I work in a laboratory at CDC where I need to take showers and wash my hair every time I leave the lab (BSL3 with risk-based enhancements, you can read more about it at https://www.cdc.gov/cpr/infographics/biosafety.htm ), which means I walk around a lot with wet hair, so I have thought about this question too. 😊 Because flu is caused by a respiratory virus (and not wet hair!), the most important thing I do to protect myself from influenza by getting a flu vaccine every year.

>Average_Cat_Lover · 2 hr. ago
>
>How is the development of flu vaccines administered via others ways (nasal spray, droplet) going? Is there a significant difference in vaccine technology used (eg: deactivated virus, egg protein) between them and the normal vaccine?

There are several types of FDA-approved influenza virus vaccines in the US (summarized at https://www.cdc.gov/flu/prevent/different-flu-vaccines.htm ). Advances in influenza virus vaccine technology are ongoing (summarized at https://www.cdc.gov/flu/prevent/advances.htm#vaccine-advances ). Different vaccine formulations have different properties (e.g. egg protein vs egg-free, inactivated vs live-attenuated, etc). While the unadjuvanted, inactivated, intramuscularly-administered influenza vaccine is most common, there are a range of FDA-approved influenza virus vaccines against seasonal influenza viruses.

>Spidersandbeavers · 7 hr. ago
>
>How much more dangerous is flu for kids than covid? What about young adults? Where is the inflection point in age where covid becomes more dangerous? What about when vaccination is factored in (I.e. difference in danger from covid for a vaccinated 65 year old vs. Flu for that same person)?

Influenza can be a dangerous infection for any person at any age. However, there are some populations (based on age, vaccination status, and/or underlying health conditions) for which increased likelihood of increased disease severity is possible (https://www.cdc.gov/flu/highrisk/index.htm). This is why annual flu vaccination is suggested for everyone six months of age or older with few exceptions (see https://www.cdc.gov/flu/prevent/vaccinations.htm ).

More information on recent flu vaccine advancements is available here: https://www.cdc.gov/flu/prevent/advances.htm . The goal is always to minimize the amount of time it takes from identifying a novel strain circulating among humans, to having a safe and effective vaccine against that virus. One of the ways we try to achieve this is preparing candidate vaccine viruses (CVVs) against zoonotic influenza viruses that are considered to have pandemic potential (the process is described at https://www.cdc.gov/flu/avianflu/candidate-vaccine-virus.htm ). CDC and other agencies have prepared a wide range of CVV’s that could rapidly be employed for manufacturing vaccine for human use if needed.

The quadrivalent inactivated influenza vaccine is targeted against currently circulating H1N1 and H3N2 influenza A viruses, and Yamagata and Victoria lineage influenza B viruses (4 circulating types of virus = 4 components of the vaccine). Universal vaccine approaches (as we’ve mentioned in responses to other questions in this session) are hoping to expand vaccine breadth not by including more individual HA targets, but by targeting conserved parts of the virus that are consistent across a wide range of virus subtypes.

>scheisskopf53 · 3 hr. ago
>
>When I was in primary school, my perfectly healthy friend lost his eyesight almost completely over a week or so. He does see vague shapes but is legally blind. Back then, the adults told me that it was due to flu complications. Is this actually possible? If so, what would be the mechanism?

I am not a medical doctor and cannot speak to your friend’s situation. On the larger question of how influenza virus infection may interact with the eyes, this is an area I study frequently in the laboratory. Some influenza viruses are able to replicate specifically within ocular tissue (because the same types of receptors that influenza viruses bind to in the respiratory tract are also present on the human ocular surface) and influenza viruses can use the eye as a portal of entry to establish a respiratory infection (because the lacrimal duct bridges ocular and respiratory tissues). You can read more about documented cases of ocular complications following influenza virus infection and how we study this in the laboratory here: https://pubmed.ncbi.nlm.nih.gov/29477464/ .

>Letspostsomething · 9 min. ago
>
>Why don’t we just create a shot with with all the H’s and N’s in it rather than creating different shots each year?

There are many different types of universal vaccine approaches under development; many of them target conserved parts of the virus (in other words, part of the virus that stay the same for long periods of time, and are consistent between different HA and NA subtypes). Many of these approaches are reviewed here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028071/ By targeting parts of the virus that do not change (unlike the current inactivated influenza vaccines, which target parts of the virus that do a good job stimulating immune responses but are more likely to change from year to year), universal vaccines hope to have broader efficacy against different virus subtypes.

At this time, CDC is participating in a broad inter-agency partnership coordinated by BARDA (https://www.phe.gov/Preparedness/planning/nivms/Pages/default.aspx ) that supports the advanced development of new and better flu vaccines. These efforts already have yielded important successes (https://www.cdc.gov/flu/prevent/advances.htm#vaccine-advances ). Part of this effort is the eventual development of a “universal vaccine” that would offer better, broader and longer-lasting protection against seasonal influenza viruses as well as novel influenza viruses. This task poses an enormous scientific and programmatic challenge, but a number of government agencies and private companies already have begun work to advance development of a universal flu vaccine.

