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Pigs can be used to test human flu vaccines, say Pirbright scientists

Pigs may be a good model for testing seasonal human flu vaccines, suggest findings from the BBSRC-funded Pirbright Institute.

In a paper published in the journal Frontiers in Immunology, a study led by Dr Elma Tchilian, Head of the Mucosal Immunology group at The Pirbright Institute, showed that pigs infected with the 2009 H1N1 swine flu pandemic virus produced lower levels of virus if they had been immunised with the vaccine used during the 2017-18 human influenza season.

Vaccine evaluation is important to ensure they provide the best protection possible against the seasonal burden of influenza, which causes 650,000 deaths per year worldwide (according to the World Health Organization). The traditional vaccine received as an injection into the arm muscle is only 50-60% effective. However, weakened vaccines (known as live attenuated influenza vaccines) can be up to 75-80% effective when inoculated using a nasal spray in children.

The pig respiratory system is comparable to humans, and both pigs and humans can be infected with influenza A virus strains of similar subtypes. Pigs are also more physiologically and anatomically similar to humans than small mammals often used in studying influenza vaccines.

The 2017-18 live attenuated vaccine in the study was administered in a single dose to the nose of the pigs. The vaccine was shown to reduce the amount of H1N1 virus produced in vaccinated pigs, compared to pigs receiving no vaccine before being infected.

In doing the same experiments with a H3N2 virus the scientists were unable to determine the degree of protection from the vaccine because some pigs did not become infected at all. However, their study did show that the H3N2 vaccine component produced a stronger immune response than the H1N1 component. This is in line with human studies, providing further evidence that pigs may be useful for studying human influenza A virus infection.

“The fact that a single dose of a human vaccine induces detectable responses and a reduction in virus production when pigs were subsequently infected with a pandemic H1N1 subtype virus suggests that pigs may be a useful model for assessing seasonal vaccines against influenza A viruses and studying the mechanisms that lead to protection,” said Dr Elma Tchilian.