reporting one or more sharps injuries at the dental school was 42 (37%). Of these, 17 (40%) were percutaneous. Needlesticks and periodontal scaler injuries were the most common. There was no significant correlation (p>0.05) between injury and gender, age group, dominant hand or needle recapping technique. 75% of respondents described their concern of contracting a blood-borne disease from a sharps injury as "high" and 59% of the respondents followed the school's recommended protocol following the injury. 50% of the injuries among the students and interns were not reported.

CONCLUSIONS

A more rigorous programme of risk management with respect to sharps injuries needs to be designed and implemented at the school. There is also a need to improve surveillance of and reduce the underreporting of these injuries.

Persistence of anti-HBs antibodies in health care personnel vaccinated with plasma-derived hepatitis B vaccine and response to recombinant DNA HB booster vaccine

Long-term persistence of specific antibodies after primary immunization against HBV infection has been reported. In this study, we evaluated the persistence of anti-HBs in vaccinees 6 years after primary immunization and the response to a booster dose using a recombinant DNA yeast-derived HB vaccine. An 85.4% seroprotection rate was observed after 6 years with a significantly higher seroprotective rate in those subjects who received four doses of vaccine primary immunization as compared with those who received three doses (93.9% versus 67.2%, p < 0.001). One month after receiving the booster dose, 98.6% of the subjects had an anamnestic type of response. The GMTs were found to decrease progressively with increasing age. The antibody levels after booster dose were higher than those attained at the end of primary immunization and reflected the trend seen before the administration of the booster. These results are consistent with the existence of an effective immunological memory in HB vaccine responders. Subjects who received four doses during primary immunization were better seroprotected and had a higher seroprotection rate after the booster dose.

Hepatitis B vaccination and infection control practices of Jordanian clinical dental students

The knowledge of occupational hazards from blood-borne viruses, and practices related to cross-infection control were studied in Jordanian dental students. A survey in July 1990 showed that over 90% were aware of the existence of vaccines against hepatitis B virus and most appreciated the possible long-term hepatic sequelae of hepatitis B virus infection. Nearly 50% had already been immunized against hepatitis B and a further 4% intended to be vaccinated. Autoclaves were used by more than 80% for the sterilization of dental instruments.

Hepatitis B vaccination and infection control in Brazilian dental practice, 1990

The aims of the study were to examine the knowledge of occupational hazards from blood-borne viruses, and practices related to cross-infection control in Brazil, by a survey of 947 Brazilian dental practitioners at a National Dental Congress in January 1990. Over 80% were aware that hepatitis B virus can be present in the oral cavity and constitutes an occupational hazard but their perceptions as to the hazards from other agents were at variance with the published evidence. Over 75% were aware of the existence of vaccines against hepatitis B virus but less than 60% appreciated the possible long-term hepatic sequelae of hepatitis B virus infection and, less than 40% were aware of the oncogenic potential. Less than 10% had been immunized against hepatitis B and only a further 30% intended to be vaccinated. Autoclaves were used by less than 10%: most appeared to use chemical means for disinfection of dental instruments. These results indicate the urgent need for a campaign to improve infection control procedures in Brazilian dental practice.

Comparison of immunogenicity of recombinant and plasma derived hepatitis B antigen in guinea-pigs

Four different preparations of hepatitis B antigen (HBsAg) were tested in parallel with respect to their ability to elicit anti-HBs in guinea-pigs. We compared the effect of low doses (5 micrograms single dose and 30 micrograms total amount) of human plasma derived and recombinant HBsAg, in purified forms or prepared as vaccines, respectively. The highest titre of anti-HBs developed was detected in guinea-pigs immunized with plasma derived HBsAg, followed the by response in animals immunized with plasma derived vaccine. Purified recombinant antigen and recombinant vaccine exhibited poor immunogenicity compared with plasma derived antigen preparations. The increase in the dose of recombinant antigen (150 micrograms total amount) resulted in markedly improved response in two out of ten animals. Anti-HBs immunoglobulin fractions from pooled sera within each group of animals were isolated, partially purified, coupled to polystyrene beads and subsequently used in immunoradiometric assay with monoclonal 125I-anti-HBs. Only the anti-HBs isolated from pooled sera of animals immunized with purified plasma derived antigen met the requirements for high sensitivity and antigen specificity in such assay. Comparable properties were exhibited by the anti-HBs obtained from one guinea-pig immunized with a larger amount of recombinant antigen. With these two anti-HBs immunoglobulin preparations, amounts as low as 1 ng of HBsAg could be detected.

