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The Flu Vaccine Works

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Last Updated: 02 July 2021

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General | Latest Info

Everyone over the age of 6 months should get a flu shot each year in order to protect against influenza. This is different from many immunizations, which may only require shot once or twice in a lifetime. This is because there are many strains of flu virus, and those circulating change with each flu season. While you may have had flu in the past, your immune system may not have yet confronted the version of the virus that may lead to infection this year. If there are viruses circulating that are not covered by Vaccine, you may still get flu even if you had Flu shot. The good news is that antibodies your body produces to fight viruses in Flu shot are typically able to provide some resistance to mutated versions of that virus. Even if it does not prevent illness, you are more likely to have less severe case of illness if you have had Flu shot.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Continued

Flu season will look different this year, as the country grapples with a coronavirus pandemic that has killed more than 172 000 people. Many Americans are reluctant to visit doctors Office and public health officials worry people will shy away from being immunize. Although sometimes incorrectly regarded as just another bad cold, flu also kills tens of thousands of people in the US each year, with very young, elderly and those with underlying conditions most vulnerable. When coupled with the effects of COVID - 19, public health experts say it is more important than ever to get flu shot. If enough of the US population get vaccinated, more than 45% of WHO do last Flu season, it could help head off nightmare scenario in the coming winter of hospitals stuff with both COVID - 19 patients and those suffering from severe effects of Influenza. Aside from the potential burden on hospitals, there is possibility people could get both viruses and no one knows what will happen if you get Influenza and COVID because it has never happened before, Dr. Rachel Levine, Pennsylvania Secretary of Health, told reporters this month. In response, manufacturers are producing more vaccine supplies this year, between 194 million and 198 million doses, or about 20 million more than they distributed last season, according to the Centers for Disease Control and Prevention. As flu season approaches, here are some answers to a few common questions: advertising has already begin, and some pharmacies and clinics have their supplies now. But, because the effectiveness of vaccine can wane over time, CDC recommends against shot in August. Many pharmacies and clinics will start immunizations in early September. Generally, influenza viruses start circulating in mid - to late October but become more widespread later, in winter. It takes about two weeks after getting shot for antibodies which circulate in the blood and thwart infections to build up. Young, healthy people can begin getting their flu shots in September, and elderly people and other vulnerable populations can begin in October, said Dr. Steve Miller, chief clinical officer for insurer Cigna. Cdc has recommended that people get Flu Vaccine by the end of October, but note it is not too late to get one after that because shots can still be beneficial and vaccination should be offered throughout flu season. Even so, some experts say not to wait too long this year, not only because of COVID - 19, but also in case shortages develop because of overwhelming demand. Get a shot because it protects you from catching flu and spreading it to others, which may help lessen the burden on hospitals and medical staffs. And there is another message that may resonate in this strange time. It gives people the sense that there are some things you can control, said Eduardo Sanchez, chief medical officer for Prevention at American Heart Association. While flu shots wont prevent COVID - 19, he say, getting one could help your doctors differentiate between diseases if you develop any symptoms like fever, cough, sore throat they share.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Goal of the Flu Vaccine

To understand how Flu Vaccine works, you need to understand how your immune system works first. Your immune system fights disease by remembering every single disease youve ever seen in your life. Seriously. Every one of them. In response, your body makes antibodies that tell your white blood cells which infections need to be destroy. If it help, think of antibodies as blue ink that explodes if somebody tries to steal something; now we all know who the thief is. Your body can crank out antibodies at moments notice for any disease youve ever come into contact with; they tag offending bacteria or viruses and your white blood cells come in and the offender dies a horrible death. Vaccines work by training your body's immune system. There are two types of vaccines: inactivate, and live / attenuate. Inactivate vaccines are essentially protein coat of whatever youre trying to vaccinate against. Think of it as what a bacteria or virus is wearing. Live / attenuate vaccines are viruses or bacteria that have been weak. Vaccine isnt what the virus is wearing, it is just a really weak version of the virus itself.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Viral Mutations

