How Flu Vaccine Virus Strains Are Selected
Every year, in late February or early March, before that years flu season ends, the FDA, the World Health Organization , the CDC, and other public health experts collaborate on collecting and reviewing data from around the world to identify the flu viruses likely to cause the most illnesses during the next flu season.
Following that process, the FDA convenes its vaccines advisory committee, consisting of outside experts, to discuss the WHO recommendations and to consider which flu viruses are expected to circulate in the U.S. The committee also reviews data about which flu viruses have caused illnesses in the past year, how the viruses are changing, and disease trends for the U.S. The FDA takes that information into account before it selects the virus strains for FDA-licensed manufacturers to include in their vaccines for use in the U.S.
The closer the match between the virus strains chosen for the vaccine and the circulating strains causing disease during flu season, the better the protection that the flu vaccine provides. Although the vaccine and viruses may not be an exact match in some years, that does not mean the vaccine is not benefiting people. Available data show that the vaccine can reduce the severity of illness in people who get vaccinated but still get sick.
How The Flu Vaccine Works
Development of the seasonal flu vaccine actually begins many months ahead of flu season. The viruses used in the vaccine are based on extensive research and surveillance into which strains will be most common during the upcoming season.
Seasonal flu vaccines protect against two types of influenza viruses: influenza A and influenza B. They can also be either trivalent or quadrivalent.
The trivalent vaccine protects against three flu viruses: two influenza A viruses and an influenza B virus.
The quadrivalent vaccine protects against the same three viruses as the trivalent vaccine, but it also includes an additional influenza B virus.
What This Means For Your Annual Flu Shot
Considering all the influenza viruss tricks for infecting humans, its remarkable weve created a vaccine that works at all. And in fact, the vaccine prevents thousands of deaths every year. Most years, the vaccine cuts your chance of catching the flu in half, but its hard to get much better odds than that from it.
Our vaccine process is sort of always one step behind because of this long production process and trying to update the vaccine to whats circulating, Dr. Hensley said. The World Health Organization meets twice a year, once for the Southern Hemisphere and once for the Northern Hemisphere, to examine global flu surveillance and recommend the flu strains they expect will cause the most illness.
This puts a huge burden on manufacturers, Dr. Karron said. In the Northern Hemisphere, they learn the W.H.O. recommendations in February and have only about six months to make vaccines. They sell it very cheaply, Dr. Karron said, about $10 to 20 a dose, and have to throw away anything unsold at the end of the season. The flu vaccine is not a blockbuster moneymaker, she said.
Understanding the flu viruss trickery explains some of the vaccines quirks. Why do some vaccine strains partly protect against nonvaccine strains? The HA and NA may look similar enough to the vaccine strain that antibodies attack it anyway.
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The Flu Vaccine Is Safe
To ensure that the flu vaccine is safe, effective, and of high quality, the FDA prepares and provides reagents to manufacturers that they need to make their vaccine and to verify its identity and potency. The FDA also inspects manufacturing facilities regularly and evaluates each manufacturers vaccine annually before it can be approved.
The FDAs oversight doesnt end there. After manufacturers have distributed their vaccines for use by the public, the FDA and CDC work together to routinely evaluate reports of adverse events following vaccination submitted by vaccine manufacturers, health care providers and vaccine recipients to the Vaccine Adverse Event Reporting System .
Additional efforts are in place to monitor vaccine safety. The FDA partners with private organizations that collect health care data and other federal agencies to further evaluate the safety and effectiveness of the influenza vaccines and other vaccines that the FDA has approved or authorized for emergency use.
The Biologics Effectiveness and Safety Initiative is one of the programs the FDA utilizes to assess vaccine safety and effectiveness in real-world conditions, reflecting patient care and the real-world use of the influenza vaccine and other vaccines in the U.S. In addition, the CDC maintains the Vaccine Safety Datalink program, which evaluates the vaccines safety similar to the BEST Initiative. VSD receives its data from nine integrated health care organizations in the U.S.
You Have An Unrelated Case Of The Flu
The vaccine can take up to two weeks to become effective after you receive it. If you come down with the flu in that period, it’s likely that you were already exposed to the virus before receiving your shot. You didn’t get the flu from the shot.
As well, the strains of flu included in the flu shot vary from year to year. Unfortunately, it is particularly prone to change, with new strains appearing often. Scientists work to target the strains that will be the most prevalent that season so that the vaccination can be tailored accordingly. Despite their best efforts, they may sometimes get it wrong.
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Will Side Effects Be Worse If You Get Both Vaccines At The Same Time
As flu season approaches, many people are thinking about vaccine timing. Theyre wondering if they should get their flu shot first and then get a COVID booster, or if they should get a COVID booster first and then get a flu shot.
