The European Medicines Agency (EMA) has recommended the authorisation of the first veterinary vaccine in the EU using RNA technology, designed to protect cats against five common infectious diseases, including feline leukaemia virus (FeLV).

FeLV suppresses the immune system and is a common cause of cancer in cats. The virus spreads mainly through close contact between cats, weakening the immune system and potentially leading to blood disorders and other serious infections.

“Nearly 4% of cats in North America alone are affected by this disease [FeLV], a notable percentage when there have been guidelines for prevention in place for decades,” said Meg Conlon, Executive Director for Merck Animal Health, who developed the vaccine.

The vaccine Nobivac NXT HCPChFelV protects against feline herpesvirus, feline calicivirus, feline panleukopenia virus, Chlamydia felis and FeLV. It contains live attenuated forms of four of these pathogens to train the immune system to recognise them. For FeLV, researchers used pieces of FeLV RNA packaged inside a viral particle, a strategy similar to the mRNA Covid-19 vaccines, to deliver instructions that make cells temporarily produce a FeLV protein, triggering an immune response that prepares the body for future exposure to the virus.

To evaluate the vaccine, EMA’s veterinary medicines committee reviewed data from 15 laboratory studies in research cats, in which vaccinated animals were later exposed to the viruses to assess the vaccine’s safety, dosage and effectiveness. This was followed by a field study involving 142 cats under normal everyday conditions. 

Both studies showed that vaccinated cats developed protection against all five infections, with immunity beginning about one week after vaccination, and that the vaccine was generally well-tolerated.