Flu viruses come in many forms (Picture: Getty/Science Photo Libra)
A flu virus that infected millions and targeted children has disappeared off the face of the Earth – and experts are so sure it’s gone, they think it should be removed from vaccines.
The now-extinct viruses belonged to the influenza B family tree known as the Yamagata lineage.
Never heard of it? Not surprising – but you might have had it.
It is one of four commonly included in annual influenza vaccinations, but went conspicuously quiet in March 2020 – around the time the whole world went into lockdown.
As Covid-19 ran riot, precautions taken to stop the spread of the disease such as masks and social distancing drove flu cases to historic lows, to the point one was eradicated one completely.
Yamagata is one of two ‘B’ flu viruses, alongside Victoria. The two split apart in the 1980s, but remain closely related.
However, as the category suggests, they are not the most deadly, nor fastest evolving viruses on the scene – and because they evolve slowly, immunity typically last longer, mean adults are less susceptible. ‘B’ viruses tend to cause more illness in children, who have not been exposed to them as much.
Children tend to pick up ‘B’ flu infections more than adults (Picture: Getty)
Meanwhile, it is ‘A’ flu viruses, such as the familiar H1N1, that are generally of more concern, and are the types to cause pandemics, such as the ‘great flu’ of 1918, which killed an estimated 50 million people.
No ‘B’ virus is known to have caused a pandemic, and with Yamagata apparently off the scene, the US Food and Drug Administration (FDA) has agreed with the World Health Organisation (WHO) that it no longer needs to be included in seasonal flu vaccines.
‘In the interest of public health, FDA strongly recommended to influenza vaccine manufacturers the removal of the B/Yamagata lineage virus from seasonal influenza vaccines in the US for the 2024-2025 influenza season,’ the administration said.
The influenza vaccine currently tackles four viruses (Picture: Getty/Science Photo Libra)
‘FDA and the manufacturers have been working together so that the move from quadrivalent to trivalent seasonal influenza vaccines occurs for the upcoming influenza season.’
The past decade has seen US flu vaccines protect against four types of flu, two influenza A strains and two influenza B strains. Now that number will be three.
In return, it is hoped manufacturers can increase their production capacity, making more doses.
‘We don’t want to vaccinate you for a virus that’s no longer in circulation for three, four years now,’ said Dr Hana El Sahly, chair of the FDA advisory committee.
However, despite health experts agreeing to get rid of the strain in flu vaccines, people in the pharmaceutical industry argued that manufacturers would need time to switch to the new formula.
In November 2023, the Government’s Green Book also stated that trivalent vaccines were clinically suitable.