Influenza, sometimes called “flu”, is a contagious respiratory illness caused by the influenza virus. It is one of the most common diseases in the United States that can infect people at any age. Influenza can cause mild to moderate illness, but sometimes, it can also cause severe complications.
According to the World Health Organization (WHO), flu can cause about 650,000 deaths yearly. As of October 28, 2022, the Centers for Disease Control and Prevention (CDC) has reported more than 300 deaths related to influenza for this flu season in the United States, including one pediatric death. The CDC also records over 800,000 flu cases and nearly 7,000 hospitalizations.
As we enter this year’s flu season, proper education is very important to prevent and fight the flu. In this article, you’ll learn how dangerous the flu is, what are the signs and symptoms, when to see a doctor, what’s the difference between COVID-19 and influenza and how to identify each, what flu antiviral drugs are available, and everything about flu vaccines for this season of flu.
What’s In The Article?
What Are The Dangers of the Influenza Virus?
Who Are At A Higher Risk Of Getting Influenza?
What Are The Symptoms of Flu?
When To See a Doctor?
What’s The Difference Between Flu And COVID-19?
Can I have Flu And COVID-19 At The Same Time?
How to Diagnose Influenza?
What are Flu Antiviral Drugs?
Flu Antiviral Drugs For Pregnant People
Flu Antiviral Drugs For Children
Flu Antiviral Drug Side Effects
What Is A Flu Vaccine?
How do Flu Vaccines work?
What Are The Benefits Of A Flu Vaccine?
Who Should Get A Flu Vaccine?
What's The Best Time To Get A Flu Vaccine?
How Long Does Protection Last After Getting a Flu Vaccine?
Where Can I Get The Flu Vaccine?
Can You Take The Flu Vaccine And COVID Booster Vaccine Together?
Are Flu Vaccines Safe?
Vaccine Side Effects
Final Thoughts
What Are The Dangers of the Influenza Virus?
Influenza treatments are available. Most patients recover within a few days or weeks. However, it can also lead to serious complications for people at high risk, such as those 65 years and older, pregnant people, children below two years old, and people with severe or chronic medical conditions.
Flu complications may include the following:
Sinus and ear infection
Pneumonia
Organ failure
Myocarditis
Bronchitis
Encephalitis
According to the CDC, “flu virus infection of the respiratory tract can trigger an extreme inflammatory response in the body and can lead to sepsis.” Flu can also worsen the condition of people with chronic diseases such as asthma and heart disease.
Who Are At A Higher Risk Of Getting Influenza?
Everyone is prone to having an influenza virus. It easily goes away from people with a healthy body and strong immune system. However, some may develop serious complications.
Below is a list of some conditions that can make you more vulnerable to getting the influenza virus:
Pregnant women
Living in long-term care facilities
Children younger than two years old
Here are certain conditions that can increase your risk of developing flu complications:
Age (65 years and above for adults and below two years old for children)
Asthma and other chronic lung illnesses
Liver disease
Renal conditions
Metabolic disorders
Neurologic and neurodevelopment disorders
Blood disorders
Obesity
A weak immune system caused by medications or diseases
History of stroke
Long-term medications with drugs containing aspirin or salicylate (for people below 19 years of age)
What Are The Symptoms of Flu?
People who get the flu can experience the following symptoms:
Fever
Cough
Runny nose
Sore throat
Muscle aches
Fatigue
Headaches
While these are the common signs and symptoms, not everyone with flu will experience fever or chills. Some patients may also experience vomiting and diarrhea, but these are more common in children than adults.
When To See a Doctor?
In most cases, flu can be treated at home using antiviral medications without needing to visit a physician. However, you should seek medical care if you experience the following emergency signs of complications.
