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Fact check: Nasal flu vaccine does not spread flu

Some social media posts have made the false claim that the nasal flu vaccine, also known as flu mist, spreads the flu.

Reuters Fact Check. REUTERS/Axel Schmidt

Examples can be seen here and here .

“3,000,000+ Children in the UK are due to get the Flu Mist,” the post reads.

“Don’t forget, it’s live, you can catch it from them and guess what, so can grandma! This is a LIVE VIRUS they spray into your childs [sic] nose.”

“Flu Mist spreads Flu. This is how they keep the Pharmaceutical companies in business.”

According to Britain's National Health Service, the vaccine for children is a spray that contains live flu viruses that have been weakened so as to stimulate the immune system while not causing disease (here) .

The spray should not, however, be given to children who have a severely weakened immune system, have certain allergies or severe asthma.

The Vaccine Knowledge Project, a website managed by the Oxford Vaccine Group, an academic research group within the University of Oxford, says there is no evidence that healthy unvaccinated people can catch the flu from a vaccinated person (here).

It says that for few days after vaccination, children can shed the virus when they cough or sneeze. However, it adds that the weakened virus does not spread as easily as the natural flu virus that circulates within the population, and it can not grow inside the body. It also advises that the amount of virus shed is normally too low to infect others, and that the virus does not survive for long outside the body.

The Government's 'green book' on immunisation against infectious disease, as per the April 2019 update, contains the following paragraph examining the potential of the Fluenz Tetra® nasal flu spray to spread flu (here

“There is a theoretical potential for transmission of live attenuated influenza virus in Fluenz Tetra® to immunocompromised contacts for one to two weeks following vaccination. In the US, where there has been extensive use of the LAIV (Live Attenuated Influenza Vaccine), there have been no reported instances of illness or infections from the vaccine virus among immunocompromised patients inadvertently exposed. Where close contact with very severely immunocompromised patients (e.g. bone marrow transplant patients requiring isolation) is likely or unavoidable (for example, household members), however, appropriate alternative inactivated influenza vaccines should be considered.”

Rather than spread the flu, Public Health England research suggests that the vaccine has reduced flu in the population. Citing this research, the Vaccine Knowledge project says that across all age groups including children, the flu vaccine prevented 15-52% of flu cases between 2015 and 2020 (tinyurl.com/yy97ks3c ) .

VERDICT

False. The nasal flu vaccine contains live flu viruses that have been weakened so they do not cause flu in others.

This article was produced by the Reuters Fact Check team. Read more about our fact-checking work here.    

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