>piercet_3dPrint · 3 hr. ago
>
>Where does Influenza "go" in between flu seasons? Is it just slowly working its way around the planet and just takes about a year to make the journey? or does it basically go infect something else until conditions are ideal for us to get infected again? Or is it there the whole time usually and we are just more prone to getting it at certain times of the year?

Influenza is always circulating among humans, just in different locations at different times. For example, the flu season in the US is primarily between Oct-May, whereas in Australia, the flu season is primarily during their winter months. There are other geographic locations where there are multiple ‘seasons’ during a year (for example, in Africa: https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-022-07727-2 ). There are lots of different factors which contribute to seasonality of respiratory viruses, such as influenza, some of which are discussed here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2656132/ .

RNA-based influenza vaccines offer several advantages over current inactivated influenza vaccines (such as reduced production times, elimination of egg- and cell-based propagation steps, and the potential for rapid updating in the event of antigenic drift). There are numerous different mRNA-based influenza vaccines in development, with phase 1 clinical trials reported for some (such as https://pubmed.ncbi.nlm.nih.gov/31079849/ ). More information on recent flu vaccine advancements is available here: https://www.cdc.gov/flu/prevent/advances.htm

The first and best way to protect yourself and your family from flu is to get an annual flu vaccine (https://www.cdc.gov/flu/prevent/vaccinations.htm). There are also everyday preventive actions you can take, like avoiding people who are sick, staying home when you are sick, covering your coughs and sneezes, and washing your hands for at least 20 seconds with soap and water (https://www.cdc.gov/flu/prevent/prevention.htm). You can also consider wearing a well-fitting mask which may help reduce the spread of respiratory viruses. Finally, it’s important to know that if you do get sick with flu, there are prescription antiviral drugs (https://www.cdc.gov/flu/treatment/treatment.htm) that can be used to treat your flu illness. Treatment works best if started within 2 days of illness onset. However, starting them later can still be helpful, especially if the sick person has a higher-risk health condition or is very sick from flu (for example, hospitalized patients). Follow your doctor’s instructions for taking these drugs.

At this time, CDC is participating in a broad inter-agency partnership coordinated by BARDA (https://www.phe.gov/Preparedness/planning/nivms/Pages/default.aspx) that supports the advanced development of new and better flu vaccines. These efforts already have yielded important successes (https://www.cdc.gov/flu/prevent/advances.htm#vaccine-advances). Part of this effort is the eventual development of a “universal vaccine” that would offer better, broader and longer-lasting protection against seasonal influenza viruses as well as novel influenza viruses. This task poses an enormous scientific and programmatic challenge, but a number of government agencies and private companies already have begun work to advance development of a universal flu vaccine.

Development of universal vaccines represents an area of ongoing, active research (see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028071/ ). The goal of these vaccine approaches is to both expand the protective scope (e.g. protecting against a broader range of influenza viruses) and extend the protective duration (e.g. not needing an updated vaccination every flu season). One of the primary reasons a new flu shot is formulated every influenza season is that influenza viruses circulating in humans are constantly changing (termed ‘antigenic drift’ (read more at: https://www.cdc.gov/flu/about/viruses/change.htm ). Because our current inactivated influenza vaccines are targeted against parts of the virus that are most prone to change over time, yearly vaccination with updated flu shots ensures that you can develop protective immune responses against the most currently circulating strains possible.

Due to a process called ‘antigenic drift’, influenza viruses are constantly changing as they circulate within a population (read more at: https://www.cdc.gov/flu/about/viruses/change.htm ). The standard inactivated influenza vaccine includes multiple different subtypes of virus (from H1N1, H3N2, and influenza B viruses) and each component can change in this manner. And yes, due to manufacturing timelines, the decision of which specific virus to include in the vaccine takes place months before you actually receive the vaccine in a clinic (see Figure 1 in this publication for an example of the timeline: https://onlinelibrary.wiley.com/doi/full/10.1111/irv.12383 ). There are intense efforts underway trying to move towards ‘universal’ influenza vaccines (in other words, targeting parts of the influenza virus in the vaccine that are not subjected to antigenic drift), though this approach represents a challenging undertaking for several reasons (summarized in https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028071/ ).

Influenza (flu) and the common cold are both contagious respiratory illnesses, but they are caused by different viruses. Flu is caused by influenza viruses only, whereas the common cold can be caused by a number of different viruses, including rhinoviruses, parainfluenza, and seasonal coronaviruses (https://www.cdc.gov/coronavirus/general-information.html). Seasonal coronaviruses should not be confused with SARS-CoV-2, the virus that causes COVID-19 (https://www.cdc.gov/coronavirus/2019-ncov/index.html).

