Differential Diagnosis: Influenza vs. the Common Cold


It’s that time of year! Pharmacies across Canada will be receiving large shipments of the influenza vaccine. In fact, any individual can walk into a pharmacy that participates in the Universal Influenza Immunization Program (UIIP) and receive their influenza vaccine with no appointment necessary, making it very convenient and accessible.

Unfortunately there are often misconceptions regarding the flu that hinders people’s ability to receive the vaccine. The most prevalent myth is patients who claim they got sick after receiving the flu vaccine, and therefore trying to claim that the vaccine itself is ineffective.

What pharmacists must educate their patients about is that it is still possible to get flu-like symptoms after receiving the flu vaccine but they cannot contract the flu from the vaccine and these side effects are usually seen in the few days after receiving the vaccine and are short-lived and not severe in nature. There is also the chance that patients may actually be contracting the common cold virus and mistakenly assuming they have come down with the flu.

There is often this misunderstanding around the differences between influenza and the common cold, which may result in public perception that the flu vaccine is ineffective or that is causes people to end up getting the flu.


Interesting fact: the flu is actually the most common vaccine-preventable illness in Canada. The virus commonly spreads from one individual to another through the transmission of respiratory droplets. What this means is when someone coughs or sneezes, the flu can be spread to other people who are within close proximity to the infected individual. It is also common for the flu to spread when someone coughs or sneezes into their own hands and then end up spreading those germs by shaking hands with another person or touching other surfaces that other people come in contact with.

In most cases, uncomplicated influenza typically resolves after 3-7 days, but can persist for more than 2 weeks. According to Health Canada guidelines, everyone 6 months and older should be vaccinated each year to keep them safe from the flu.

In addition, women who are pregnant are at a higher risk for severe diseases and complications so this patient population should be vaccinated. Other individuals with underlying health issues or comorbidities such as asthma, diabetes or chronic obstructive pulmonary diseases should always get vaccinated.

Flu Symptoms

  • Constant Headaches
  • Severe Aches and Pains
  • Muscle Soreness
  • Chills
  • Severe Couch
  • Extreme Exhaustion
  • Fatigue
  • Sneezing/Stuffy Nose
  • Sore Throat

Common Cold

According to Health Canada, the common cold tends to affect 1 billion people annually. The common cold can also be contracted when inhaling or touching contaminated surfaces. Currently, there is no vaccination or cure for the common cold, but symptoms typically begin 2-3 days after transmission and can last up to 2 weeks. If an individual does contract the cold the only thing they can do is try to get plenty of rest, drink lots of fluids, and use OTC products to help alleviate symptoms. People can prevent the common cold by practicing good hand hygiene practices.

Cold Symptoms

  • Sore Throat
  • Aches and Pains
  • Light Fever
  • Mild Fatigue
  • Sporadic Headaches
  • Mild Cough
  • Sneezing/stuffy/runny nose


Health Canada