Influenza, or flu, is a highly contagious respiratory infection that affects the throat, nose, and lungs. Many medicinal options are available to help prevent and treat the symptoms of flu.

There are 4 types of seasonal influenza viruses, with influenza A and influenza B being the most common cause of seasonal epidemics in the United States, as well as globally, almost every winter season.

These viral infections can spread through tiny droplets that form when people talk, cough, or sneeze.

According to the World Health Organization (WHO), influenza causes 3–5 million cases of severe disease along with 250,000–500,000 deaths every year globally. However, many options are available to prevent acquiring the flu virus and to reduce severity of symptoms.

In this article, we will discuss the available treatment options for influenza.

A collage of medicines and a person blowing their nose.Share on Pinterest
Design by MNT; Photography by simonkr/Getty Images & FG Trade/Getty Images

Influenza vaccines, often known as flu shots, help to protect against infection by influenza viruses. There are many available flu vaccines. People must consult with doctors to know which vaccine is most suitable for them.

According to the Centers for Disease Control and Prevention (CDC), all people who are 6 months of age and older should get a flu vaccine every year to prevent flu along with its serious complications. The different flu vaccines that are available include:

Unadjuvanted quadrivalent influenza shot

Experts manufacture this vaccine using viruses from eggs. As the name suggests, this vaccine can protect against 4 different flu viruses, including two influenza A viruses and two influenza B viruses.

Examples include Afluria Quadrivalent, Fluarix Quadrivalent, FluLaval Quadrivalent, and Fluzone Quadrivalent.

Quadrivalent cell-based influenza shot

Instead of using eggs, this vaccine uses viruses from cell cultures. This vaccine has approval for people 6 months and older. An example of this vaccine is Flucelvax Quadrivalent.

Recombinant quadrivalent influenza shot

Another egg-free option, this vaccine has approval for people over 18 and uses a recombinant approach. This means it uses a specific part of the flu virus, such as the antigen, to generate an immune response. An example of this vaccine is Flublok Quadrivalent.

Adjuvanted quadrivalent influenza shot

An adjuvant refers to an ingredient in some vaccines that can help create a stronger immune response. This vaccine includes MF59, an oil-in-water emulsion that helps to reduce the amount of virus necessary for producing a vaccine.

Fluad Quadrivalent has approval for people 65 years of age and older and is an example of this type of vaccine.

High-dose quadrivalent influenza shot

This type of vaccine contains 4 times the antigen compared with a standard dose. This vaccine has approval only for people aged 65 years and older.

The higher dose of antigen in the vaccine intends to give older adults a better immune response, and, therefore, better protection against flu. The brand name of this vaccine is Fluzone High-Dose Quadrivalent.

Live attenuated quadrivalent influenza shot

Some people may refer to this type as a nasal spray vaccine. Rather than an injection, a person receives this vaccine through their nose. It uses a live attenuated, or weakened, version of the flu virus.

This vaccine has approval for healthy nonpregnant people aged 2–49 years old. The brand name for this vaccine is FluMist Quadrivalent.

Jet injector quadrivalent influenza shot

Instead of a needle, this type of vaccine uses a high-pressure, narrow stream of fluid to penetrate the skin. Evidence suggests that the jet injector method provides a similar level of protection to traditional flu shots. The brand name of this vaccine is AFLURIA Quadrivalent.

Although these vaccines are effective in protecting against influenza, they can cause side effects such as swelling or redness in the region of the shot, muscle ache, fever, and headache. Live flu vaccines may also cause a runny nose and wheezing.

As with any medicine, there is a remote chance of a life threatening allergic reaction to these vaccines.

Flu antiviral drugs describe prescription medicines that target flu viruses. They are available in different forms, such as pills, liquid, powders, or an intravenous solution.

These drugs typically work best when a person starts them within 2 days of becoming sick with flu symptoms. They can help to lessen flu symptoms and speed up recovery time. Antiviral drugs that are useful in the treatment of influenza include:

Oseltamivir phosphate (Tamiflu)

Oseltamivir is a neuraminidase inhibitor that is effective against both influenza A and B viruses. It blocks the viral neuraminidase enzyme, which is essential for influenza reproduction. It is available in oral forms such as capsules or powder suspensions.