Emergency symptoms for adults:
Shortness of Breath
Chest pain
Recurring fever or cough
Persistent dizziness
Abdominal pain
Severe muscle pain
Seizures
Inability to urinate
Severe weakness
Worsening of existing chronic medical conditions
Emergency symptoms for children:
Difficulty breathing
Dehydration
Pale or bluish lips or skin
Chest pain
Severe muscle pain
Recurring fever or cough
Seizures
Fever above 104°F
Worsening of existing chronic medical conditions
What’s The Difference Between Flu And COVID-19?
Flu and COVID-19 are both contagious respiratory illnesses caused by different viruses. Influenza viruses cause flu, while COVID-19 is caused by a coronavirus called SARS-CoV-2.
Laboratory tests, such as PCR tests, are needed to differentiate these two infectious diseases since it can be difficult to determine flu from COVID-19, and both can have the same symptoms.
According to the CDC, here are some notable differences between flu and COVID-19 infection:
COVID-19 is more contagious than the flu.
COVID-19 can cause more severe conditions.
It can take longer for people with COVID-19 to show symptoms from the day of infection.
People with COVID-19 can spread the disease longer than those with the flu.
COVID-19 and flu infection can have similar symptoms, which include the following:
Fever or chills
Headache
Cough
Sore throat
Runny nose
Difficulty breathing
Fatigue
Muscle aches
Vomiting
Diarrhea
Change in the sense of taste or smell (more common with COVID-19)
While flu and COVID-19 can have no symptoms at all, flu symptoms typically show within one to four days after the infection, while COVID-19 symptoms usually appear within two to five days and last up to 14 days.
Both flu and COVID-19 can spread through close contact with an infected person. The virus can spread through small particles or droplets from an infected person who coughs, talks, or sneezes.
The virus can enter your body through your nose, mouth, or eyes. While breathing in the virus is the major transmission means, you can also get it through skin-to-skin contact or touching an object with a virus.
COVID-19 virus can spread more quickly than the flu virus, thus, considering it more contagious, according to the CDC. It can be transmitted before an infected individual shows symptoms. However, asymptomatic people who don’t show symptoms can also pass the virus. Therefore, practicing healthcare protocols is crucial to avoid getting infected by asymptomatic infections.
People infected with the COVID-19 virus are said to have more serious illnesses. High-risk people, such as those with existing medical conditions, older adults, and pregnant women, are more vulnerable to severe complications caused by flu and COVID-19. However, the CDC stated that hospitalization and death are still possible for healthy people with COVID-19.
COVID-19 and flu can have similar complications, such as multiple-organ failure, sepsis, and pneumonia. Complications like blood clots and multisystem inflammatory syndrome can also occur in COVID-19 patients.
The CDC also stated, "Secondary bacterial infections are more common with influenza than with COVID-19.” Patients with COVID-19 infections can have post-COVID conditions that can last for several weeks or months.
The FDA-approved anti-viral flu treatment drugs are not authorized for COVID-19. Flu vaccines don’t provide protection against COVID-19. Likewise, COVID-19 vaccines cannot be used against the flu virus.
Can I have Flu And COVID-19 At The Same Time?
While it’s a rare condition, according to the CDC, you can have COVID-19 and flu simultaneously. Testing should be conducted to confirm a coinfection. Severe illnesses can also occur in people with this coinfection than those with either COVID-19 or influenza. Experts are still conducting studies to understand this coinfection further.
How to Diagnose Influenza?
You might have influenza if you experience flu symptoms like cough, fever, body pain, and headache. However, Lab tests are needed to differentiate flu from other respiratory illnesses. Lab tests can help you get proper treatment and decrease the risk of complications.
Rapid influenza diagnostic tests (RIDTs) can detect the flu virus antigen in your respiratory specimens. However, According to the CDC, it may not be as effective as other lab tests for the flu. This test can deliver results after 10 to 15 minutes.
Rapid molecular assays are molecular influenza diagnostic test that is said to be more accurate than RIDTs and can provide results after 15 to 20 minutes. This diagnostic test can detect the virus RNA in your respiratory specimens.