Because flu and the common cold have similar symptoms, it can be difficult to tell the difference between them based on symptoms alone. In general, flu is worse than the common cold, and symptoms are typically more intense and begin more abruptly. Colds are usually milder than flu. People with colds are more likely to have a runny or stuffy nose than people who have flu. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations. Flu can have serious associated complications (https://www.cdc.gov/flu/symptoms/symptoms.htm). There are multiple respiratory viruses in circulation right now (https://www.cdc.gov/media/releases/2022/t1104-update-respiratory-disease-circulation.html), so, your doctor may test you to determine which treatment is right for you. If you do get sick with flu, prescription flu antivirals can help treat your illness, and can make your illness milder and shorten the time you are sick.

The best way to protect yourself from is to get an annual flu vaccine. There are also everyday preventive actions (https://www.cdc.gov/flu/prevent/prevention.htm) you can take, like avoiding people who are sick, staying home when you are sick, covering your coughs and sneezes, and washing your hands for at least 20 seconds with soap and water. You can also consider wearing a well-fitting mask which may help reduce the spread of respiratory viruses. This might be especially useful in certain circumstances, for example, in household settings when someone is sick or in crowded community settings for people at higher risk when respiratory disease activity is high.

With few exceptions, influenza vaccines are recommended for everyone 6 months and older (see https://www.cdc.gov/flu/prevent/vaccinations.htm ). However, vaccination rates vary between countries, and can vary at country level between different age groups and risk groups. For example, less resourced countries may have limited vaccine available; even when vaccine is available, there are several factors which can contribute to low vaccination use (summarized here: https://www.who.int/europe/news-room/fact-sheets/item/influenza-vaccination-coverage-and-effectiveness ).

You cannot tell the difference between flu and COVID-19 by symptoms alone because some of the symptoms are the same. Some tests can differentiate between flu and COVID-19 at the same time. If one of these tests is not available, many testing locations (https://www.hhs.gov/coronavirus/community-based-testing-sites/index.html) provide flu and COVID-19 tests separately. Talk to a healthcare provider about getting tested for both flu and COVID-19 if you have symptoms. Learn more: https://www.cdc.gov/flu/symptoms/flu-vs-covid19.htm

In order to know how prevalent different influenza viruses are in different locations, we need to conduct surveillance, and how much active surveillance of influenza viruses is taking place can vary greatly between different locations (as an example, this MMWR report discussed differences in influenza activity worldwide during 2018: https://pubmed.ncbi.nlm.nih.gov/30359347/ ). The WHO’s Global Influenza Surveillance and Response System (GISRS) aggregates data from different influenza virus surveillance systems worldwide to better understand which viruses are circulating where and to what degree (more info of CDC’s role in GISRS is: https://www.cdc.gov/flu/weekly/who-collaboration.htm ). Thinking about a continent like Africa, there is still circulation of influenza viruses, but seasonality can vary depending where you look (described more in this 2022 research paper: https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-022-07727-2 ).

RNA-based influenza vaccines offer several advantages over current inactivated influenza vaccines (such as reduced production times, elimination of egg- and cell-based propagation steps, and the potential for rapid updating in the event of antigenic drift). There are numerous different mRNA-based influenza vaccines in development, with phase 1 clinical trials reported for some (such as https://pubmed.ncbi.nlm.nih.gov/31079849/ ). More information on recent flu vaccine advancements is available here: https://www.cdc.gov/flu/prevent/advances.htm

Influenza A (H1N1 and H3N2) and Influenza B (Yamagata and Victoria lineages) have circulated in humans for many years; a paucity of official reports of Influenza B Yamagata lineage virus infection in humans since 2020 supports that this lineage is not currently circulating at a high level among humans (you can read more about how these different viruses vary at https://www.cdc.gov/flu/about/viruses/types.htm ). Influenza viruses and SARS-CoV-2 both spread primarily by the respiratory route, and so many nonpharmaceutical measures taken to reduce the spread of COVID-19 (like wearing masks, increased social distancing, etc) also led to reduced circulation of influenza viruses during the pandemic (see more https://pubmed.ncbi.nlm.nih.gov/34292924/ ).

The exact composition of seasonal influenza vaccines is decided semiannually (for vaccines prepared for use during flu season in the northern hemisphere, and then again for use in the southern hemisphere, because their flu seasons happen at different times). Once that decision is made (in collaboration by the WHO and various national authorities), it is very difficult to ‘update’ the vaccine composition due to tight manufacturing deadlines associated with producing sufficient quantities of inactivated vaccine for widespread use. This is why influenza virus surveillance year-round, world-wide, is so important: it gives the subject matter experts who make decisions about choosing specific candidate vaccine viruses the most information possible to make evidence-based decisions regarding vaccine composition that will be a close a match to circulating viruses during flu seasons as possible.