Flu vaccines play an significant role in protecting against bird flu. But not for the reason you might think

The current strain of highly pathogenic avian influenza, commonly known as bird flu, has become a global problem. This virus has affected many millions birds, some others animal speciesand a small number of people.

Last week the Australian government issued a warning for residents traveling to Europe, North America, South America and Asia about the risk of bird flu.

Alert posted on Smartraveller websiteprovides advice on making sure your flu vaccine is up to date. If you are planning to travel, this usually means you have had a flu vaccine this year, although if it is 3-6 months since your vaccination you should discuss this with your doctor.

But the seasonal flu vaccine we get every year doesn’t actually prevent bird flu in humans. So why is it recommended in this context?

Some facts about bird flu

Smartraveller’s Notes several strains Bird flu viruses are currently circulating.

The most disturbing strain, called clade 2.3.4.4bemerged several years ago from the influenza A (H5 or A/H5) strain that had been circulating for several decades.

Clade 2.3.4.4b primarily affects birds, including wild birds and poultry. It has had devastating effects on bird populations, as well as on farmers and others involved in the poultry industry.

In recent years, clade 2.3.4.4b has adapted to infect some mammalsUnfortunately, it seems to cause grave illness in some animalsSome marine mammals have been particularly tough hit, causing mass mortality events reported in elephant seals and sea lions. Bird flu has also spread to the United States among dairy cows.

Compared to the huge number of cases in animals, a relatively petite number have been reported. people infected with bird fluSince 2003, 878 cases Human cases of A/H5N1 influenza have been reported, with a petite percentage reported after 2020, when clade 2.3.4.4b first appeared. Reported cases have been in people who had close contact with infected animals. The disease does not appear to spread from person to person.

In connection with the risk for travelers is lowThere are situations where the risk may be greater, such as for people visiting livestock markets or people travelling specifically to work with wildlife or in food production.

Infections in humans H5 flu can vary greatly in severity, from bland conjunctivitis to deadly pneumonia. H5 flu strains appear to be sensitive to antiviral drugs (oseltamivir, also known as Tamiflu) and they are generally recommended as a treatment for infections in humans, but this is not clear whether they reduce the risk of death in people with severe disease.

To date, one case of A/H5 influenza (not 2.3.4.4b) has been reported. reported in Australiain a child who has recently returned from abroad.

One sec clade 2.3.4.4b detected on all continents except Australiaother strains of bird flu (A/H7) were reported here earlier this year.

Seasonal flu vaccines are not effective against bird flu

Seasonal flu refers to the strains of flu that circulate each year. Since the COVID-19 pandemic, three different strains have circulated in varying proportions – Influenza A H1N1 (originating from 2009 swine flu strain), influenza A H3N2 (which has in circulation since 1968) and a strain of influenza B. Interestingly, the second strain of influenza B (Yamagata lineage) it seems to have disappeared during the COVID pandemic.

Seasonal flu vaccines contain the current variants of these types (A/H1N1, A/H3N2, and B), which are recommended annually by the World Health Organization. These are moderately effectivereducing the risk of hospitalization by approximately 40–60%.

Flu vaccines are quite specific in the protection they provide. In the case of seasonal vaccines, even very petite changes in the virus from year to year are enough to allow it to “escape” vaccine-induced immunity. That is why seasonal flu vaccines they do not provide any protection against influenza A/H5.

Preventing the emergence of a bird-human hybrid strain

The rationale for recommending influenza vaccination for travellers in the context of the current avian influenza epidemic is that seasonal influenza vaccines may aid reduce the risk of co-infection with an A/H5 strain and a seasonal influenza strain.

When this happens, there is a chance that the genetic code of the two strains of the virus will “recombine.” This could have the ability to carry a seasonal human virus with the severity of a bird flu virus. The 2009 swine flu strain arose from recombination Over the years, several strains have become more contagious to humans.

Of course, a more effective vaccine would include an H5 strain to generate immune responses specific to the H5 influenza strain. Vaccine manufacturers have H5 vaccines have been developed for years, but so far only Finland implemented the H5 vaccine among a petite group of people who work closely with potentially infected animals.

Currently risk level The risk that H5 poses to humans is not considered to be sufficient to require a specific vaccination programme because the potential benefits are petite compared to the costs and potential risks of any novel vaccination programme.

The Value of the Flu Vaccine for Travelers

Seasonal flu vaccines protect against flu infection and can also reduce the risk of simultaneous infection with human and bird flu strains. Bird flu aside, for most travelers who haven’t received a flu shot this year, reducing the risk of their travel plans being disrupted by the disease should be reason enough to get vaccinated.

For people who have already received a flu vaccine this season, as with COVID vaccines, protection appears to be greater after vaccination fade over timeSo if you’re travelling to the Northern Hemisphere during the winter months and it’s been more than 3 to 6 months since your last flu shot, your doctor may recommend you get another one.

Bird flu poses a low risk to most travellers, but people should take sensible precautions, such as avoiding close contact with birds at markets.