Side effects may include nausea, vomiting, diarrhea, and abdominal cramps.

Zanamivir (Relenza)

Zanamivir is another type of neuraminidase inhibitor. It is available as an inhalation powder, which a person breathes in using a special inhaler that comes with the drug. Side effects can include bronchospasm, dizziness, and sinusitis.

Peramivir (Rapivab)

Peramivir is also a neuraminidase inhibitor. This drug is available as a colorless liquid solution inside vials. A person receives it intravenously, typically through a vein in the arm over a period of time. Side effects may include diarrhea, skin reactions, and neuropsychiatric events.

Baloxavir marboxil (Xofluza)

Unlike the other flu antivirals, baloxavir marboxil is a cap-dependent endonuclease inhibitor. This means it stops the virus from multiplying in the body by interfering with viral RNA transcription. This is the process viruses use to multiply and blocking this process stops viral replication.

It is available in oral forms such as capsules or powder suspensions. Side effects can include bronchitis, diarrhea, nausea, and headache.

Analgesics, also known as pain relievers, can help to lessen pain and fever symptoms that result from influenza. Common examples of over-the-counter nonopioid analgesics include acetaminophen, also known as paracetamol, and nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin.

Among them, acetaminophen is one of the most commonly available pain-relieving and fever-reducing medications available. The dose that doctors recommend for an adult usually ranges from 650–1000 milligrams (mg) every 4–6 hours, with a maximum dose of 4 grams per day.

The dosage that doctors recommend for NSAIDs will depend on the specific drug, and the product label should provide guidelines and instructions.

Nonopioid pain relievers are relatively safe for use in both adults and children when a person takes them correctly. Possible side effects can include nausea, constipation, and hypersensitivity reactions. Because excessive quantities of these drugs can be harmful, it is advisable for people to stick to recommended dosages.

Additionally, if taking other products to relieve flu symptoms, a person should check ingredients to ensure they ingest a safe amount. For example, other flu products may contain Tylenol or NSAIDs, which is why it is important for people to check all the products they take to stay within the maximum daily dose that doctors recommend.

Antitussives, which some people may refer to as cough suppressants, are compounds that can help reduce coughs. Coughing is a common symptom of the flu, which can irritate the throat and disrupt sleep.

Dextromethorphan is a common ingredient in many antitussive products. While researchers are still unsure exactly how it works, it may prevent coughs by suppressing the cough receptors of the central nervous system.

The dosage will vary depending on the formulation of the product. For example, for a liquid solution, adults and children aged over 12 can take a 10 milliliter (ml) dose every 6–8 hours and should not exceed 4 doses in a 24-hour period.

The most common side effects from antitussives may include nausea, gastrointestinal discomfort, drowsiness, and dizziness.

Expectorants help clear mucus from the airways, which can relieve congestion. Guaifenesin is a common ingredient in many expectorants.

It is usually available as a solution, and the recommended dosage for adults and children aged over 12 is 10–20 ml every 4 hours, and not to exceed six doses in a 24-hour period. Side effects can include irritation of the digestive tract, nausea, and vomiting.

Decongestants are compounds that can help provide relief from a blocked or stuffy nose. They are available in many formulations, such as nasal sprays, tablets, and liquids. They typically work by reducing blood flow to the sinuses, which reduces swelling and opens up the nasal passages.

Dosage recommendations will vary between formulations. For example, adults and children aged over 12 can take two 30 mg tablets every 46 hours and should not exceed eight tablets in a 24-hour period. Side effects can include nervousness, dizziness, and sleeplessness.

Multisystem treatment involves a dual, triple, or quadruple combination of decongestants, analgesics, antihistamines, and expectorants into a single medication. This can be useful for taking and keeping track of a single product.

However, it is important for a person to be aware of the active ingredients and be careful if taking additional medicines to avoid an accidental overdose.

Overall, the safety of such multi-ingredient compounds is similar to that of conventional single-ingredient drugs if a person takes them according to the doses on the label.

Influenza is a common respiratory infection that can affect people of any age. Several treatment options are available to either prevent the condition or help relieve symptoms. It is highly advisable for people to receive their flu shots to reduce the risk of seasonal flu.

Medications such as antivirals, analgesics, antitussives, expectorants, and decongestants can help lessen symptoms and speed up recovery.