Just as natural selection HAs shaped evolution of humans, plants, and all living things on the planet, natural selection shapes viruses, too. Though viruses are technically living - they need host organism in order to reproduce - they are subject to evolutionary pressures. The Human Immune System uses a number of tactics to fight pathogens. The Pathogen's job is to evade the Immune System, create more copies of itself, and spread to other hosts. Characteristics that help virus do its job tend to be kept from one generation to another. Characteristics that make it difficult for a virus to spread to another host tend to be lose. Take, for example, virus that has mutation that make it particularly deadly to its human host and kills host within a few hours of infection. A virus needs a new, healthy host for its descendents to survive. If it kills its host before the host infects others, that mutation will disappear. One way hosts protect themselves from virus is to develop antibodies to it. Antibodies lock onto the outer surface proteins of virus and prevent them from entering host cells. Virus that appear different from other viruses that have infected host HAs advantage: host HAs have no pre - existing immunity, in form of antibodies, to that virus. Many viral adaptations involve changes to the virus ' outer surface. Below we look at two special cases of viral evolution: How evolution occurs in Influenza viruses and in human immunodeficiency virus. Both of these viruses are RNA viruses, meaning that their genetic material is encoded in RNA, not DNA. Dna is a more stable molecule than RNA, and DNA viruses have proofreading check as part of their reproductive process. They manage to use host cell to verify Viral DNA replication. If a virus makes a mistake in copying DNA, host cell can often correct the mistake. Dna viruses, therefore, do not change, or mutate, much. Rna, however, is an unstable molecule, and RNA viruses do have build - in proofreading step in their replication. Mistakes in copying RNA happen frequently, and the host cell does not correct these mistakes. Rna virus mutations are frequent and can have important consequences for their hosts. Maurice Hilleman and his colleagues at WRAIR identified a new influenza virus, Type A2, Asian Influenza, that caused the pandemic. Hilleman noticed news reports of severe influenza in Hong Kong. The number of cases and their description led him to think that a new type of Influenza was emerging and that a pandemic was threaten. Hilleman and his team obtained a sample of virus from a US serviceman. They soon determined that most people lack antibody protection from the new Influenza virus. Only a few elderly people WHO had survived the Influenza pandemic of 1889 - 1890 show antibody response to new virus. Hilleman jump - started vaccine production by sending virus samples to manufacturers and urging them to develop vaccine within four months.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Predictions and Production

Sept. 2 2020 - Every year since 2010, CDC HAs urged almost all Americans over 6 months old to get flu shot. And every year we fall far short - just half of the US gets vaccinated during the 2018 - 19 season. One reason: Some people believe shots just work. Because flu viruses mutate constantly and vaccine wears off over time, you can get vaccinated once and expect to be covered for years, as you can with other diseases. Vaccines must be changed each year, in hopes of matching ever - mutating viruses. And thatas been challenge. On average, itas been 40% effective, meaning itas prevents illness 40% of the time. Since health officials started tracking it in 2003, effectiveness of HAs varied from year to year, ranging from a low of 10% in 2004 - 05 to a high of 60% in 2010 - 11. Hereas what makes it so difficult. Therea no single flu virus. It comes in several strains, two most common being and B. Strain, more dangerous of two, has two subtypes that spread regularly among humans: and. And B strain, which tends to cause milder illness, get classified into two lines. From there, each one branches out further as new mutations occur. Awhen we talk about building Influenza Vaccine, we are not just trying to make vaccine for one virus, like with measles, say Michael L. Jackson, PhD, principal investigator For United States Influenza Vaccine Effectiveness Network from Kaiser Permanente Washington Health Research Institute. We are trying to make Vaccine for four different viruses all at once. Vaccines For and B viruses were first given in the 1940s. In 1947, investigators realized that mutations in viruses had made Vaccine ineffective, setting in motion the annual system we have now. Five years after that, World Health Organization established the Global Influenza Surveillance and Response System, which monitors changes in predominant flu viruses circulating each year. Today, more than 100 countries gather information about Flu year - round. Who collates that information and spearheads effort to predict which flu viruses will dominate in the coming year. Each new vaccine includes one, one, and one or two B viruses. For the Northern Hemisphere, those predictions take place in February - thatas right, while the current flu season is still in full swing, scientists must determine what should be in vaccine for next season. Thatas because making vaccine takes time - drugmakers need at least 6 months to produce enough doses. Flu viruses mutate quickly, and sometimes by time vaccine is ready, circulating virus HAs change, says Jeffrey Shaman, PhD, professor at Columbia University Mailman School of Public Health. Who led the development of the schoolas Flu forecasting System. Aso what actually comes out in the vaccine is not quite what they intend, he say. Another problem: Since they work so far ahead, sometimes virus predictions simply miss the mark.


