What are antivirals for flu (influenza) and COVID-19?

Antivirals are prescription medicines that treat viral infections. There are different antivirals that treat specific viral infections, including the flu (influenza) and COVID-19.

Antivirals can reduce your risk of:

• becoming very sick and experiencing complications
• needing to go to hospital for care
• spreading your illness to other people

If you have a mild infection and are otherwise healthy, you may not need antivirals. Your immune system can often fight your infection on its own. If you are at higher risk of complications (for example, if you have other health conditions) or if you develop severe symptoms, your doctor may prescribe antivirals.

Antivirals are not the same as antibiotics. Learn about the difference between bacterial and viral infections.

Read more about medicines for colds, flu and COVID-19.

How do antivirals for flu and COVID-19 work?

Antivirals work by preventing viruses from infecting healthy cells in your body and multiplying. There are many ways antivirals do this. Each type of antiviral works in its own way.

For example, some antivirals for the flu work by preventing the influenza virus from spreading between your cells. Some COVID-19 antivirals work by preventing the COVID-19 virus from replicating (making copies of themselves).

By slowing down how quickly the virus spreads or replicates, antivirals give your immune system more time to respond. This helps prevent serious complications and death. Antivirals work best when you start taking them within the first 48 hours of developing flu symptoms or within 5 days of developing COVID-19 symptoms.

What types of antivirals might I be prescribed?

If you have the flu, your doctor may prescribe you one of these antivirals:

• oseltamivir, oral capsules (brand name, Tamiflu)
• baloxavir, oral capsules (brand name, Xofluza)
• zanamivir, an inhalation you take in a puffer (brand name, Relenza)
• peramivir, an intravenous (IV) infusion you take as a drip in your vein (brand name, Rapivab)

Flu antivirals are not included on the Pharmaceutical Benefits Scheme (PBS). This means that their cost is not paid in part by the Australian Government.

If you have COVID-19, your doctor may prescribe you one of these antivirals:

• remdesivir, an IV infusion (brand name, Veklury)
• nirmatrelvir and ritonavir, oral tablets (brand name, Paxlovid)
• molnupiravir, oral capsules (brand name, Lagevrio)

There are strict guidelines that help doctors decide if you are eligible for PBS-funded COVID-19 antivirals. You will be eligible if you are:

• over 70 years of age
• over 50 years of age and have 2 or more risk factors for severe disease
• over 30 years of age and are an Aboriginal and/or Torres Strait Islander person and have one risk factor for severe disease
• over 18 years of age and are moderately or severely immunocompromised, or have previously been in hospital with COVID-19 and have now been re-infected

Antivirals for COVID-19 are generally not given to children under 18 years old. Different hospitals may also have their own guidelines for antiviral medicines, based on the rules in their local health network.

What are the side effects or risks of antivirals for flu and COVID-19?

Like all medicines, antivirals have some known possible side effects. Possible side effects of antivirals include:

• nausea and vomiting
• headaches
• hallucinations and delirium
• changes to your sense of taste
• an increase in your liver enzymes
• allergic reaction — rash, serious skin reactions or anaphylaxis

Generally, you can safely take antivirals for the flu if you are pregnant or breastfeeding. Let your doctor know if you are pregnant or breastfeeding so that they can confirm if the specific antiviral you are using is safe for you and your baby.

There are some risks with taking COVID-19 antivirals, and your doctor will discuss these with you. This can help you make an informed decision about taking them.

These risks include:

• Some antivirals that treat COVID-19 can affect your kidneys and liver. If your kidneys or liver aren’t working properly, these medicines might not be suitable. Your doctor will check how your kidneys and liver are working before prescribing these medicines.
• if you are in your reproductive years and are sexually active, your healthcare team can recommend effective contraception for you while you’re taking antivirals for COVID-19. If you are male and taking Lagevrio, it’s important that you use a barrier method of contraception for 3 months after taking this medicine.
• If you are pregnant or breastfeeding, ask your doctor if the antiviral is safe for you and your baby. Before your doctor prescribes a medicine, be sure to tell them if you are pregnant or breastfeeding.

When should I see my doctor?

See your doctor if you have symptoms of the flu or COVID-19, or you have tested positive for the flu or COVID-19. This is especially important if you are at high risk of developing a severe infection — for example, if you also have another health condition. Antiviral medicines work best when started within 48 hours of developing symptoms.

You may be at a higher risk of a severe flu or COVID-19 infection if you are living with a medical condition that affects how well your immune system can protect you, including:

• HIV (human immunodeficiency virus)
• cancer
• chronic diseases — lung disease, kidney disease, heart disease, neurological (nerve) disease or diabetes
• obesity
• some chromosome conditions, for example Down syndrome

Other factors that can also put you at a higher risk of developing a severe infection, include if you:

• have a severe flu infection — especially if you are 65 years or older
• are younger than 5 years old, or were born preterm
• are pregnant or if you have given birth within the past 2 weeks
• belong to an Aboriginal and/or Torres Strait Islander community
• live in a long-term or an aged-care residential facility

If one or more of these apply to you, speak with your doctor even when you are healthy. This way, you can have an action plan in place in case you get sick with the flu or COVID-19.

Are there any alternatives to antivirals?

While antiviral medicines help prevent serious illness and hospitalisation from the flu or COVID-19, there are also other ways to protect yourself. Avoiding illness is always better than getting sick and needing treatment.

Here are some ways you can help prevent the flu or COVID-19:

• Get your flu and COVID-19 vaccines to protect against catching and spreading these viruses.
• Wash your hands well and often.
• Keep your distance from others if you’re unwell; stay away from people who have symptoms of infection.

Medicines are also available to help treat some of your flu and COVID-19 symptoms.

Read more about:

• flu vaccine FAQs
• COVID-19 vaccine FAQs
• preventing COVID-19

Resources and support

• Learn more about COVID-19 antiviral medicines on the NSW Government website.
• Read about preventing, diagnosing and treating the flu on the Australian Government Department of Health, Disability and Ageing website.
• Watch the No Germs on Me video on hand washing by the Menzies School of Health Research.

You can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.

Languages other than English

Queensland Health has resources about COVID-19 translated into community languages.