Is it COVID-19 or the flu? Why you should get vaccinated.

Countries around the world are seeing COVID-19 cases surge after successfully slowing down outbreaks earlier this year. As we scramble to respond to second-waves of infection, an additional challenge is fast approaching: flu season.

Getting your annual flu shot is more important than ever this year. If you haven’t received the vaccine in recent years, this is the year to get it.

In this blog, we answer some common questions about the flu shot and why it’s so important to get vaccinated whether you are travelling or not.

Why is it important to get vaccinated this year?

There are several reasons to get the flu shot this year.

Flu season often takes an enormous toll on healthcare systems. As COVID-19 response efforts continue, the added surge of influenza cases could overwhelm hospitals. The flu vaccine isn’t perfect but getting vaccinated can protect you and others, and reduce the strain on clinics and hospitals.

If you are at high risk of severe flu-related illness, you are also at higher risk of severe COVID-19 infection; this includes older adults and those with pre-existing conditions. Getting vaccinated can help ensure that healthcare resources and hospital beds can be prioritized for people with COVID-19, for which there is currently no vaccine.

Since symptoms of COVID-19 and the flu can be very similar, getting the flu shot may also reduce the amount of COVID-19 testing needed to confirm the illness. If flu infections surge this year, COVID-19 testing centres could be severely overwhelmed which would make it difficult to control the spread of both infections.

Lastly, although there have been many advances in our knowledge about COVID-19 over the past few months, we don’t know how co-infection with COVID-19 and the flu can affect your health. Both illnesses can cause pneumonia and complications affecting the brain, heart and muscles, and researchers suspect that co-infection could increase the risk of long-term effects to those organs.

Who should get the flu shot?

The flu shot is recommended for everyone 6 months of age and older.

Vaccination is especially important for those at high risk of influenza-related complications such as young children, older adults, pregnant women, and people with pre-existing conditions. It is also highly recommended for anyone considering travelling soon.

People over the age of 65 – in addition to being at high risk of complications – are also shown to have a lower immune response after vaccination compared to young people. If you are in this age group, you may be eligible to get a type of flu shot that provides greater protection. Talk to your healthcare practitioner to determine what flu vaccine is right for you.

You should not get the flu vaccine if you have had a severe reaction to a previous flu shot. Discuss your options with your healthcare practitioner.

Will the flu shot increase or decrease my risk of getting COVID-19?

No. Getting the flu shot will not protect you from COVID-19 or increase your risk of infection.

COVID-19 and influenza are caused by different viruses. Vaccines are designed to stimulate immunity to specific viruses. For example, the influenza vaccine triggers immunity to the specific influenza strains that are most prominent this year. As such, it will have no effect on SARS-CoV-2 (the coronavirus that causes the disease COVID-19). An effective COVID-19 vaccine – when it’s developed – would provide protection against SARS-CoV-2.

What are symptoms of the flu?

Flu and COVID-19 symptoms can be very similar and it can be difficult to tell the difference between them based on the signs and symptoms alone. A COVID-19 test can help confirm a COVID-19 diagnosis. If you do not have COVID-19, you may have the flu or another respiratory illness.

The following chart shows the similarities and differences between the flu and COVID-19:

	Influenza (flu)	COVID-19
Symptoms	Fever Chills Cough Stuffy nose Sore throat Muscle aches Headache Fatigue Loss of appetite Sometimes vomiting or diarrhea (especially in children)	Fever Chills Cough Stuffy nose Sore throat Muscle aches Headache Fatigue Loss of appetite Sometimes vomiting or diarrhea (especially in children) Loss of taste or smell
Presentation of illness	Infection can be asymptomatic. Symptoms typically appear 1-4 days after infection. People are contagious for 3-4 days after their illness begins.	Infection can be asymptomatic. Symptoms typically develop 5 days after infection but can appear as early as 2 days or as late as 14 days after infection. It is estimated that you can be contagious for up to 10 days, but more research is needed.
Severity of illness	Mild to severe illness. Risk of complications is higher for young children and older persons.	Mild to severe illness. Causes more severe illness in high risk populations (people 65 years of age and older and those with pre-existing conditions) than the flu. Mortality rates are still being estimated but are thought to be substantially higher (possibly 10 times or more) than the flu.
Recovery time and complications	People generally recover within 7-10 days. Complications such as pneumonia, respiratory failure, and others can occur.	Mild cases typically recover in 2 weeks; severe cases can take up to 6 weeks. Complications are similar to those from the flu but can also include long-term damage to the lungs, heart, kidneys, brain and other organs. In rare cases, children can be infected with Multisystem Inflammatory Syndrome in Children (MIS-C).