They should actually do both, says Dr. Jonathan H. Watanabe, PharmD, PhD, associate dean of assessment and quality and professor of clinical pharmacy at the University of California, Irvine. Theres not any contraindication, at least from the CDC, about whether they could take both, and thats probably what I would recommend. From reviewing prior studies of non-COVID vaccines, we can say that likelihood of having a side effect is generally the same when vaccines are given at the same time as when they are injected on separate visits.
In fact, you could even get them at the same time, if theyre offered at the same place. Its hard to know if youll feel lousy afterwardas many people did after their first COVID vaccine doses.But if thats your concern, you could space them out a little.
Its more personal preference, says Dr. Watanabe, who also serves as an appointed member of the National Academies of Sciences, Engineering, and Medicine Forum on Drug Discovery, Development, and Translation. Its not CDC guidance.
But it is safe, says Dr. Smith.And for convenience, that might be the strategy, to go ahead and get them together on your visits, he says.
When Should I Get Vaccinated
You should get a flu vaccine before flu viruses begin spreading in your community since it takes about two weeks after vaccination for antibodies to develop in the body and provide protection against flu. Make plans to get vaccinated early in the fall, before flu season begins. CDC recommends that people get a flu vaccine by the end of October. However, getting vaccinated early is likely to be associated with reduced protection against flu infection later in the flu season, particularly among older adults. Vaccination should continue to be offered throughout the flu season, even into January or later. Children who need two doses of vaccine to be protected should start the vaccination process sooner of vaccine to be protected should start the vaccination process sooner because the two doses must be given at least four weeks apart.
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Flu Vaccine Side Effects
Flu vaccines are very safe. All adult flu vaccines are given by injection into the muscle of the upper arm.
Most side effects are mild and only last for a day or so, such as:
- slightly raised temperature
- muscle aches
- sore arm where the needle went in this is more likely to happen with the vaccine for people aged 65 and over
Try these tips to help reduce the discomfort:
- continue to move your arm regularly
- take a painkiller, such as paracetamol or ibuprofen some people, including those who are pregnant, should not take ibuprofen unless a doctor recommends it
Why Do I Need A Flu Vaccine Every Year
A flu vaccine is needed every season for two reasons. First, a persons immune protection from vaccination declines over time, so an annual vaccine is needed for optimal protection. Second, because flu viruses are constantly changing, flu vaccines may be updated from one season to the next to protect against the viruses that research suggests may be most common during the upcoming flu season. For the best protection, everyone 6 months and older should get vaccinated annually.
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So Who Should Get A Flu Shot And When
The flu vaccine offers the highest level of protection in the first three to four months months after vaccination. The season generally peaks between June and September although this year we have seen a much earlier than usual start to the flu season. Its unclear whether this early start will mean a longer flu season or an early finish. So its not too late to get vaccinated.
Flu vaccines are recommended for everyone aged six months and over, but are particularly important for people who are more at risk of complications from influenza, including:
- Aboriginal and Torres Strait Islander people aged six months and over
- children aged six months to five years
- pregnant women
- people aged 65 years or over
- people aged six months or over who have medical conditions that mean they have a higher risk of getting serious disease.
Should I Get The Flu Vaccine If I’m Pregnant Or Breastfeeding
Years of studies and observation show that you can safely get a flu shot at any time, during any trimester, while you are pregnant or breastfeeding. Babies cannot get the vaccine until six months old. Because antibodies from the vaccine pass onto a fetus in the womb and through breast milk, you protect your baby even more by getting vaccinated.
Pregnant people should not get the nasal spray form of the flu vaccine. Those with a life-threatening egg allergy should not get the flu vaccine, whether pregnant or not.
SourcesFlu & Pregnancy- CDC
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Why Do I Get Sick After Getting A Flu Shot
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- Soreness, redness, and/or swelling from the shot.
- Muscle aches.
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Yes You Can Get These Shots At The Same Time
When the COVID-19 vaccines were first released, the timing was a concern. Experts recommended not getting vaccinated for anything else for a certain amount of time before or after getting vaccinated for COVID.
But you no longer need to figure out how to space out getting a seasonal flu shot and a COVID shot, regardless of which dose of the COVID series youre getting.
It used to be the case that we would advise people to separate the COVID shot for two weeks before or after any other vaccine, saysDr. Darvin Scott Smith, MD, chief of infectious disease and geographic medicine for Kaiser Permanente in Redwood City, in California. Thats no longer the directive.
Over time, as millions of people received doses, experts gained more knowledge about the COVID-19 vaccine. They were able to look at whether the timing of vaccine administration was an issue, explains David Souleles, MPH,director of the COVID-19 Response Team at the University of California, Irvine.
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There are no timing concerns now, he says.
