Controlling hepatitis B virus transmission in North America. The North American Regional Study Group

Design, synthesis, and biological evaluation of triazolo-pyrimidine derivatives as novel inhibitors of hepatitis B virus surface antigen (HBsAg) secretion

The high levels of hepatitis B virus (HBV) surface antigen (HBsAg)-bearing subviral particles in the serum of chronically infected individuals play an important role in suppressing HBV-specific immune response and are only mildly affected by the current small molecule therapies. Thus, a therapy that specifically reduces HBsAg serum levels could be used in combination therapy with nucleos(t)ide drugs or permit therapeutic vaccination for the treatment of HBV infection. Herein, we report the design, synthesis, and evaluation of novel triazolo-pyrimidine inhibitors (1, 3, and 4) of HBsAg cellular secretion, with activity against drug-resistant HBV variants. Extensive SAR led to substantial improvements in the EC(50) of the parent compound, 5 (HBF-0259), with the best being 3c, with EC(50) = 1.4 ± 0.4 μM, SI ≥ 36. The lead candidates, both 1a (PBHBV-001) and 3c (PBHBV-2-15), were well-tolerated in both normal and HBV-transgenic mice and exhibited acceptable pharmacokinetics and bioavailability in Sprague-Dawley rats.

Repeat HIV testing, risk behaviors, and HIV seroconversion among young men who have sex with men: a call to monitor and improve the practice of prevention

OBJECTIVES

We compared recent risk behaviors and HIV seroconversion among young men who have sex with men (MSM) who were first-time, infrequent, and repeat HIV testers.

METHODS

Male adolescents and young men aged 15 to 22 years were randomly sampled, interviewed, counseled, and tested for HIV at 194 gay-identified venues in seven U.S. cities from 1994 through 1998. Analyses were restricted to MSM who reported having never tested or last tested HIV-negative.

RESULTS

Of 3430 participants, 36% tested for the first time, 39% had tested infrequently (one or two times), and 26% had tested repeatedly (> or = three times). Compared with first-time testers, repeat testers were more likely to report recent risk behaviors and to acquire HIV (7% versus 4%). Over 75% of repeat testers who seroconverted acquired HIV within 1 year of their last test. Compared with repeat testers, first-time testers reported similar use of health care but delayed testing for nearly 2 additional years after initiating risk.

CONCLUSIONS

Many young MSM soon acquire HIV after repeated use of HIV counseling and testing services. Providers must strengthen practices to identify, counsel, and test young MSM and provide enhanced behavioral interventions for those with persistent risks.

Two decades after vaccine license: hepatitis B immunization and infection among young men who have sex with men

OBJECTIVES

This study investigated hepatitis B immunization coverage and the extent of hepatitis B virus (HBV) infection among young men who have sex with men (MSM), a group for whom hepatitis B vaccine has been recommended since 1982.

METHODS

We analyzed data from 3432 MSM, aged 15 to 22 years, randomly sampled at 194 gay-identified venues in 7 US metropolitan areas from 1994 through 1998. Participants were interviewed, counseled, and tested for serologic markers of HBV infection.

RESULTS

Immunization coverage was 9% and the prevalence of markers of HBV infection was 11%. HBV infection ranged from 2% among 15-year-olds to 17% among 22-year-olds. Among participants susceptible to HBV infection, 96% used a regular source of health care or accessed the health care system for HIV or sexually transmitted disease testing.

CONCLUSIONS

Despite the availability of an effective vaccine for nearly 2 decades, our findings suggest that few adolescent and young adult MSM in the United States are vaccinated against hepatitis B. Health care providers should intensify their efforts to identify and vaccinate young MSM who are susceptible to HBV.

Geographic origin and risk for congenital infection in a Canadian inner city: findings and implications for policy

This study examines associations between geographic origin and risk for congenital infections, through a chart review of women from the St. James Town area of Toronto delivering at Wellesley Hospital in 1996. Foreign-born women (n = 203) were significantly less likely than Canadian-born women (n = 53) to be HBsAg negative (187/193 vs. 48/48; RR = 0.97, 95% CI 0.94-0.99). There was no significant difference in rubella seronegativity, but rubella immunity was unacceptably low in both groups (less than 90%). A number of rubella non-immune women had delivered previously in Canada. Procedures must be implemented to ensure completion of hepatitis B immunization series in affected newborns, and rubella immunization in seronegative women prior to discharge. As well, updating immunization status most become a routine part of the immigration medical examination.

