Not as long term but there is an increase in the number of heart attacks and strokes in the weeks after influenza. The body generates an immune response which can result in widespread inflammation that may be involved in this process.

Back in 1945, the push for the flu vaccine was similar to what we are seeing with the SARS-CoV-2 vaccine today. In 1918, the world was hit with a massive influenza pandemic that killed more than 20 million people world wide. By 1945, we had an influenza (H1N1) vaccine available for the general public. Unfortunately, the flu is a rapidly mutating virus, meaning that we see various strains dominating each year and some can turn into pandemics. All we can do is try to predict which strains will be prevalent and vaccinate against those in a yearly vaccine. In short, the answer to your question is that there has been a global push for influenza vaccination in the past, put there isn't currently a push on the level of SARS-CoV-2 vaccination because we haven't seen a flu pandemic on the level with COVID-19 since 1918.

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 ).

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Influenza is a tricky virus to vaccinate against because it rapidly mutates and has multiple strains circulating in one year. Our ability to predict these strains is improving, but it is still a prediction. We are improving the number of strains we can vaccinate against. The first influenza vaccine only vaccinated against H1N1, where as this years influenza vaccine protects against 4 strains.

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/ ).

Symptom wise, the flu tends to give a higher temperature (greater than 38 C or 100.4 F.). Colds usually start with a sore throat and have more nasal symptoms, head ache is common and there may be a cough. Flu has more muscle aches, non productive cough and that higher temperature. Since some of the symptoms overlap, there may be confusion in determining what a person has.

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.

The influenza vaccine is a trade off, like many things in our life. Scientists try to predict the strains that most people will be exposed to during the flu season and put those into the vaccine. For each strain added, we increase the cost of production and more importantly, each strain increases the load on your immune system. More strains might result in multiple shots needed, which decreases the number of people who get fully vaccinated. Or it could cause side effects, similar to what we have seen with the SARS-CoV-2 vaccine, which will decrease the number of people who get the yearly vaccine. Luckily, scientists are working on a universal influenza vaccine. This type of vaccine would vaccinate against a protein on the influenza virus that doesn't change. This would mean protection from more strains, as well as less frequent vaccination.

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.

The current influenza vaccines vaccinate against the active binding sight (head) of the hemagglutinin. This is on of the the spots that mutates every year. The universal influenza vaccine vaccinates against the stalk of the hemagglutinin. This portion of the virus does not rapidly change. There are a number of universal vaccines in clinical trials. These clinical trials ensure the vaccine is effective and safe before it reaches the market. If the vaccines that are currently in clinical trials meet the high standards, we might see a universal flu vaccine in the near future.

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.

>It's totally possible! Scientists have been working on this for years and have some promising candidates being tested in humans right now. Below is some more information that I compiled for another question and here is a good article on one of the universal flu vaccines.
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>The current influenza vaccines vaccinate against the active binding sight (head) of the hemagglutinin. This is on of the the spots that mutates every year. The
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>universal influenza vaccine vaccinates against the stalk of the hemagglutinin. This portion of the virus does not rapidly change. There are a number of universal vaccines in clinical trials. These clinical trials ensure the vaccine is effective and safe before it reaches the market. If the vaccines that are currently in clinical trials meet the high standards, we might see a universal flu vaccine in the near future.

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
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>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/ .

In response to your second question, I do not know of any positive purpose the influenza virus serves on an individual person basis. Historically, the 1918 influenza pandemic may have helped bring WWI to a close, at the cost of many lives. The flu hit the front lines across Europe in the first wave of infection. Influenza weakened and cut the numbers of fighting forces, leading to a need for more diplomatic tactics. I am not sure this is exactly a positive outcome because millions of people died from complications related to the flu, but it did help end a global war.

Besides getting a flu shot, wash, wash and wash the hands. I wear a mask in enclosed spaces (I am older and at higher risk for a "Bad" outcome). Since you can spread the virus before you have symptoms, I don't want to feel responsible for getting family or friends sick. Especially since I have family with health issues.

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.

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.

Unfortunately, as we are seeing this year, the flu did not disappear. The measures taken to prevent COVID-19, such as masking, hand washing and social distancing, are also great ways to prevent influenza. Additionally, during the 2020-2021 flu season, arecord number of influenza vaccines were distributed. Throughout history, it is common to see a decrease in a disease with the rise of another disease. Historiansrefer to these as disease cycles and they have had major impacts on human history.

