Carissa Wong is a person.

Human cells infected with influenza virus

An electron microscope is used to view human cells.

Steve Gessner is a science writer.

Hopes for a universal flu vaccine have been raised by the results of an experimental vaccine in animal testing.

Influenzaviruses are a moving target for vaccine developers. Each year the flu vaccines are tailored to give immunity against certain strains. The vaccine is less effective in certain years due to the fact that researchers get the prediction wrong.

A universal flu vaccine is said to be effective against all flu strains. No universal vaccine has yet gained approval for wider use, even though researchers have tried to achieve this by making vaccines that are common to several strains of flu.

The Pfizer/BioNTech and Moderna covid-19 vaccines were the first to use the same approach to create a vaccine.

Just like DNA, there are genetic codes in mRNA. There are 20 known strains of Influenza A and B, and the vaccine contains fragments of them.

The strains have different versions of the haemagglutinin and neuraminidase on their surface. The universal vaccine won't match every possible variant because there can be slight variations in the H1N1 strain.

In tests on mice, the team found that the animals had a stable level of anti-flu antibodies for up to four months.

The team gave a universal flu vaccine or a dummy vaccine to mice. One variant of the H1N1 flu virus was similar to the one in the vaccine, but the other variant was different.

Eighty per cent of the mice that were given the flu vaccine survived being exposed to the more distinct variant of the flu vaccine. All of the mice that received the dummy vaccine died within a week of being exposed to either variant.

A group of mice were given a vaccine that only targets the flu strain they were exposed to, and all of them survived over the course of a year. Albert Osterhaus at the University of Veterinary Medicine Hannover in Germany, who wasn't involved in the study, said the universal flu vaccine would offer less protection against new flu strains than an annual vaccine matched to new flu strains.

The vaccine was tested in ferrets.

The mice and ferrets are as good as animal models. Peter Palese is a professor of medicine at the Icahn School of Medicine at Mount Sinai.

Palese says that a key benefit of mRNA vaccines is that they can easily be scaled up compared with other approaches.

If longevity of immunity in humans is confirmed, this strategy could be an option.

The data from the animals are promising and merit further study. It is difficult to predict what the clinical data will bring with previous studies of universal flu vaccines.

The vaccine tested in ferrets may hold promise for protecting against future flu strains against severe disease in humans.

The journal's title is "science."

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