Faced with uncertainty about how and when the flu virus might evolve, it’s better to gamble than to be conservative
- Sam Wilks
In a study published in the journal Science, the researchers in the UK, Vietnam, The Netherlands and Australia, led by the University of Cambridge, describe how an immunological phenomenon they refer to as a ‘back boost’ suggests that it may be better to pre-emptively vaccinate against likely future strains than to use a strain already circulating in the human population.
Influenza is a notoriously difficult virus against which to vaccinate. There are many different strains circulating – both in human and animal populations – and these strains themselves evolve rapidly. Yet manufacturers, who need to produce around 350 million doses ahead of the annual ‘flu season’, must know which strain to put in the vaccine months in advance – during which time the circulating viruses can evolve again.
Scientists at the World Health Organisation (WHO) meet each February to select which strain to use in vaccine development. Due to the complexity of human immune responses, this is decided largely through analysis of immune responses in ferrets to infer which strain best matches those currently circulating. However, vaccination campaigns for the following winter flu season usually start in October, by which time the virus may have evolved such that the effectiveness of the vaccine match is reduced.
“It’s a real challenge: the WHO selects a strain of flu using the best information available but is faced with the possibility that the virus will evolve before the flu season,” explains Dr Judy Fonville, one of the primary authors on the paper and a member of WHO Collaborating Centre for Modelling, Evolution and Control of Emerging Infectious Diseases at the University of Cambridge. “Even if it does, though, it’s worth remembering that the flu vaccine still offers much greater protection than having no jab. We’re looking for ways to make an important vaccine even more effective.”
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Image: Flu Vaccination Grippe (cropped)
Credit: Daniel Paquet
Reproduced courtesy of the University of Cambridge
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