Evaluating the cost-effectiveness of vaccination programmes: a dynamic perspective

Although there are many models which are used to calculate the health benefits (and thus the cost-effectiveness) of vaccination programmes, they can be divided into two groups: those which assume a constant force of infection, that is a constant per-susceptible rate of infection; and those which assume that the force of infection (at time t) is a function of the number of infectious individuals in the population at that time (dynamic models). In constant force of infection models the per-susceptible rate of infection is not altered, whereas in dynamic models mass immunization results in fewer infectious individuals in the community and thus a lower force of infection acting on those who were not immunized. We take an example of each of these types of model, examine their underlying assumptions and compare their predictions of the cost-effectiveness of a mass immunization programme against a hypothetical close contact infection, such as measles. We show that if cases of infection are the outcome of interest then the constant force of infection model will always underestimate the cost-effectiveness of the immunization programme except at the extremes when no one or everyone is immunized. However, unlike the constant force of infection model, the dynamic model predicts an increase in the average age at infection after immunization which could impact on the estimate of the cost-effectiveness of the programme if the risk of developing serious disease is a function of the age at infection (as, for instance, is the case for congenital rubella syndrome). Taking cases of infection as the outcome measure and using the dynamic model, the undiscounted cost-effectiveness ratio will tend to decline over time and approach a constant value, as the system moves from pre- to post-immunization equilibrium. We go on to show how the cost-effectiveness of a fixed-term immunization programme might change over time, and discuss why, under most circumstances, decision makers should not assume that elimination (permitting termination of mass immunization) will occur.

Comprehensive control (or elimination) of hepatitis B virus transmission in the United States

In the United States, the reported rate of hepatitis B has declined by over 50% since 1987, probably as a result of vaccination programmes, behavioural changes, refinements in blood screening procedures, and the availability of virus inactivated blood components. The majority of new hepatitis B infections occur in 20-39 year olds, and perinatal transmission is uncommon except in certain at risk groups. Initial efforts to control hepatitis B in the US were targeted at high risk groups, including health care personnel. Then, in 1988, the Centers for Disease Control and Prevention (CDC) recommended screening of all pregnant females for hepatitis B surface antigen and full immunisation of infants born to those testing positive. A recommendation for universal immunisation of infants was endorsed in 1991. Compliance has been slow but progressive. The CDC also has recommended 'catch up' immunisation of adolescents and high risk children and adults. Demonstration projects suggest that these can be successful, given the provision of free or low cost vaccine and appropriate support. Hepatitis B vaccination has been shown to be cost effective and should be integrated into the routine childhood immunisation schedule. Responses to hepatitis B vaccine have largely been shown to be durable, although at least one booster dose after five to 10 years seems prudent, especially if a low dose, yeast derived vaccine has been used.

Strategy for vaccination against hepatitis B in areas with high endemicity: focus on Korea

Hepatitis B vaccination strategies may vary from country to country depending on hepatitis B virus (HBV) endemicity, predominant modes of infection, age of infection, and health care resources. In areas with high endemicity like Korea, transmission of virus from carrier mothers to infants during the perinatal period, and from other horizontal sources to infants and children, account for most cases of HBV infection. The consequences of HBV infection at an early age are serious, as more than 70% remain chronic carriers of the virus. These chronic carriers are the principal source of infection for other susceptible people, and are themselves at high risk of developing other serious diseases, such as chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Theoretically, therefore, routine infant immunisation supplemented with prenatal screening of pregnant women for HBsAg or HBeAg and mass immunisation of children is the appropriate strategy for control of hepatitis B in these countries. To prevent primary liver cancer associated with HBV infection, however, immunisation of adults at high risk would also be prudent. Mandatory vaccination of all neonates is recommended in highly endemic areas, together with hepatitis B immune globulin in babies born to HBsAg carrier mothers.

Control of hepatitis B through routine immunization of infants: the need for flexible schedules and new combination vaccine formulations

Universal immunization of infants is essential to the control of hepatitis B in areas of high endemicity where infection commonly occurs in infants and children. It is also an attractive strategy for ultimately reducing hepatitis-B-associated acute and chronic liver disease in areas of lower endemicity where infections occur primarily in adolescents and adults. Integration of hepatitis B vaccine with other routine paediatric immunizations, using flexible scheduling, will enhance compliance while minimizing the need for additional resources. Clinical studies demonstrate that a very high proportion of healthy infants and adults develop a protective level of antibody when given hepatitis B vaccine using a wide range of schedules. Compliance with universal vaccination of infants against hepatitis B may be enhanced by the development of new combination vaccines (e.g. diphtheria-tetanus-pertussis-Haemophilus influenzae b-hepatitis B) that allow complete immunization against several antigens with a minimal number of injections.