Awareness and acceptance of the hepatitis B vaccine by dental practitioners in Malaysia

A postal survey of 730 Malaysian dental practitioners was undertaken to assess their awareness and acceptance of the plasma derived hepatitis B vaccine. Only 32% of the 325 practitioners who responded had been vaccinated, 41% intended to be and 15% categorically refused vaccination. The main reservations about vaccine acceptance were fear of side effects including AIDS, cost of the vaccine and lack of information. Vaccine efficacy was not confirmed by serology in two-thirds of the vaccinees and two-fifths of the respondents were unaware that 5% of the vaccinees do not develop a successful antibody response after vaccination. Seventy-eight percent of dentists believed that their risk of contracting hepatitis B was high or very high while 71% recalled having received needle stick injuries in the 3 yr prior to the survey. Only 13% of respondents were aware of delta hepatitis while 63% were aware of non-A non-B hepatitis. The survey has highlighted the need for dissemination of information on hepatitis B vaccine among dentists in Malayasia.

Persistence of specific antibodies after hepatitis B vaccination

Antibody levels to hepatitis B surface antigen (anti-HBs) in healthy adults vaccinated with three doses of plasma-derived hepatitis B vaccine, containing 20, 10 or 5 micrograms of antigen, were followed for 4-6 years. After vaccination, 1034 of 1076 individuals had developed anti-HBs and 1016 had antibody concentrations above 10 IU/l. 681 of all initial responders could be tested after 1 year, 520 after 2, 380 after 3 and 213 after 4 years. 72 and 39 individuals, respectively, of the 185 earliest vaccinated volunteers were available for retesting after 5 and 6 years. Four years after the first vaccination, anti-HBs levels in 34% had dropped below 10 IU/l. The persistence of anti-HBs above this value depended on the peak antibody response after the third vaccination. Whereas all vaccinees tested with peak anti-HBs levels above 10,000 IU/l still had levels above 10 IU/l after 6 years, no-one with initial values between 10 and 100 IU/l maintained antibody concentrations above 10 IU/l for longer than 4 years. The rate of decrease in anti-HBs was independent of the peak anti-HBs value, the vaccine dose, and the age and sex of the vaccinees.

The Florey lecture, 1986. Vaccine prevention of virus-induced human cancers

Carcinogenic viruses have been discovered in numerous animal species over the last 80 years but their role in human cancer has only recently become an important issue. With EB virus involved with endemic Burkitt's lymphoma and undifferentiated nasopharyngeal carcinoma, hepatitis B virus with primary liver cancer, papilloma viruses with carcinoma of the cervix, and T-cell leukaemia virus with adult T leukaemia, 20-25% of all human cancer appears to have a virus component in its causation. By analogy with certain virus-induced animal cancers, vaccine prevention of infection should greatly reduce subsequent tumour development; vaccines against hepatitis B virus are already on trial for this purpose in populations at risk. Experiments are described in which an EB virus subunit vaccine consisting of the virus-determined membrane antigen glycoprotein molecule of molecular mass 340 kDa (MA gp340) has been prepared by two purification methods. Material from one of these has successfully protected cotton-top tamarins against a 100% lymphomagenic dose of challenge virus and investigations are under way to identify an immunogen, based on MA gp340, suitable for use in man. Genetically engineered bacterial, yeast, and mammalian cells expressing the gp340 gene are already available; this gene has also been inserted into vaccinia and varicella virus vectors. Powerful new adjuvants are also considered, together with future strategies for human vaccine studies.

Vaccination against Epstein-Barr virus: current progress and future strategies

A vaccine derived from the high-molecular-weight glycoprotein (gp340) component of the Epstein-Barr (EB) virus membrane antigen conferred complete protection against a 100% lymphomagenic dose of EB virus in the cottontop tamarin, the animal of choice for experiments with EB virus. The membrane-antigen gene has already been cloned, and the development of a vaccine for use in man should now be possible. Such a vaccine could be tested first against infectious mononucleosis, because the effectiveness of vaccination would become evident in a relatively short time. Field trials against Burkitt's lymphoma and nasopharyngeal cancer could follow.