Navigating Flu Vaccines: A Guide for Hong Kong’s Settings

In Hong Kong, where seasonal flu outbreaks are a recurring concern, understanding flu vaccines is crucial for maintaining public health. At OT&P clinic, you can access a range of flu vaccines, including the “Fluarix Tetra”, “Influvac Tetra ”, and “Vaxigrip Tetra” options, all classified as inactivated influenza vaccines (IIV). We will also be prescribing intranasal flu vaccines (administered as nasal spray or mist) classified as live attenuated influenza vaccines (LAIV), a pain-free option for children, which will be available soon. This blog post will explore their effectiveness, the recommended vaccination groups, and essential considerations for individuals in Hong Kong who are considering flu vaccination. 

Summary of Global and Local Influenza Activity

According to the World Health Organization (WHO), influenza activity has been reported globally, with influenza A viruses being the most common. Specifically, A(H1N1) and A(H3N2) strains have been prevalent. In Hong Kong, the 2023-2024 winter influenza season saw a notable increase in cases starting from the second week of January, with a peak in early February. Although the activity decreased slightly in late February, it remained elevated in early March. 

Unpacking the Flu Vaccines 

OT&P currently offers Fluarix Tetra vaccines, Influvac Tetra vaccines, and Vaxigrip Tetra vaccines: 

1. All vaccines provide coverage for two strains of influenza A (H1N1 and H3N2) as well as two strains of influenza B. 
2. All contain inactivated strains of influenza viruses tailored for the Northern Hemisphere. 
3. The formulation of each vaccine aims to provide protection against specific flu strains endorsed by the World Health Organization (WHO) and the European Union (EU) for the 2024/2025 flu season. 
4. All three vaccines are typically approved for individuals aged 6 months and older, including healthy persons and pregnant women.  

Key Considerations in the Hong Kong Setting 

The Scientific Committee on Vaccine Preventable Diseases (SCVPD) recommends the following for the 2024-2025 season: 

1. Vaccination Timing: It is best to get vaccinated early in the season, preferably by September or October, to ensure protection throughout the winter and summer peaks. 
2. Vaccine Components: The quadrivalent vaccine is advised, which covers two strains of influenza A (H1N1 and H3N2) and two strains of influenza B. Flu vaccines are particularly crucial for high- risk groups, including healthcare workers, elderly individuals, pregnant women, residents of residential care homes, and those with chronic medical conditions. More information about flu shots in Hong Kong can be found on our vaccine page. 
3. Children’s Vaccination: Children aged six months to eight years who have not previously been vaccinated require two doses, administered four weeks apart. Those who have been vaccinated previously need only one dose.  
4. Side Effects and Precautions: Being aware of possible side effects post-vaccination, and consulting healthcare providers in case of any concerns or adverse reactions. Of note, people who have had severe allergic/hypersensitivity reactions to flu vaccines and/or its components should defer vaccination and seek advice from medical professionals first. 

Prevention 

The flu vaccine helps protect against the four influenza viruses that research indicates are most common during the upcoming season. It can help prevent you from getting sick with the flu. If you get sick, getting the vaccine reduces the severity of illness and lowers the risk of flu-associated hospitalisation. A 2021 study showed that among vaccinated patients who were admitted to the hospital with influenza, 26% had lower risk of intensive care admissions and 31% had low risk of death from flu compared to the unvaccinated. 

The flu shot is a beneficial preventive tool for people with chronic health conditions. Even if you are healthy, getting the vaccine is an important way of protecting yourself and your loved ones who may be more vulnerable. During pregnancy, it helps protect pregnant women and after pregnancy it confers protection to the infants from flu in their first few months of life. 

As we enter the peak of seasonal influenza, the risk of transmission will get higher and appropriate prevention is important. The Centers for Disease Control and Prevention (CDC) recommends that in the absence of contraindications, all persons aged 6 months and above should receive the influenza vaccine annually.  

If you have any questions or concerns regarding the flu vaccine, consult your healthcare provider for personalised advice and support. 

Reference

1. Grohskopf, L.A. Centers for Disease Control and Prevention. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices – United States, 2024-2025 Influenza Season. 28 August 2024 Retrieved from https://doi.org/10.15585/mmwr.rr7305a1 
2. Centre for Health Protection. Recommendations on Seasonal Influenza Vaccination for the 2024-2025 Season in Hong Kong. 28 August 2024 Retrieved from https://www.chp.gov.hk/files/pdf/recommendations_on_seasonal_influenza_vaccination_for_the_2024_25_season_in_hong_kong_21mar.pdf 
3. Centers for Disease Control and Prevention. Seasonal Flu Vaccines. 28 August 2024 Retrieved from https://www.cdc.gov/flu/prevent/flushot.htm 
4. Centre for Health Protection. Seasonal Influenza. 28 August 2024 Retrieved from https://www.chp.gov.hk/en/healthtopics/content/24/29.html