Flu season typically starts in the fall, with cases of flu beginning to ramp up in October. Peak flu season usually occurs between , although flu activity can last through May, according to the Centers for Disease Control and Prevention .
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What This Means For You
As flu season approaches, the CDC is advising people to get their flu shot by the end of October. If you have not yet received all your initial COVID vaccine dose or doses, or if you are eligible for a booster dose, its safe to get both vaccines on the same day.
The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.
Why Should People Get Vaccinated Against Flu
Influenza is a potentially serious disease that can lead to hospitalization and sometimes even death. Every flu season is different, and flu can affect people differently, but millions of people get flu every year, hundreds of thousands of people are hospitalized and thousands to tens of thousands of people die from flu-related causes every year. Flu can mean a few days of feeling bad and missing work or it can result in more serious illness. Complications of flu can include bacterial pneumonia, ear infections, sinus infections and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes. An annual seasonal flu vaccine is the best way to help protect against flu. Vaccination has been shown to have many benefits including reducing the risk of flu illnesses, hospitalizations and even the risk of flu-related death in children. While some people who get a flu vaccine may still get sick, flu vaccination has been shown in several studies to reduce severity of illness.
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What Kinds Of Flu Vaccines Are Available
CDC recommends use of any licensed, age-appropriate influenza vaccine during the 2021-2022 influenza season. Available influenza vaccines include quadrivalent inactivated influenza vaccine , recombinant influenza vaccine , or live attenuated influenza vaccine . No preference is expressed for any influenza vaccine over another.
Quadrivalent flu vaccines include:
Are any of the available flu vaccines recommended over others?
Yes, for some people. For the 2022-2023 flu season, there are three flu vaccines that are preferentially recommended for people 65 years and older. These are Fluzone High-DoseQuadrivalent vaccine, Flublok Quadrivalent recombinantflu vaccine or Fluad Quadrivalent adjuvanted flu vaccine. On June 22, 2022, CDCs Advisory Committee on Immunization Practices voted unanimously to preferentially recommend these vaccines overstandard-dose unadjuvanted flu vaccines. This recommendation was based on a review of available studies which suggests that, in this age group, these vaccines are potentially more effective than standard dose unadjuvanted flu vaccines. There is no preferential recommendation for people younger than 65 years.
What if a preferentially recommended flu vaccine is not available?
If one of the three preferentially recommended flu vaccines for people 65 and older is not available at the time of administration, people in this age group should get an age-appropriate standard-dose flu vaccine instead.
Who Should Vaccinate?
Too Late For The Flu Vaccine
Flu viruses usually cause the most illness during the colder months of the year. In the United States, flu season is from October to May. Most cases happen from late December to early March.
It’s best to get the flu vaccine early in flu season, ideally by the end of October. That way, the body has time to make antibodies that protect it from the flu.
What if you aren’t vaccinated by then? Getting the vaccine later is better than not getting it at all. It’s still flu season well into spring. Even then it’s not too late for you and your family to get the flu vaccine. Many health care providers give flu vaccines through May if the flu virus is still circulating.
Getting a missed flu vaccine late in the season is especially important for people who travel. That’s because the flu can be active around the globe from April to September.
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Safety And Side Effects
The inactivated flu vaccine does not contain the live virus and cannot cause flu. Flu vaccines have a very good safety record. The most commonly reported side effects of flu vaccines are:
- pain, swelling, bruising, hardness or redness at the injection site
- slightly raised temperature
- feeling generally unwell
A higher rate of these common side effects has been reported with Fluad, an adjuvanted trivalent vaccine which was recommended for people aged 65 and over in previous years. This year, a quadrivalent inactivated influenza vaccine which also uses an adjuvant is being offered to people aged over 65. Side effects usually last 1-3 days.
There are several different makes of flu vaccine available each year. For more information on side effects, ask for the Patient Information Leaflet for the vaccine you are offered. Additional information about vaccine side effects, anaphylaxis and adverse reactions can be found here.
Why The Cdc Updated Its Guidance
When the COVID-19 vaccines first came out, the U.S. Centers for Disease Control and Prevention recommended not getting other vaccines for 14 days before and after each COVID-19 dose.
The agency changed its guidance in May after data showed that the COVID-19 vaccine was safe and that other vaccines would not interfere with the immune response, experts say.
“That was because we wanted to really assess the side effects of the COVID vaccine as we rolled it out. We didn’t want to get that confused by giving other vaccines at the same time, says William Schaffner, M.D., a professor of infectious diseases at Vanderbilt Medical Center in Nashville, Tennessee.
Now, the CDC says COVID-19 vaccines and other vaccines can be administered without regard to timing. This includes simultaneous administration of COVID-19 vaccine and other vaccines on the same day, as well as coadministration within 14 days.
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