Hepatitis B vaccines have been available for more than two decades, but infection with the hepatitis B virus (“HBV”) remains a worldwide health problem. Globally, more than two billion individuals present with serological evidence of HBV infection. Of these, 240 million are chronic carriers and approximately 780,000 hepatitis B-related deaths occur annually.
Second-generation hepatitis B vaccines, which use the HBV surface S antigen to create an immunologic response in vaccine recipients, have been shown to effectively prevent infection in young individuals. Older persons, however, do not respond as well to these currently licensed vaccines. Hepatitis B vaccine failure is often explained by immunosenescence (the gradual deterioration of the immune system brought on by aging), or by immunosuppression, including conditions such as obesity, renal failure, HIV infection, and diabetes.
About Hepatitis B
Hepatitis B Vaccine Approaches
Exposure Risks for healthcare workers
Healthcare workers (“HCW”) include all persons working in a healthcare setting who may be exposed to infectious materials, including blood or body fluids. HBV is most commonly transmitted via needle-stick; HCWs who are stuck by a HBV-infected needle have a 22 to 31% chance of developing hepatitis B. HBV can also be spread through direct contact with mucous membranes and non-intact skin including wounds, cuts, and burns. HBV is highly infectious and can survive for up to seven days on some surfaces.
Since hepatitis B vaccines became available in 1981, the U.S. Advisory Committee on Immunization Practices (“ACIP”) has recommended that all HCW’s at risk of acquiring or transmitting HBV be vaccinated. From 1983 to 2010, HBV infections in HCWs declined 98%. Despite this success, there are improvements to be made, including time-to-protection, as new factors place HCWs at an increased risk of contracting HBV.
European refugee crisis
Europe is currently facing the worst refugee crisis since World War II. Many of these migrants have fled countries with limited vaccination coverage, such as Syria, Iraq, and Afghanistan. The World Health Organization (“WHO”) suggests that the influx of migrants with limited vaccination protection is shifting the disease burden in Europe. A study conducted by a refugee center in Germany found that the vaccination rate was only 18.6% for arriving refugees, and 62% had no immunity to HBV. Moreover, the serological markers of HBV infection, HBsAg and anti-HBc, were found in 2.3% and 14% of people tested, respectively. This was in-line with other migrant populations in Germany and higher than the native German controls.
Migration into the European Union from countries with high rates of HBV is increasing disease prevalence in many European countries. In Germany, despite accounting for only 12.7% of the population, migrants accounted for 42% of chronic carriers of HBV. These shifting demographics increase the risk of HBV exposure for HCWs.
Dosing schedule for second-generation vaccines
Hepatitis B vaccination commonly consists of three doses of vaccine administered intramuscularly into the patient’s shoulder on a 0, 1, and 6-month schedule.
In otherwise healthy individuals, immunization with second-generation vaccines is effective in 30-55% of people who take only one dose, up to 75% who take two doses, and in over 90% of patients who finish the series. In order ensure that a HCW is protected, the individual must receive all three vaccinations.
Higher risk of HBV infection has been reported in HCWs during the professional training period and it is recommended that the vaccination series be completed before trainees potentially have contact with blood. A more immunogenic hepatitis B vaccine may offer earlier seroprotection, potentially after two doses. This would enable HCWs to be protected within approximately three months of initial vaccination, rather than six or more months.
From 2005 to 2010, 203 HCWs contracted acute hepatitis B in the U.S and were reported to CDC’s National Notifiable Diseases Surveillance System (“NNDSS”). Only 35 of the 203 reported complete vaccination with three doses. Among those 35, 34 of them were non-responders. They were vaccinated appropriately, but were not protected by currently licensed second-generation vaccines. A more immunogenic hepatitis B vaccine may improve seroprotection in vaccine non-responders.
Changing patient demographics may increase exposure risk
The U.S. population is aging and there are an increasing number of individuals in long term care facilities. Although hepatitis B vaccine coverage is high in infants, children, and adolescents, coverage remains lower in adult populations, potentially putting HCWs who work with the elderly at an increased risk of infection.
Immunization requirements for healthcare workers
Despite the risk of HBV transmission to HCWs in both the U.S and Europe, vaccination protocols vary greatly from country to country. In the U.S, immunization regulations for HCWs are set on a state-by-state basis. However, in 1991, the Occupational Safety and Health Administration (“OSHA”) issued a Federal Standard that required employers to offer hepatitis B vaccination at no-cost to all occupationally exposed people. And in 2013, the U.S. Centers for Disease Control and Prevention (“CDC”) recommended that all HCWs receive three or more doses of a hepatitis B vaccine as well as testing to ensure HBV immunity.
Still, very few states either require screening or proof of immunization for hepatitis B in HCWs. Due to the lax regulations set by states, hospitals have substantial autonomy in setting HCW vaccination policies, and there is great variability across the U.S.
In Europe, seven out of 29 countries surveyed have a universal hepatitis B screening process for all HCWs. Eight additional countries screen workers only when they are occupationally exposed to the virus. Interestingly, even though every European Union country recommends that HCWs be vaccinated against hepatitis B, not all of them require screening for it. These inconsistent recommendations and policies leave many HCWs in both the U.S and Europe susceptible to hepatitis B.
Sci-B-Vac®: A Third-Generation Hepatitis B Vaccine
To overcome potential limitations of the second-generation hepatitis B vaccines, VBI developed a third-generation vaccine that contains all three hepatitis B virus surface proteins (S, pre-S1, and pre-S2). By mimicking the hepatitis B virus as it is found in nature, Sci-B-Vac® may provide more opportunity for the immune system to respond with antibodies that can recognize components of the virus, which may lead to more rapid and potent protective immunity.
To learn more about Sci-B-Vac®, visit: https://www.vbivaccines.com/sci-b-vac/