Other lab tests for detecting flu are reverse transcription polymerase chain reaction (RT-PCR), immunofluorescence assay (IFA), and viral culture. These swab tests can produce results after several hours and are more accurate than RIDTs and rapid molecular assays.
What are Flu Antiviral Drugs?
Flu antiviral drugs are medications used for influenza treatment, such as pills, IV solution, liquid medicine, or an inhaled powder. These antiviral drugs require a prescription from a healthcare provider.
Flu antiviral drugs should be given within two days after the flu starts. It can help to reduce flu symptoms and prevent further complications. Early treatment can also help immunocompromised individuals and others susceptible to severe illness to lessen the risk of hospitalization and death.
Oseltamivir phosphate, baloxavir marboxil, zanamivir, and peramivir are the four FDA-approved flu medications that CDC recommends. Zanamivir is an inhaled powder medication for flu treatment, but people with breathing problems cannot use it.
Peramivir is an intravenous solution that healthcare providers can administer to patients six months and older. Oseltamivir phosphate can be given as a pill or liquid solution for people 14 days and older. Baloxavir is given in single doses. Oseltamivir and zanamivir should be administered twice daily for five days.
The CDC doesn’t recommend Baloxavir for people with progressive disease and hospitalized patients.
Flu Antiviral Drugs For Pregnant People
Studies and research show that oseltamivir is safe and effective to use by pregnant people to treat influenza. Baloxavir is not recommended for pregnant or lactating women.
Flu Antiviral Drugs For Children
Oseltamivir can be given to children as an oral medicine for flu treatment. The CDC recommends using this drug for children from birth. Children seven years and above can also use Zanamivir, except those with underlying respiratory illness.
Children six months and older can also use peramivir to treat the flu, while those 12 years and older can use Baloxavir. It is also recommended for children below 12 to five without any underlying respiratory illness.
Flu Antiviral Drug Side Effects
Like any other antiviral drug, flu antiviral drugs can have different side effects. These can vary for each medication.
Oseltamivir's side effects may include the following:
Respiratory problems
Vomiting
Nausea
Bloating
Diarrhea
Dizziness
Headache
Possible side effects of baloxavir marboxil may include the following:
Cough
Sore throat
Runny nose
Difficulty breathing
Fever
Headache
Muscle pain
Weakness
Zanamivir can have the following side effects:
Headache
Dizziness
Diarrhea
Nausea
Vomiting
Nasal irritation
Peramivir can also have the following side effects:
Diarrhea
Constipation
High blood pressure
Insomnia
What Is A Flu Vaccine?
Flu vaccines, also called flu shots, are vaccines that protect against the infection of the influenza virus. These vaccines are available as injectables (flu shots) or nasal sprays.
Flu vaccines are proven effective in protecting against the four types of influenza virus: two influenza A viruses and two influenza B viruses.
The US Food and Drug Administration (FDA) has approved three production technologies for flu vaccine development. These are egg-based, cell-based, and recombinant flu vaccines.
The egg-based method uses candidate vaccine viruses (CVVs) to grow and replicate in fertilized hen’s eggs. The fluid which contains the virus is collected to purify the virus antigen. It is the most common production method for manufacturing flu vaccines.
Another process approved by the FDA is called cell-based production. While the egg-based method allows the virus to replicate in eggs, this method uses cell-grown CVVs in developing vaccines. CVVs are collected and then injected into cultured mammalian cells to enable them to reproduce.
Recombinant technology is another vaccine production method that doesn’t use CVVs and chicken eggs for vaccine development. A certain gene, which is used to make a surface protein found in flu viruses called hemagglutinin (HA), will be combined with a virus called “baculovirus” that grows in insects. This process will create recombinant baculovirus that will be injected into host cells to reproduce. Then, the HA will be isolated from the host cells and purified. HA is an antigen that helps our immune system to develop a strong defense called antibodies against the virus.
CDC recommends that people six months and older get a flu shot yearly. Here are the different types of flu vaccines available for different age groups of people according to the CDC:
Egg-Based Standard-Dose Quadrivalent Influenza Vaccines
. These are standard-dose flu vaccines developed using a virus from eggs and have been approved to administer to people as young as six months old.