Currently Licensed Seasonal Influenza Vaccines

Currently, licensed influenza vaccines focus on production of antibodies against viral HA protein, which bind host receptors to mediate viral entry. Strain - specific antibodies produced against HA neutralize virus and prevent infection. Current seasonal vaccines require annual evaluation and reformulation to keep pace with antigenic drift of circulating strains. This process is completed twice a year, once each for the northern and southern hemispheres. Antigenic drift results from mutations that occur because error - prone viral RNA - dependent RNA polymerase lacks proofreading function, resulting in mutations in HA and other viral proteins. Additionally, HA is under positive selection for antigenic escape from neutralization by pre - existing antibodies. Selection of vaccine composition for upcoming seasons vaccine must take place 7 to 8 months in advance of flu season to accommodate steps of vaccine production. There are three classes of licensed seasonal vaccines, including inactivated, live attenuate, and recombinant HA vaccines. All three vaccines are multivalent, with components representing influenza and B viruses anticipated to circulate in the next influenza season. Inactivated influenza vaccine is a split virion or subunit vaccine that contains 15g of each purified HA protein administered intramuscularly, or 9g of each purified HA protein administered intradermally. There is also a higher dose of antigen available for the elderly population aged 65 years and older, in which 60 g of each HA is administered in order to increase immunogenicity of the vaccine. The Trivalent inactivate vaccine contains H1N1 and H3N2 subtypes of influenza along with the predicted dominant lineage of influenza B. The recently licensed Quadrivalent influenza vaccine includes two lineages of influenza B along with H1N1 and H3N2 subtypes of influenza. Iiv induces strain - specific serum IgG antibody response and is licensed for individuals aged 6 months and older. The second licensed vaccine product is live attenuated influenza vaccine. This vaccine also contains a mixture of the same four influenza strains as QIV, but is administered intranasally as spray. Laiv contains live viruses with temperature - sensitive and attenuating mutations. As result of these mutations, vaccine virus is restricted in replication at temperature of lower respiratory tract, but can replicate at the cooler temperature of the nasal cavity. Vaccination with LAIV results in production of strain - specific serum IgG as well as mucosal IgA and T Cell responses. Laiv is also effective against some antigenically drifted strains of influenza. Laiv is license for healthy individuals between the ages of 2 and 49 years and the CDC recommends that children between the ages of two and eight years receive LAIV over IIV if available. The third licensed product is FluBlok, which is a recommended HA vaccine with HA proteins that are expressed in insect cells by baculovirus vectors. Flublok is currently licensed for adults aged 18 to 49 years and can be used by individuals WHO are allergic to eggs.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Advances in Flu Vaccination

Research is ongoing to find Universal flu Vaccine that will be effective against all strains. This could eliminate the need to develop new Vaccine each year, or even allow people to get vaccinations less often than yearly. While exciting prospect, Science just isn't there yet. What Science has prove, however, is the effectiveness of flu vaccination. Despite the aforementioned shortcomings, getting a flu shot is still the most effective way to prevent infection. The traditional way vaccine is manufactured is by inoculating fertilized chicken eggs with chosen viral strains. After a few days, fluid from eggs is harvested and purified to make vaccine. Both inactivated Influenza Vaccine and live attenuate Influenza Vaccine are made in this way. However, some influenza viruses, such as H3N2 viruses, grow poorly in chicken eggs. The process was approved in 2012 to allow growing viruses on cell cultures. This results in an egg - free vaccine that is safer for people WHO are severely allergic to eggs. The recommended process was approved in 2013. As of the 2019 to 2020 flu season, only one Influenza Vaccine is produced this way in the US. These are considered two significant advances. There are also developments in making vaccines for special populations and circumstances. For those aged 65 and over, high - dose and adjuvant vaccines have been develop. As the immune system's response wanes with age, these vaccines are designed to produce stronger response. Researchers have also developed intradermal Vaccine that uses less antigen, therefore stretching vaccine supply when necessary. It is injected under the skin rather than into muscle.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

