Respiratory illness season follows a pattern that is hard to read, and it changes from year to year. Influenza, COVID-19, respiratory syncytial virus (RSV), pneumococcal disease, and pertussis can all circulate at the same time, and each one peaks at a different point and carries its own risks. Knowing what that overlap looks like is the first step to protecting yourself and the people you care for.
The season has a pattern, but it is not as predictable as it used to be
Respiratory viruses follow a seasonal rhythm. In Canada, that season typically runs from late October through April, while the Southern Hemisphere experiences its own wave a few months ahead of ours, and often with different strains in circulation. Within that broader window, each virus behaves differently:
- COVID-19 (SARS-CoV-2): Surveillance data from 2023 to 2024 showed elevated case counts even through the summer months, with an upswing in July and August. More recent data from early 2026 continues to reflect that pattern, with wastewater surveillance in several Canadian provinces indicating year-round viral activity rather than a defined seasonal peak. COVID no longer waits for winter.
- Influenza A: Peaks in late October through January, usually hitting its highest point in January.
- Influenza B: Follows a different curve, with a notable bump in April, a time when most people assume flu season is over.
- RSV (respiratory syncytial virus): Climbs through December and January.
- Pertussis (whooping cough): Showing increased incidence in various parts of the world, regardless of season.
Why this matters more than “just a cold”
More than 200 viruses can cause respiratory illness, the most common being rhinoviruses, adenoviruses, seasonal coronaviruses, RSV, influenza, and COVID-19. Bacteria play a role too, including streptococcus, which causes strep throat, ear infections, pneumonia, and pertussis.
Certain groups face higher risk:
- Infants and young children, whose smaller airways swell and fill with mucus more easily during infection.
- Adults over 65, whose immune systems respond less robustly to new threats, a process called immunosenescence.
- People with chronic conditions, including heart disease, diabetes, chronic lung disease, asthma, COPD, and obesity as these conditions can affect immune function and increase the risk of complications from respiratory infections.
- People in close contact with young children, since kids are often less diligent hand-washers and are prone to putting more objects in their mouth. This makes it easier for children to pick up infections at daycare or school and bring them home, increasing the risk of exposure for family members and caregivers.
It is tempting to treat a respiratory infection as a few uncomfortable days and move on. The data suggests a more serious picture, particularly for three illnesses.
Influenza can do more than knock you off your feet for a week. The Public Health Agency of Canada estimates that influenza leads to about 12,200 hospitalizations and 3,500 deaths each year. Complications include sinus and ear infections, pneumonia, and in some cases inflammation of the heart or brain lining. Healthy Canadians under 65 are affected too, though for them serious complications are less likely.
COVID-19 is a long-term concern, not just an acute one. Research suggests that 50 per cent of people with long COVID show damage to at least one organ, and the risk of complications rises with each reinfection. Long COVID means symptoms lasting 90 days or more after infection. Research links even a single infection to arterial stiffness, insulin resistance, and increased rates of hypertension and diabetes.
Respiratory syncytial virus, commonly called RSV, has long been understood as a serious risk for infants, but the picture for adults deserves equal attention. Among adults hospitalized with RSV, mortality rates range from 6 to 13 per cent, depending on age and underlying health conditions. Nearly one in four hospitalized adults experience an acute cardiac event, and those hospitalized with RSV may face a sharply elevated risk of cardiorespiratory events in the weeks that follow.
Prevention starts with the basics
Vaccines work best alongside everyday precautions such as:
- Stay home when sick and keep children home from school when they are symptomatic.
- Improve ventilation indoors, including air purifiers where possible.
- Wash your hands regularly, which helps with droplet transmission.
- Wear a well-fitting N95 or KN95 mask in crowded indoor spaces. Standard surgical masks offer less protection against airborne transmission.
- Cover coughs and sneezes and disinfect frequently touched surfaces.
This is not groundbreaking advice. It is, however, grounded in decades of evidence, and it remains the most reliable layer of protection we have alongside vaccination.
What is available this fall
The following vaccines are expected to be available in Canadian pharmacies and at Harrison clinics starting mid to late October 2026. Note: availability and recommendation may vary by province, clinic, supply, age, indication, and timing.
| Vaccine | Who it is for | Where to get it |
| Updated, annual influenza vaccine (flu) | Everyone six months and older; high-dose options (Fluzone HD) or adjuvanted options (Fluad) recommended for adults 65 and older. Recent head-to-head trials comparing Fluzone HD and Fluad have shown similar efficacy. | Flu vaccines are available at pharmacies, with limited supply at select Harrison Centres for high-risk individuals. Contact your Harrison team to see if there is availability of Fluad or Fluzone HD, or check your local public health center or pharmacy. |
| Updated COVID-19 vaccine (mRNA, targeting KP2, or Novavax, targeting KP2/KP3) | Everyone six months and older, including children | Pharmacy or local public health clinics |
| Arexvy or Abrysvo (RSV) | Adults 60 and older; Abrysvo is also indicated for pregnant patients at 32 to 36 weeks gestation | Arexvy available at all Harrison Centres for adults 60 and older, and Abrysvo for pregnant individuals. |
| Beyfortus (RSV) | Infants under 8 months old entering or during their first RSV season, or shortly after birth if born during the season | All Harrison Centres |
| Prevnar 20 (pneumococcal) | Adults previously vaccinated with older pneumococcal vaccines, particularly if it has been more than one year since Prevnar 13 alone, or more than five years since Prevnar 13 and Pneumovax 23 in series | All Harrison Centres |
| Tdap (tetanus, diphtheria, pertussis) booster | Adults in areas with rising pertussis activity; recommended for pregnant patients in their third trimester | All Harrison Centres |
A word on vaccine hesitancy and some vaccine FAQs
We hear real concerns, and they deserve real answers.
If I had RSV or COVID-19 recently, do I still need the vaccine? Recent infection can provide some temporary immunity, but protection can fade, particularly in older adults and people with chronic conditions, so we don’t recommend relying on “natural immunity” alone. After a confirmed COVID-19 infection, your healthcare provider may advise waiting before your next dose, depending on your vaccination history, timing of infection, and individual risk factors. However, if you are at higher risk, vaccination may still be recommended.
Can I get all these vaccines at once? Flu, COVID-19, and pneumococcal vaccines pair well together. Your care team will usually give vaccines in different injection sites, spaced about an inch apart, and track exactly which vaccine went where.
Do I really need a flu vaccine every year? Influenza viruses evolve from year to year, and vaccines are updated annually to reflect the strains expected to circulate. Protection from previous vaccinations also wanes over time, making annual vaccination an important part of reducing your risk of influenza and its complications.
What we recommend you do next
Talk to your healthcare provider about getting your flu, COVID-19, RSV, and pneumococcal vaccines this fall. Your Harrison team reviews immunization records as part of your annual checkup, but you do not need to wait for that visit. If you are unsure which vaccines you are due for, contact your Care Team and ask them to review your record directly.
Respiratory viruses won’t wait for a convenient time to circulate into your home, office or school this fall, so your protection shouldn’t wait either.
