Latest 2024-2025 Flu Vaccine Recommendation Must Be Know Providers

The annual flu season is a time when many people seek to protect themselves against the flu virus by getting vaccinated.

For the 2024-2025 flu season, a significant recommendation has been made: all U.S. flu vaccines will now be three-component (trivalent) vaccines.

These vaccines will include protection against influenza A(H1N1), A(H3N2), and B/Victoria-lineage viruses.

Notably, the influenza B/Yamagata virus, which was included in previous four-component (quadrivalent) vaccines, is no longer considered necessary for inclusion in this season’s flu vaccines. But why has this change occurred? Let’s break it down.

2024-2025 Flu Vaccine Recommendation

The CDC has issued its recommendations for the updated 2024-2025 flu vaccines:

Key Points

• CDC recommends everyone 6 months of age and older, with rare exceptions, receive an updated 2024-2025 flu vaccine to reduce the risk of influenza and its potentially serious complications this fall and winter.
• Updated 2024-2025 flu vaccines will all be trivalent and will protect against an H1N1, H3N2, and a B/Victoria lineage virus. The composition has been updated with a new influenza A(H3N2) virus compared to last season.
• September and October remain the best times for most people to get vaccinated. Flu vaccination in July and August is not recommended for most people, but there are some considerations for specific groups like pregnant women and children.
• The WHO recommends that trivalent vaccines for use in the 2024-2025 northern hemisphere influenza season contain updated H1N1, H3N2, and B/Victoria lineage virus strains.
• The B/Yamagata lineage vaccine component is being excluded as it is no longer warranted due to its significant decline in circulation globally.

Eligible Groups

The CDC encourages everyone 6 months and older to get vaccinated, with rare exceptions. Some key groups eligible for flu vaccination include:

• Pregnant women
• Children aged 6 months through 18 years
• People 50 years of age and older
• People with certain chronic medical conditions
• Residents of nursing homes and other long-term care facilities
• Health care workers

In summary, the updated 2024-2025 trivalent flu vaccines are now recommended for nearly everyone, with September and October being the optimal time to get vaccinated. The composition has been updated

What are Flu Vaccines?

Flu vaccines are designed to protect against the most common strains of the influenza virus circulating in a given flu season. These vaccines help your immune system recognize and fight off the virus if you are exposed.

Types of Flu Vaccines Available

There are several types of flu vaccines available, each designed to protect against influenza viruses. Here are the main categories:

1. Inactivated Influenza Vaccines (IIV)

• Quadrivalent Inactivated Influenza Vaccine (IIV4): This is the most commonly administered flu vaccine, protecting against four strains of influenza—two A strains and two B strains. It is approved for individuals aged 6 months and older and is typically administered via injection.
• Trivalent Inactivated Influenza Vaccine (IIV3): Historically provided protection against three strains, but it is not available for the 2021-2022 flu season and has largely been replaced by quadrivalent options.

2. Live Attenuated Influenza Vaccine (LAIV)

• Quadrivalent Live Attenuated Influenza Vaccine (LAIV4): This is a nasal spray vaccine made with weakened live viruses. It is approved for use in individuals aged 2 to 49 years and is a good option for those who may be hesitant about needles. However, it is not recommended for pregnant women or individuals with certain medical conditions.

3. Recombinant Influenza Vaccine (RIV)

• Quadrivalent Recombinant Influenza Vaccine (RIV4): This vaccine is produced without using the influenza virus or eggs, making it suitable for individuals with egg allergies. It is approved for adults aged 18 years and older and is one of the preferentially recommended vaccines for seniors.

4. Cell-Cultured Influenza Vaccine

• Quadrivalent Cell-Cultured Influenza Vaccine (ccIIV4): This vaccine is produced using cell culture rather than eggs and is also approved for individuals aged 6 months and older.

5. Vaccines for Seniors

Specific vaccines are recommended for individuals aged 65 years and older to enhance immune response:

• High-Dose Quadrivalent Inactivated Vaccine: Contains four times the antigen compared to standard-dose vaccines.
• Adjuvanted Quadrivalent Inactivated Vaccine: Contains an adjuvant to boost the immune response.

Summary of Flu Vaccine Options:

• Standard-dose IIV4: For ages 6 months and older.
• High-dose IIV4: For seniors, it provides a stronger immune response.
• RIV4: For ages 18 and older, suitable for those with egg allergies.
• LAIV4: Nasal spray for ages 2 to 49, not for pregnant women.
• ccIIV4: Cell-cultured vaccine for ages 6 months and older.

So, Annual flu vaccination is recommended for everyone aged 6 months and older. It’s essential to consult with healthcare providers to determine which vaccine is most appropriate based on age, health status, and potential allergies

What is a Trivalent Flu Vaccine?

Understanding the Three-Component (Trivalent) Vaccine

The trivalent flu vaccine offers protection against three strains of the influenza virus. For the 2024-2025 season, these strains are:

1. Influenza A(H1N1)
2. Influenza A(H3N2)
3. Influenza B/Victoria-lineage

How do Trivalent Vaccines Differ from Quadrivalent Vaccines?

Trivalent and quadrivalent flu vaccines differ primarily in the number of influenza virus strains they protect against. Here’s a detailed comparison:

Trivalent Flu Vaccine

• Composition: The trivalent flu vaccine includes three strains:
  • Two strains of Influenza A (typically H1N1 and H3N2).
  • One strain of Influenza B (usually from the Victoria lineage).
• Protection: It protects against the most common strains expected to circulate in a given flu season. However, having only one B strain means there is a mismatch risk if the circulating B strain is from the Yamagata lineage, which is not covered by this vaccine.
• Usage: Historically, trivalent vaccines have been widely used, but their availability has decreased as quadrivalent vaccines have become more common. Recent recommendations indicate a potential shift back to trivalent formulations due to the decline of the B/Yamagata strain since early 2020

Quadrivalent Flu Vaccine

• Composition: The quadrivalent flu vaccine includes four strains:
  • Two strains of Influenza A (H1N1 and H3N2).
  • Two strains of Influenza B (one from the Victoria lineage and one from the Yamagata lineage).
• Protection: This vaccine offers broader protection by covering both B lineages, reducing the likelihood of a mismatch with circulating strains. This is particularly beneficial given the historical presence of both B strains in the population.
• Usage: Quadrivalent vaccines have been the standard recommendation in recent years due to their increased effectiveness in preventing flu-related complications, especially in seasons with high activity of both B strains. They are now the preferred option in many healthcare settings, although some trivalent formulations may return depending on circulating strains

Summary of Differences:

 

Feature	Trivalent Vaccine (IIV3)	Quadrivalent Vaccine (IIV4)
Strains Covered	2 A strains, 1 B strain	2 A strains, 2 B strains
Risk of Mismatch	Higher (only 1 B strain)	Lower (covers both B strains)
Current Usage	Decreasing, with potential return	Widely used and preferred
Effectiveness	Effective, but less comprehensive	More effective due to broader coverage

to match the influenza strains expected to circulate, while excluding the B/Yamagata lineage.