Hepatitis B Vaccination and Hepatitis B Prevention

Hepatitis B virus (HBV) is usually spread parenterally or by intimate sexual contact.
This is usually from blood or blood products, whether by intentional transfusion or sharing injection equipment or implements for tattooing.
Exposure to HBV can produce a variety of different states:¹

• 60-65% show subclinical disease and recover fully
• 20-25% develop acute hepatitis
• 5-10% become "healthy" carriers i.e. HBsAg +ve after 6 months
• 5-10% develop chronic hepatitis
• Those that carry the antigen HBsAg are not at high risk of transmitting the disease, unless they also carry the antigen HBeAg.
• Carriers of HBeAg are very infectious.

Prevalence

The incidence of acute Hepatitis B and prevalence of its chronic carrier state varies widely across the globe.
In areas with high endemicity (HBsAg prevalence ≥ 8%; e.g. South East Asia and Africa), more than half of the population becomes infected at some point in their lives.²In countries with low endemicity (HBsAg prevalence ≤ 2%; e.g. North America, Western Europe, Australia), most of the population do not become infected.
Nearly a third of the world population has been infected by hepatitis B at some point, and at least 350 million people are currently chronic carriers of Hepatitis B infection.³
The number of new infections per year was approximately 60,000 in 2004.⁴
Highest rate of disease occurs in 20-49-year-olds.
Greatest decline has happened among children and adolescents due to routine hepatitis B vaccination.
The estimated frequency of infectious donations entering the blood supply during 1996-2003 was 1.66 per million for Hepatitis B and 0.80 per million for Hepatitis C.⁵
Considering the different demography of blood donors and those at risk this is likely to be an underestimate of total prevalence.

Incidence

In England and Wales from 1995 to 2000 laboratory data suggested that the annual incidence of HBV infection was 7.4 per 100,000. Antenatal surveillance in London found about ten in 1000 women were HBsAg positive.⁶

• Injecting drug use as the commonest cause of transmission.
• The number of cases attributed to heterosexual contact was fairly stable, whereas the number of cases in homosexual men decreased.
• Transmission during childhood was rare, but more frequent among South Asians.
• The incidence in South Asians is relatively high, and their main risk factors are medical treatment overseas and heterosexual contact.
• A proportion of cases have no reported route of transmission, but it is likely that many are related to injecting drug use.

The main risk groups are:

• Intravenous drug abusers.
• Sexual promiscuity, especially amongst homosexual men.
• People who have received medical treatment, especially blood transfusion in countries that do not screen for HBV are at increased risk.
• People who have received much blood or especially pooled blood products in former years are at great risk. This is particularly applicable to haemophiliacs.
• Vigilance is required to keep the disease out of haemodialysis units.
• HBV can be spread from mother to child during pregnancy, delivery or breast feeding.
  • Most adults infected with the virus recover fully and develop lifelong immunity but babies infected at birth have about a 90% risk of persistent infection.⁷
  • Children infected between 1 to 10 years have about a 25% chance of persistent infection.
  • In adults the figure is 2 to 10%.
  • About 20% of those infected in infancy or childhood will develop cirrhosis or liver cancer later in life.
• Immigrants from areas of high prevalence can represent a source of infection.
• Urine, faeces, saliva, sputum, tears, sweat and vomit do not pose a risk of HIV, Hepatitis B or C unless they are contaminated with blood.

Hepatitis B vaccine is safe and effective but should not be seen as an alternative to a strategy of prevention of transmission.

• The standard course of immunisation involves 3 injections at 0,1 and 6 months.
• An accelerated course of 0,1 and 2 months is possible
• Adults who need protection very quickly can have a schedule of 0,7 and 21 days. The vaccine is administered intramuscularly, usually into the deltoid muscle.
• After an accelerated course a booster at 1 year is recommended.

It can be used in those who are immunocompromised, as with HIV infection, but a higher dose may be required or extra booster injections.
The vaccine should be given into the deltoid region or anterior thigh in babies.
It is less effective if given into the buttock
It is quite possible that a course may give life-long immunity,⁸ but for heath professionals a booster every 5 years is recommended in those with good antibody response.
Antibody titres should be tested in health professionals 2 to 4 months after the primary course.

• A titre above 100miu/ml is regarded as adequate.
• Around 10-15% of adults fail to respond to three doses of vaccine or respond poorly.⁹
• Poor responders with titres of 10 to 100miu/ml should have a booster and those with a titre below 10miu/ml should repeat the course.
• Those over 40 years old, who are obese or who smoke are more likely to fail to respond.
• Alcoholics are also reported as having lower seroconversion rates, particularly those with advanced liver disease.
• Patients who are immunosuppressed or on renal dialysis may also respond less well and require larger or more doses of vaccine.
• Failure to produce any antibody after 2 complete courses should not be seen as necessarily meaning no immunity as immunity to the disease is largely cell-mediated rather than by antibody.

• Post- exposure prophylaxis (PEP) involves giving Hepatitis B vaccine and possibly immunoglobulin too if required.
• Immunoglobulin is given at a different site and it does not reduce the immune response to the vaccine.
• If the status of the source is unknown assume infection.
• PEP may be indicated even if the exposed person has received Hepatitis B vaccine previously.
• It should be given within 48 hours and certainly no later than 7 days after exposure.
• The incubation period of the disease is 40 to 160 days.

If the site of exposure is a needle-stick injury, cut or abrasion the site should be immediately washed with soap and water.
It is indicated for babies born to mothers who are chronic carriers of hepatitis B virus or to mothers who have had acute hepatitis B during pregnancy.
More details about PEP can be found in "The Olive Book", "Hepatitis B immunization" and "Guidance for clinical healthcare workers", see websites listed below.

Adverse reactions to the vaccine are few and usually mild.
There may be some soreness and erythema around the site.
Fatigue, malaise and influenza-like symptoms are rarer.
An association with a Guillain-Barre type syndrome has not been substantiated.

Evidence shows that universal vaccination in countries with a high endemic incidence of Hepatitis B is beneficial.¹⁰
The benefit in countries with a low endemic incidence is much less and the most effective management is selective immunization of high risk groups within those countries. Accelerated courses are probably best for drug abusers as they are notoriously difficult to get to complete a course.
Even with immunization it is essential to take all necessary precautions to prevent transmission of the virus.