We already have influenza tests! If you go to a doctors office presenting with Flu-like symptoms, they will likely run a test for influenza. The rapid tests, most commonly found in urgent cares, take about 10-15min and are 90-95% accurate. There is also an RT-PCR test that is very sensitive in detecting viral RNA, but takes more time. There are also Rapid Influenza Diagnostic Tests that are antigen based. These can be done at home, similar to the COVID-19 home test, but their accuracy is lower (50-70% accuracy).

The 1918 influenza is called the H1N1 strain and it is still around today. The flu differs from COVID-19 in one big way. Influenza virus mutates very quickly, which is why we need a new vaccine yearly that covers for different strains. Luckily with Influenza, you can get some protection against similar strains because the mutations are usually small changes. SARS-CoV-2, on the other hand does mutate, but not as rapidly. We don't yet know how our immune systems are going to respond to different strains of SARS-CoV-2. There is some evidence that previous infection with omicron can protect against other variants, but this is still under investigation.

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

Encourage them to do a home Covid test. Get a result in 15 minutes. Of course, the PCR test is more accurate but that is not as easy to do. The diseases have symptoms that can overlap so it is dependent on the person's presentation. There are many online symptom charts comparing Covid, Flu and Cold symptoms.

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.

>Spidersandbeavers · 7 hr. ago
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>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 ).

Myocarditis, or inflammation of the heart muscle, can be caused by a number of viruses. When an infection is identified in the body, the immune system triggers an inflammatory response. Similar to a fire alarm, it is a signal to the body that something is wrong. This can be dangerous when it occurs in the heart because it prevents blood from being pumped. The influenza vaccine, however is not delivered to the heart. The immune inflammatory alarm will be triggered either in the muscle or nose where the vaccine is delivered. Swelling at the injection site is a common side effect, but inflammation of the heart is not. The Mayo Clinic promotes vaccination for those with heart conditions, because if you have a heart condition, you are at increased risk of myocarditis following an influenza infection.

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.

The flu can be spread by individual who have virus but haven't developed symptoms yet. The big difference in symptoms for the flu and the "common" cold is running a higher fever. Colds tend to have fevers that are less than 100.4F while the flu generally goes higher. Colds usually start with a sore throat and then develop nasal symptoms. Individuals with the flu tend to have moderate to severe fatigue. Since there can be overlap of symptoms between the illnesses and can vary from person to person, it can be confusing. The most common difference is usually that higher temperature in the flu.

There are many mutations of the virus and the one that you get may not be the same one that is covered by the vaccine for that year. However, there is some evidence that even if it is not an exact match, people who are vaccinated are better able to fight it and have milder symptoms.

>Average_Cat_Lover · 2 hr. ago
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>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.

>Letspostsomething · 9 min. ago
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>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.

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/ ).

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.

We have known for a while that influenza can transmit via surfaces. We call this fomite transmission. For example, if a person sneezes or coughs onto a desk and then another person touches the desk then rubs their eyes, it is possible to get the flu. This risk is fairly low (4.2% of infections in a 2018 study), but the risk is believed to be even lower for SARS-CoV-2.

>scheisskopf53 · 3 hr. ago
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>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/ .

Interesting question: The viruses are in those areas. When individuals are tested for the antibodies, levels are found in many children. Public health resources are not as available and testing/reporting limited. It simply isn't as reported. Also, malaria is prevalent in many areas and symptoms may be attributed to that wide spread (Africa) disease. I would also guess that better climate leads to less time in enclosed spaces and less opportunity for virus to spread.

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

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

There is still a lot unknown about SARS-CoV-2 because it is a new virus. The flu and COVID-19 have similar symptoms, but they are caused by very different viruses, meaning our immune systems respond differently. We cannot use the flu as a model for things like seasonal effects, because we have seen that COVID-19 is not as strongly linked with seasons as the Flu is. We also know that they both spread through liquid droplets, but influenza is able to spread surface to surface better than SARS-CoV-2. I wish we could use Influenza as a model for SARS-CoV-2 because it would have let us get a grasp on the disease much faster, but unfortunately they are totally different viruses and act differently.