Flucelvax Quadrivalent Vaccines
. These cell-based vaccines are developed using a virus from cultured cells of mammals. People six months older are eligible to get these vaccines. According to the CDC, this vaccine is potentially more effective than egg-based flu vaccines.
. Flublok Quadrivalent vaccines are produced using recombinant technology. It contains antigens that help the immune system build antibodies against the flu virus. These vaccines can be given to people 18 years of age and above.
Egg-Based Fluzone High-Dose Quadrivalent Vaccines
. Fluzone high-dose vaccines contain four times the amount of antigen compared to other standard flu vaccines. This high antigen dose gives people 65 years and older stronger protection against the flu.
. Fluad Quadrivalent is an egg-based standard-dose vaccine developed using adjuvant MF59 for a better immune defense against flu viruses. This vaccine is approved only for people 65 years of age and older.
. FluMist Quadrivalent vaccines are egg-based nasal spray flu vaccines, also known as live attenuated influenza vaccines (LAIV), developed using live attenuated flu viruses. These vaccines are proven effective in protecting against influenza A H1N1, influenza A H3N2, and two influenza B viruses.
How do Flu Vaccines work?
Vaccines contain inactivated or weakened viruses that can help the human body recognize an antigen of the virus. These viruses cannot infect your body. Instead, they enable the immune system to develop antibodies that will give protection against viruses.
What Are The Benefits Of A Flu Vaccine?
Influenza is a contagious disease that can infect anyone and cause severe conditions in high-risk people. Getting a flu vaccine effectively prevents this illness and reduces your risk of complications.
Although it’s still possible to be infected with the flu virus even if you’re vaccinated, flu vaccines can make your symptoms milder and reduce the risk of hospitalization and death. You will likely recover sooner than those who are not vaccinated. It can also help lessen the cost of consultation and additional medications.
Flu vaccines can also protect people at a higher risk of getting a serious illness from the virus, such as those with chronic health conditions, adults, and children.
Flu vaccines are also proven to be effective in preventing the worsening of chronic diseases. A study shows that flu vaccines are associated with lower cardiovascular events rates and reduce hospitalization cases for people with diabetes and lung disease.
Pregnant women vaccinated with flu vaccines are less likely to have acute respiratory infections related to flu viruses. CDC also stated that this vaccine protects the baby for several months after being born when the vaccine is given during pregnancy.
Getting the flu vaccine not only protects you from the virus but also enables you to protect other people around you who are more susceptible to the disease, like infants, children, and people with chronic medical conditions.
Who Should Get A Flu Vaccine?
The CDC recommends people six months and older get a flu vaccine. People who are at higher risk of flu complications should also be vaccinated. However, there are some exceptions to flu vaccines. It should also be administered according to age, current health status, medical history, and hypersensitivity reactions to vaccine components.
Pregnant women and those with medical conditions and egg allergies can still get a flu shot. However, it is recommended that you talk to your healthcare provider first if you have an allergic reaction to eggs and any vaccine component or if you have a history of Guillain-Barré Syndrome (GBS).
People two to 49 years of age are approved to get nasal spray vaccines. Children below two years and 50-year-old adults shouldn’t get these vaccines. Pregnant individuals, immunocompromised people, and those with severe allergies to any components of flu vaccine are also not eligible to get the nasal spray vaccine.
People two to 17 years old taking medications with aspirin or salicylate shouldn’t also get a nasal spray vaccine. Those with cerebrospinal fluid (CSF) leaks or cochlear implants can also not take these vaccines.
People with chronic medical conditions that can put them at a higher risk of getting severe flu complications, asthma, or recently taking influenza antiviral drugs should talk to a healthcare provider before getting the nasal spray flu vaccine.
People with moderate to severe illnesses usually are not allowed to be vaccinated until they recover.
