Leucogen

Leucogen is available as a suspension for injection and can only be obtained with a prescription.

The vaccine is given to cats as an injection under the skin. The initial vaccination course is two injections 3 or 4 weeks apart from 8 weeks of age. In cases where the kitten may have antibodies passed from the mother, a third injection can be given from 15 weeks of age. A booster vaccination of a single injection is necessary one year after the initial vaccination course. Protection starts 3 weeks after the primary course of vaccination and lasts one year. Following the first booster vaccination protection lasts 3 years.

Leucogen is a vaccine. Vaccines work by ‘teaching’ the immune system (the body’s natural defences) how to defend itself against a disease. Leucogen contains small amounts of a protein from the outer layer of the virus called ‘envelope p45 protein’. The FeLV protein used in the vaccine is not extracted from viruses but is made in a bacterium using ‘recombinant technology’. When a cat is given the vaccine the cat’s immune system recognises the protein as ‘foreign’ and makes antibodies against it. In the future, the immune system will be able to produce antibodies more quickly when it is exposed to FeLV, which will help to protect against the disease caused by the virus.

Leucogen also contains aluminium hydroxide gel and extract of Quillaja saponaria as adjuvants (ingredients that strengthen the immune response).

In one field study kittens aged 8 to 9 weeks were given an initial vaccination course of Leucogen with 2 injections 3 weeks apart and an annual booster injection 1 year later. After the first injection 69% of the kittens had antibodies to FeLV and this increased to 100% after the second injection. Some 64% of cats still had FeLV antibodies before the annual booster, and 100% of cats had FeLV antibodies after the booster.

In a second study, kittens aged 8-9 weeks were given an initial vaccination course of a combination vaccine consisting of one dose of Feligen RCP (against feline rhinotracheitis virus, feline calicivirus and feline panleucopenia virus) with one dose of Leucogen. After the second injection, 100% of kittens had antibodies to FeLV.

A laboratory study in which cats were exposed to feline leukaemia virus confirmed that following the first annual booster vaccination cats were protected for a three year period against leukaemia.

The most common side effects with Leucogen (which may affect up to 1 in 10 cats) are a moderate and short-lived local reaction (<2 cm) after the first injection which resolves without treatment within 3 to 4 weeks, raised body temperature (lasting 1 to 4 days), apathy (listlessness) and digestive disturbances.

Leucogen must not be used in pregnant cats.

For the full list of restrictions and all side effects reported with Leucogen, see the package leaflet.

In case of accidental self-injection, medical advice should be sought immediately and the package leaflet or label shown to the doctor.

The European Medicines Agency decided that Leucogen’s benefits are greater than its risks and it can be authorised for use in the EU.

Leucogen received a marketing authorisation valid throughout the EU for Leucogen on 17 June 2009.