I keep hearing I should get a flu shot to help prevent bird flu — but I thought flu shots only prevented illness from the particular strains the shot was designed for. Does getting a traditional flu shot do anything to prevent bird flu transmission?
Former influenza epidemiologist here and the answer is probably not. Our current influenza vaccines in the US (and in almost all countries) are trivalent, meaning they have 3 strains: an influenza A H1N1 (aka swine flu), an influenza A H3N2, and an influenza B (Victoria). Fun fact, they used to include 4 strains, but COVID actually wiped out the second B strain and it hasn’t been detected since 2020.
Unfortunately, the current bird flu is H5, a separate influenza A strain. Typically there isn’t a lot of shared clinical protection overlap between genomes this different. This is why influenza vaccines typically use 3 (and formerly 4) different strains of the virus, to confer the most protection.
However, unless you work in dairy or poultry, I would not worry. I am not particularly worried. I know it’s making headlines, but only 66 human cases are in the US so far, and all but 2 had direct contact with those animals. Currently there is no documented person-to-person transmission and certainly nothing like what we saw early on with COVID.
If you want my personal take, I still mask at large events / crowded places / airplanes to avoid flu and COVID altogether. I still encourage everyone who is ill to mask and stay home, even though it’s out of fashion. I think we will see egg, dairy, poultry, and beef prices rise with H5, as farmers are forced to cull animals. Also, we may see cases from raw milk and backyard animal husbandry - please don’t drink raw milk, pet cows, kiss chickens, touch dead birds without gloves, etc. right now and you probably won’t get bird flu.
Hope that helps, happy to answer any other influenza or respiratory infectious disease Qs!
Edited to add: The fact we have human cases at all is because farm workers - usually immigrants with limited English - are routinely exploited, denied PPE, or put at risk in unacceptable ways. Farms are basically self regulated in the US, though they are officially regulated by the USDA. It is extraordinarily difficult to get farms to cooperate with pandemic preparedness. You have to pay them federal money to do anything. There have been documented cases of farm workers being told to cull infected birds with zero PPE, and that’s unacceptable. These vulnerable people are the ones paying the price for our H5 knowledge right now, and it’s not right. It’s disheartening to have worked on pandemic preparedness for decades, fumble COVID altogether, and still fail to prepare for the next one. As climate change continues unmitigated we expect to see more human-wildlife interaction and more zoonotic diseases. We can’t just do good science; we also must address workers’ rights, capitalism, and climate change.
won’t there be some limited immunity against H5N1 from N1 part? also regular seasonal flu vaccination should prevent antigenic shift because coinfection is less likely, i think it’s a part of advice for high risk farm workers
That’s a very interesting question. @cleanandsunny (or does lemmy use the tag
u/cleanandsunny ?) do you know if the immune system can recognize a portion of the H section or N section of the protein, or instead does it specifically only recognize the HN protein in it’s joined shape?Okay, re: any cross-protection from vaccines, the answer is again likely no. For years people have been working on a “universal vaccine” so we wouldn’t have to do annual shots. There is currently work being done with the mRNA technology that came out of COVID, as well as universal HA targets. But we are, for the moment, still stuck with traditional flu vaccines.
Our current flu vaccines work by stimulating the production of antibodies targeting two surface proteins of the flu virus, HA and NA. These control viral attachment/fusion and release, respectively, which are important for viral infection and replication. When we think about vaccine effectiveness studies we want to see those HA and NA titres high because they are linked with protection.
The human vs avian strains of influenza behave differently when it comes to these proteins. HA proteins of human-to-human strains recognize α(2,6)-linked sialic acid, while avian strains use α(2,3)-linked sialic acid. Not every species has tissues with both of these sialic acid receptors. Some do - like pigs, quails, and turkeys - which is where we see viruses start to shift and cause problems for humans. So, mutations in those HA proteins in avian influenza is what decides whether they can reproduce in humans.
In other words - our current swine flu “H1” vaccine is unable to target any avian flu “H1” protein, and that’s actually a good thing! It means that the strains are well and truly separate, and avian influenzas cannot readily reproduce in humans without additional mutation. If and when we start to see human-to-human transmission of H5, then we can look at that strain’s protein structures and determine appropriate targets for vaccination.