(Chart information adapted from: CDC)

In addition to the flu shot, what are other ways I can prevent and avoid spreading the flu?

Many of the measures in place to reduce COVID-19 transmission can also aid in limiting flu transmission. In the Southern hemisphere, for example, flu season is just ending and confirmed influenza cases have been unusually low due to physical distancing and wearing masks.

In addition to getting your annual flu shot, you can further reduce influenza transmission by doing the following:

Wash your hands often with soap and water. If soap and water are not available, use a hand sanitizer with at least 60% alcohol.
Cover your mouth when you cough or sneeze. Cough/sneeze into the crook of your elbow or a tissue. Make sure to safely discard the tissue immediately after use.
Avoid touching your face. The virus can enter your body through your mouth, nose, or eyes.
Clean high-touch surfaces often. Viruses, such as the flu, can live for up to 48 hours on surfaces like countertops, phone screens, and door handles.
Stay at home if you are sick. The best way to avoid spreading the flu is to reduce your contact with others, especially those who are vulnerable to severe infection such as people over 65, children under 5 (particularly children under 6 months who are too young to get the flu shot), pregnant women, and those with immune-suppressive health conditions. Aside from visiting your healthcare practitioner, avoid going to public places, work, or school.

Why do I have to get a flu shot every year?

Every year there are many strains of the flu, some of which are new and others that are mutations of existing strains. This means that last year’s flu vaccine can be less effective or completely ineffective against the strains circulating this year.

It’s also important to get vaccinated every year because your immune protection from vaccination declines over time. Getting vaccinated every year allows your body to have optimal protection against this year’s flu season.

How the flu vaccine works

The influenza virus is highly skilled at mutating to trick the immune system. When you get a flu shot, the vaccine uses an inactivated and harmless version of a flu strain to trigger a reaction from your immune system. In defense, your immune system will produce antibodies to protect you from the virus in the vaccine. If you later become exposed to the flu, your body will be able to recognize the strain it was vaccinated against and has already built the antibodies to protect you.

Why did I get sick even though I got the flu shot?

There are a number of reasons why people can still get sick after getting the flu vaccine. The flu vaccine does not give you the flu or any other respiratory disease. However, even if you get vaccinated you may develop flu-like symptoms for a variety of reasons, including:

You were infected before the flu vaccine took effect. It takes approximately two weeks to build up immunity after vaccination. If you were exposed to influenza shortly before you were vaccinated or during the two week period before immunity is established, you can be infected.
The influenza strains in the vaccine do not match the strain you were exposed to. Every year, scientists develop a new flu vaccine based on years of extensive global data. The vaccine targets – what scientists estimate to be – the most prominent strains of flu in circulation this year. However, you can be infected if you are exposed to a strain that wasn’t included in this year’s vaccine.
You may experience a reaction to the flu vaccine as your body produces protective antibodies. Some people report mild reactions such as muscle aches, headaches, and a low-grade fever, lasting 1-2 days post-vaccination.
You may have another illness. The common cold, among many other respiratory illnesses, can cause flu-like symptoms. You may have symptoms of the flu but have a different illness.

Resources

Call your healthcare practitioner or pharmacist to get your flu shot. For more information on COVID-19 and the flu, check out these resources:

Frequently Asked Influenza (Flu) Questions: 2020-2021 Season – CDC

Flu vaccines work – CDC

Flu (influenza): Get your flu shot – Health Canada

Influenza Vaccines for the 2020–2021 Influenza Season – Public Health Ontario