anthrax vaccination

Last edited 04/2019

Anthrax vaccination is made available to those at risk of exposure due to their occupation i.e. those handling imported wool, hides or bone meal. In some countries, there is active immunisation of animals with live attenuated spores.

• vaccine is made from antigens found in the sterile filtrate from cultures of the Sterne strain of Bacillus anthracis. These antigens are adsorbed onto an aluminium adjuvant to improve their immunogenicity and are preserved with thiomersal
• vaccine is inactivated, does not contain live organisms and cannot cause the disease against which it protects
• no formal efficacy trials with the UK vaccine
  • in 1958, the introduction of vaccine successfully controlled cutaneous anthrax at a government wool disinfecting station in Liverpool
  • a controlled clinical trial was carried out in the 1950s among workers in goat-hair mills in New Hampshire, USA, using a vaccine similar to that currently licensed in the USA and the UK
    • although the study did not have sufficient power to accurately measure protection against pulmonary anthrax, no cases occurred in the vaccinated group compared with five in the unvaccinated
• there have been no recorded cases of anthrax infection in individuals vaccinated in the UK.

The objective of the anthrax vaccination is to provide a minimum of four doses at appropriate intervals for individuals at high risk of occupational exposure. Workers dealing with infected animals where there may be a risk of occupationally acquired anthrax include:

• farm workers, e.g. livestock breeders/keepers, shepherds, dairy workers - from skin contact with, or inhalation of, spores from diseased animals, or during disposal of infected carcasses and slurry
• veterinary surgeons - from treatment of infected animals
• local authority workers - from disposal of infected carcasses
• zoo keepers - as above
• abattoir workers/butchers - from exposure to anthrax spores during preparation of animals for food and food products
• construction workers - people working in old buildings may be exposed to animal material, e.g. hair containing anthrax spores
• laboratory workers - people working in laboratories that handle specimens from infected animals and/or humans

Occupations involving processing of infected animal material A variety of industrial processes present situations where workers may be at risk of acquiring anthrax. These include those who work with/in:

• certain textiles, e.g. goat-hair, wool
• leather, e.g. importers, tanners
• rendering, e.g. glue, gelatine, tallow, bone processing . storage and distribution e.g. docks, warehousing or transport of any of the above.

Primary immunisation

When indicated, individuals in these groups who are assessed to be at risk should be offered a primary course of anthrax vaccination. The primary course of anthrax vaccination consists of four doses. Three doses of 0.5ml are given with an interval of at least three weeks between each dose. The fourth dose is given at least six months after the third dose.

Reinforcing immunisation

Potential continuous low level exposure

• are no industries In the UK in which there is a risk of continuous exposure to high levels of airborne anthrax spores - however, where the risk assessment indicates that an individual is at continuous low level risk, a single reinforcing dose of 0.5ml should be offered at 10 year intervals on up to 3 occasions to sustain protection. Further doses are not recommended as they may result in a reduced immune response

Potential intermittent high level exposure

• evidence suggests that, following a full primary course, offering a booster dose after a prolonged interval results in antibody levels superior to those seen in patients who receive annual boosters
  • therefore, individuals should be offered a single reinforcing dose of 0.5ml just before entering situations with a specific high risk of exposure. If such opportunities do not arise, in order to sustain immune memory, a single reinforcing dose should also be offered at 10 year intervals on up to 3 occasions.

Reference:

1. Immunisation Against Infectious Disease - "The Green Book".Chapter 13 Anthrax (April 2019)