The hepatitis B vaccine
HBV vaccine contains recombinant HBsAg particles adsorbed on to aluminium hydroxide adjuvant which induce antibodies to HBsAg.
A combined vaccine containing purified inactivated hepatitis A virus and purified recombinant HBsAg, separately adsorbed onto aluminium hydroxide and aluminium phosphate, is also available.
It should be pointed out that mercury-based Thiomersal is not used as a preservative in hepatitis B vaccines available in the UK. Thiomersal is still used in the production process for Engerix-B, Twinrix, Ambirix and Fendrix, and therefore residues are present in the final product.
Around 10 to 15% of adults do not respond to the three dose schedule of vaccine or respond poorly. Poor responses are identified with individuals older than 40 years, smokers and the obese. Patients with advanced liver disease, who are immunosuppressed or on renal dialysis, and patients with concomitant hepatitis C may also have lower seroconversion rates. Individuals who are anti-HBs and anti-HBc positive are immune and do not require vaccination.
Vaccination can also provide high levels of protection when given shortly after exposure. In these situations it is important to commence vaccination as soon as possible (ideally within 24 hours) and to complete the vaccination schedule on time. Vaccination should not be delayed whilst awaiting further information or blood test results.
Specific hepatitis B immunoglobulin (HBIG)
HBIG provides passive immunity and thus can confer immediate, albeit temporary, protection after accidental exposure to HBV-infected blood.
HBIG is given concurrently with HBV vaccine as it does not alter the development of active immunity. HBIG gives rapid protection after exposure until the hepatitis B vaccine becomes effective. Both the vaccine and HBIG should be given as soon as possible, preferably within 12 hours, ideally within 24 hours, although it should be considered up to a week after exposure. Babies born to mothers known to be very infectious during antenatal screening should be given HBIG as well as vaccine immediately after birth.
HBIG is obtained from the plasma of immunised and screened human donors. The theoretical risk of transmission of variant CJD from plasma products means that HBIG used in the UK is now prepared from plasma sourced from abroad and as a result supplies are somewhat scarce.
Administration
HBV vaccine is routinely given intramuscularly in the upper arm or anterolateral thigh. The buttocks are not used, as absorption may affect the vaccine efficacy. Patients who have bleeding disorders should receive their vaccination by deep subcutaneous injection.
HBIG can be administered in the upper outer quarter of the buttock or the anterolateral thigh.
Where administration of both the vaccine and HBIG is required these should be at different sites.
Schedules for pre-exposure and post-exposure prophylaxis
Pre-exposure immunisation is used for individuals who, because of lifestyle, occupation or other factors, are at increased risk of hepatitis B.
Post-exposure prophylaxis is recommended for babies born to HBVinfected mothers and persons accidentally inoculated or contaminated by exposure to potentially infected blood or body fluids.
The schedule requires a minimum of three doses with or without a fourth booster dose. The exception is for children given adult strength vaccines where two doses are sufficient. Children aged one to 15 can receive two doses of Ambirix or children aged 11 to 15 can receive Engerix B, at zero and six months.
In most risk groups and for post-exposure prophylaxis, an accelerated schedule should be used. The vaccine is given at zero, one and two months. For those who are at continued risk, a fourth dose is given at 12 months. An alternative schedule of zero, one and six months can be used but only where rapid protection is not required and there is a high likelihood of compliance.
An extension to the product licence for Engerix-B has been granted to allow for a very rapid immunisation schedule of three doses given at zero, seven and 21 days. When this schedule is used, a fourth dose should be given 12 months after the first dose. This schedule is licensed for use on occasions where people over the age of 18 are at immediate risk and a faster induction of protection is necessary (persons travelling to areas of high endemnicity, IDUs and prisoners).
Individuals at continuing risk of infection should be offered a single reinforcing dose after five years.
Those at risk of occupational exposure, such as healthcare and laboratory workers have the right to know if they have been protected under the Control of Substances Hazardous to Health (COSHH) regulations.
Antibody titres should be checked one to four months after completion of the primary vaccination course. Anti-HBs levels above 100mIU/ml are desired. Those with levels of 10 to 100mIU/ml should receive one additional dose of vaccine at that time and a reinforcing dose at five years as recommended above. An antibody level below 10mIU/ml is classified as a non-response. They will need testing for current or past infection, and a repeat course of the vaccine is recommended followed by re-testing. Those who still do not respond will require HBIG protection if exposed to the virus.