A complicated immune system history

What is at play seems to be a phenomenon known as original antigenic sin. Flu Vaccines are designed to get the immune system to produce antibodies that recognize specific strains of virus someone may encounter in give year. These antibodies target unique sites in virus, and latch onto them to disable it. Once the immune system already has HAs antibodies to target give site on virus, it preferentially reactivates the same immune cells next time it encounters virus. This is efficient for the immune system, but the problem is that viruses change ever so slightly from year to year. Site antibodies recognize could still be there, but it may no longer be crucial one to neutralize viruses Antibodies produced from our first encounters with flu, either from vaccines or infection, tend to take precedence over ones generated by later inoculations. So, even when vaccine is good match for give year, if someone has HAs history with flu, immune response to new vaccine could be less protective. This story may be complicated by an additional factor, which is that the vaccine could induce weak immune response in many who receive it. We see that both vaccinated and unvaccinated people were infected with similar Flu viruses and that vaccine did elicit strong immune response from most people. In our study, say Yonatan Grad, MD, PhD, assistant professor of immunology and Infectious Diseases at Harvard Chan School of Public Health and co - author of the study. But when Cobey, Grad and their colleagues analyzed blood samples from people who got vaccinated that year, they saw no differences in antibody responses to vaccine or circulating strains. It seems that their immune systems do bother to recognize differences from egg mutations because they already recognize so many other sites on vaccine strain. Imagine influenza viruses are like different makes and models of cars, say Grad. Ferrets, who have seen influenza before, learn to tell the difference between closely related strainslike tell difference between Honda Civic and Toyota Camry. But people could distinguish between them and instead just saw cars. That is not to say egg adaptations do always matter. In a separate study from 2017, Cobey and a team led by researchers from the University of Pennsylvania found that egg adaptations do cause mismatches in the most common vaccines given in 2016 - 17, another rough season dominated by H3N2. Egg adaptations may be a factor during this year's record - breaking Flu Season as well. H3n2 is again the predominant strain making people sick, and the most common vaccine is the same one from last year with its potentially problematic egg adaptations.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

New vaccine alternatives

Peter Palese, microbiologist at Icahn School of Medicine at Mount Sinai in New York City, believes that today's flu vaccines come in for too much criticism. They are fairly good vaccines but theyre not perfect, he say. The main problem, he add, is that they elicit focused immune response against moving target. Humans are affected by two main types of influenza. Influenza and B can both contribute to seasonal flu, but some Influenza subtypes preferentially infect animal hosts. Sometimes these subtypes abruptly acquire the ability to infect humans, leading to pandemics such as one in 2009. Each year, the seasonal flu vaccine is designed to cover two strains each of Influenza and B, based on the public - health communitys best informed guess about which strains will be dominant that year. Every Influenza virus is stud with hundreds of molecular structures formed by a multifunctional protein called haemagglutinin. Haemagglutinin helps viruses to bind and penetrate host cells. It comprises bulky head attached to virus by slender stalk. Most of immune response is targeted at the head because it is highly expose, but there is also evidence that the head contains features that preferentially elicit strong antibody response. There are structured loops, and antibodies easily recognize loops that stick out like that, explains James Crowe, director of Vanderbilt Vaccine Center in Nashville, Tennessee. Unfortunately, these immunodominant elements are also highly variable between strains. Influenza viruses are particularly diverse. They are classified by numbers based on subtype of haemagglutinin protein and second viral protein know as neuraminidase, with even greater strain variation observed among those subtypes. For example, 2009 pandemic arose from a new strain of H1N1 subtype. The extent of haemagglutinin variability means that poor strain selection can leave recipients largely unprotected and even a good vaccine offers limited protection against future strains. In two years, viruses can change again so we can get re - infect and get disease, say Palese. Further complicating the quest for Universal flu Vaccine is the fact that our immune system is strongly bias by its earliest encounters with Influenza through phenomenon called imprinting or, as it has been dub, original antigenic sin. This means that individuals have strong antibody response to viruses with molecular features shared by strain encounter during their first exposure, but they essentially start from scratch when exposed to distantly related strains for the first time. Its not that you cannot see second viruses it just like your baby and you seeing it for the first time, says Crowe. Imprinting is a double - edge sword because early exposure to the right strain could theoretically produce far - reaching and vigorous protection in response to vaccination. But if children's first influenza encounter is with relatively unusual or atypical strain, vaccination might prove less effective in terms of rousing broadly protective immunity.


What are cell-based flu vaccines?

Observational studies have shown greater protection against flu or flu - like illness among people who receive Flucelvax compared to those who receive standard - dose egg - base vaccines. The potential advantage of cell culture technology is that it might permit faster start - up of the vaccine manufacturing process in the event of a pandemic. Cells used to manufacture Flucelvax Quadrivalent are kept frozen and bank. Cell banking ensure adequate supply of cells is readily available for vaccine production. Growing flu viruses in cell culture for manufacture of Flucelvax Quadrivalent is not dependent on egg supply. Cell - base flu vaccines that are produced using CVVs have the potential to be more effective than traditional egg - base flu vaccines.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Sources

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

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