What's The Best Time To Get A Flu Vaccine?
According to the CDC, most people should get the flu vaccines in September and October. However, vaccination after October would still be effective against the influenza virus. Generally, the best time to be vaccinated is before the start of flu season. The flu season in the US typically occurs from October to May, during fall and spring.
Since the vaccine’s efficacy decreases, it is not recommended, especially for adults and pregnant women, to get vaccinated earlier in July or August. However, they can be considered for vaccination during these months if they are in their third trimester of pregnancy to help protect the baby after birth for a few months.
Some children, such as those six months to eight years old, are recommended to get vaccinated once vaccines are available since they need two doses, and the second dose is administered four weeks after the first dose. However, those who only need one dose can be vaccinated in July or August.
How Long Does Protection Last After Getting A Flu Vaccine?
As your body’s immunity against the influenza virus decreases from the time you receive vaccination, the CDC recommends annual vaccination for people six months and older.
Experts are also conducting research and studies each year to identify the flu vaccine’s efficacy since flu viruses are constantly changing. It means that this season’s flu vaccine can only protect you for this period and may not be effective for the next year’s flu season.
Where Can You Get The Flu Vaccine?
Flu vaccines are widely available in many clinic sites where you can schedule an appointment for your vaccination. Some businesses also provide free on-site flu vaccinations for their employees.
Can You Take The Flu Vaccine And COVID Vaccine Together?
You can take the flu and COVID vaccines together if you are scheduled for both. It is called “coadministration,” a medical term that refers to getting two vaccines together in one visit.
Experts recommend the coadministration of vaccines because of the following reasons:
It ensures that you get all the vaccines you need without missing opportunities
It helps simplify the immunization schedule
It helps reduce the risk of needle sticks
It helps lessen the pain of injection and anxiety in children
It is more convenient to some people than having separate visits for vaccination
One study shows that adverse reactions, such as headache and muscle aches, more likely occurred in people who got these vaccines together than in those who only got COVID-19 booster shots. However, these adverse reactions don’t last long, and the CDC stated that clinical trials have proven that these vaccines are safe to administer together.
Can You Get Flu Virus Infection From Flu Vaccines?
You cannot get influenza from the flu vaccine since it contains no infectious virus. Flu vaccines contain either an inactivated virus or a live attenuated virus. An inactivated virus is a killed pathogen that cannot replicate in the human body, while a live attenuated virus is a weakened virus that is no longer infectious.
Are Flu Vaccines Safe?
Yes, flu vaccines are safe. Experts have been conducting research and studies to ensure the safety of the flu vaccine. It is safe to administer to pregnant women, adults, and children with certain considerations. For over 50 years, its safety and efficacy have been proven by many people in the United States.
Vaccine Side Effects
While proven safe and effective, flu vaccines can have side effects, too, just like any other medication. These side effects are usually mild and will go away within a few days.
Common side effects of flu shots can include the following:
Redness and swelling in the injection site
Headache
Body pain
Fatigue
Fever
Nausea
Fainting
Common side effects of nasal spray vaccines in adults can include the following:
Cough
Runny nose
Headache
Sore throat
Common side effects of nasal spray vaccines in adults can include the following:
Low-grade fever
Vomiting
Runny nose
Wheezing
Headache
Body pain
You should also monitor for any severe allergic reactions after vaccination which can include the following signs and symptoms:
Weakness
Dizziness
Difficulty breathing
A fast heartbeat
Hoarseness
Swelling around the eyes or lips
Hives
Paleness
Seek medical help if you experience these symptoms of severe allergic reaction. These can occur within a few moments after your vaccination.
Final Thoughts
Influenza is a common illness in adults and children. Proper treatment should be administered to prevent risks and complications. Healthcare workers are in a crucial position in combatting influenza, and they should be knowledgeable and always updated about the flu season.
AchieveCE is an accredited course provider that offers a flu shot webcast. This webcast is designed for pharmacists to help them understand flu season's impact on their scope of practice.
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