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November 7, 2023

Flu 101: What to Know About Virus Strains and the Vaccine with Nicole Drobner, PA

by Nicole Taylor Drobner, PA

Influenza, or the flu, is a highly contagious respiratory illness that affects millions of people worldwide every year. Understanding the flu and the vaccines designed to prevent it is essential for staying healthy during flu season. In this comprehensive guide, we’ll explore the basics of flu virus strains and the importance of the flu vaccine.

What is Influenza?

Influenza is a viral infection caused by various strains of influenza viruses. It’s different from the common cold, often presenting with more severe symptoms. The flu can lead to complications like pneumonia and, in some cases, can be life-threatening. Understanding the flu starts with knowing about the different virus strains that circulate.

Flu Virus Strains

Influenza viruses are constantly evolving and mutating, which is why updated flu vaccines are needed each year. There are three main types of influenza viruses: Influenza A, Influenza B, and Influenza C. Influenza A and B are the primary culprits behind seasonal flu outbreaks.

Influenza A

Influenza A viruses are divided into subtypes based on two proteins on their surface: hemagglutinin (H) and neuraminidase (N). There are multiple H and N subtypes, resulting in various combinations. The most common influenza A subtypes responsible for seasonal flu in humans are H1N1 and H3N2.

Influenza B

Influenza B viruses are classified into two lineages: B/Victoria and B/Yamagata. Both lineages can co-circulate during a flu season, making it challenging to predict which one will predominate. This unpredictability is one reason why flu vaccines are updated annually.

Influenza C

Influenza C viruses typically cause mild respiratory infections and are less common than Influenza A and B. They do not cause seasonal flu epidemics.

Seasonal Flu Vaccines

The flu vaccine is the most effective way to prevent the flu and its complications. It works by exposing your immune system to a harmless piece of the virus, stimulating an immune response without causing illness. This allows your body to effectively create its own antibodies in order to fight off future infections! Here’s what you need to know about the flu vaccine:

Annual Updates

Because flu viruses mutate and evolve over time, the composition of the flu vaccine changes each year to match the most prevalent strains based on current data. This is why it’s essential to get a new flu shot annually, preferably before or right at the start of flu season.

Flu Shot vs. Flu Mist

Flu vaccines come in two main forms: injectable (flu shot) and nasal spray (flu mist). Both are effective, but some vaccines are recommended based on age and health status. Consult with your healthcare provider to determine the best option for you.

Herd Immunity

Getting a flu vaccine not only protects you but also contributes to herd immunity. Herd immunity occurs when a sufficient percentage of the population is vaccinated. Without human hosts, the virus is unable to spread, protecting those who cannot be vaccinated such as infants and people with certain medical conditions. Herd immunity has proven to be effective in virtually eliminating various deadly illness in the past, such as smallpox, measles, mumps, rubella, polio, chickenpox, etc.

Side Effects

Common side effects of the flu vaccine include soreness at the injection site, mild fever, and fatigue. Serious side effects are rare. The benefits of vaccination far outweigh the risks, especially for those in high-risk groups.


One should beware of misconceptions when considering getting the flu shot. For instance, the influenza vaccine does not cause the flu. In fact, the most commonly used flu vaccines contain a completely inactivated virus particle. As mentioned above, it is possible to experience symptoms related to your immune system creating a response to the vaccine. Additionally, while flu vaccines are created using egg product, the final flu vaccine has only trace egg protein remaining. According to the CDC, this makes the flu shot safe, even for those with known allergy to egg. If you have ever experienced an adverse reaction to a vaccine, or if you have an allergy to egg, you should discuss this with your healthcare provider.


The effectiveness of the flu vaccine can vary from year to year, primarily due to the match between the vaccine strains and the circulating flu strains. Because of this, it is possible to get the flu while vaccinated. However, even when the vaccine isn’t a perfect match, it can reduce the severity of symptoms and the risk of complications.

Who Should Get Vaccinated?

The Centers for Disease Control and Prevention (CDC) recommends flu vaccination for everyone six months of age and older, with rare exceptions. High-risk groups, including the elderly, young children, pregnant women, and individuals with certain medical conditions, are strongly encouraged to get vaccinated.

The Importance of Flu Vaccination

Getting vaccinated against the flu offers numerous benefits, both for individuals and communities. Here are some key reasons to prioritize your annual flu shot:

Preventing Illness

The primary goal of the flu vaccine is to prevent illness. By getting vaccinated, you significantly reduce your risk of contracting and spreading the flu to others.

Reducing Hospitalizations

Flu vaccination has been shown to reduce the number of flu-related hospitalizations. It can help ease the burden on healthcare systems, especially during severe flu seasons.

Protecting Vulnerable Populations

Vaccination is crucial for protecting vulnerable populations like the elderly, young children, and individuals with weakened immune systems. It helps shield those who are at higher risk of severe flu-related complications. You may be at higher risk if you have been diagnosed with Diabetes Mellitus, Asthma, COPD, heart disease, obesity, HIV, autoimmune disease, if you have cancer or are being treated with medications that suppress the immune system, or if you are living in a group home, assisted living, or other care facilities.

Combatting the Spread of Flu

By getting vaccinated, you contribute to herd immunity, making it more challenging for the flu virus to spread in your community. This is especially important for protecting those who cannot receive the vaccine.

Minimizing Economic Impact

Flu outbreaks can have a significant economic impact due to increased healthcare costs and lost productivity. Widespread vaccination can help mitigate these effects.

Understanding the flu and the importance of the flu vaccine is crucial for staying healthy during flu season. Influenza is a constantly evolving virus, with different strains circulating each year. The flu vaccine, which is updated annually, is the most effective way to prevent the flu and its complications. It offers individual protection and contributes to the well-being of the entire community, particularly those at higher risk.

Make it a priority to get your annual flu shot, consult with your Avance Care primary care provider for guidance, and stay informed about the latest recommendations. With the right knowledge and proactive measures, you can reduce your risk of contracting the flu and help protect those around you. Stay healthy, stay informed, and get vaccinated to stay ahead of the flu.

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