Study didn’t link children’s flu vaccine to strep A infections

21 December 2022
What was claimed

A study published in 2014 showed a connection between children’s nasal flu vaccines and strep A infections.

Our verdict

The study, which was carried out in mice, looked at streptococcus pneumoniae, not strep A. It also found that nasal flu vaccines did not increase the risk of severe infections.

A post on Facebook wrongly claims that an “article published by Pub med [sic] from 2014 [...] connected the kids flu nasal spray to increased risk of strep A”. 

The article in question—a study published in the scientific journal mBio—is linked to in the comments section by the author of the post. 

This study has been shared widely as alleged evidence that the nasal flu vaccine given to children can cause strep A infections.

However, as we have written before, the 2014 study does not show a link between the flu vaccines and strep A infections. 

Strep A is a bacteria that usually causes mild illnesses such as a sore throat. In some cases it can cause scarlet fever, which is usually mild.

The bacteria can also cause more serious and even life-threatening infections called invasive group A strep infections when the bacteria enters deeper into the body, such as in the lungs or the bloodstream. These infections have killed 16 children in England since September,  according to the UK Health Security Agency (UKHSA), with further reports of three other deaths in Wales and Northern Ireland

The study mentioned in the Facebook post found that the live attenuated flu vaccine (the same type given to children in the UK) increases the likelihood of finding two types of bacteria—including two strains of streptococcus pneumoniae—in the upper respiratory tract of mice. 

This doesn’t mean that the nasal flu vaccine leaves children more susceptible to strep A infections. Despite sounding similar, streptococcus pneumoniae and strep A (group A streptococcus) are different types of bacteria. 

Streptococcus pneumoniae is the name given to a group of more than 90 different strains of bacteria which can cause non-invasive infections such as bronchitis, as well as invasive infections such as pneumonia and meningitis. The study looked at two of these strains, and did not find any evidence of an increased risk of severe infection or death caused by streptococcus pneumoniae in mice given the vaccine.

The study also highlights that while flu vaccination with live attenuated vaccines “primes the upper respiratory tract for increased bacterial growth and persistence of bacterial carriage” in a very similar way to an actual flu virus infection [sometimes referred to as wild-type influenza], it doesn’t increase severe bacterial disease in the lower respiratory tract in the way an actual flu virus infection can.

Dr Simon Clarke, associate professor in cellular microbiology at the University of Reading told Full Fact earlier this month: “When you get flu, often what kills you [...] is a bacterial infection further down in your lungs. So you don't get that with the vaccine, but you do with wild type flu.” 

New pre-print research from the UKHSA found a reduction in strep A infections in areas where more children received the nasal flu vaccine, though it said “there was no difference in scarlet fever or invasive group A strep (iGAS) notifications.”.

A UKHSA spokesperson told Full Fact: “The flu vaccine reduces the risk of having flu and group A Strep infections at the same time therefore it reduces the chance of developing invasive Group A Strep.

“We strongly recommend children who are eligible get a flu vaccine – it’s the best way to protect them from serious illness. The flu vaccine for children has an excellent safety record, this includes the nasal spray given to school aged children and pre-schoolers, which has been given to millions of children in the UK and worldwide.”

We have seen a large number of posts featuring misleading information about strep A in recent weeks, including false claims that nasal flu vaccines directly contain the bacteria and that infections can be treated with homeopathic remedies instead of the necessary antibiotics. 

Image courtesy of Vitolda Klein

Full Fact fights bad information

Bad information ruins lives. It promotes hate, damages people’s health, and hurts democracy. You deserve better.