During every influenza season, many people in Hong Kong consider getting the influenza vaccine to boost immunity and prevent infection. The World Health Organization (WHO) recommends the use of the trivalent influenza vaccine for the Northern Hemisphere in 2025–2026. What does this mean? Can the trivalent vaccine effectively protect us? This article will provide you with updated information on influenza, explain the reasons behind the change in vaccines, and address common questions to help you make informed health decisions. 

Influenza (commonly known as "the flu") is an acute infectious respiratory illness caused by the influenza virus. The virus is mainly transmitted through respiratory droplets, and the incubation period is generally 1 to 4 days. 

• Influenza A virus subtype H1N1 

• Influenza A virus subtype H3N2 
• Influenza B virus

• Winter peak: January to March or April

• Summer peak: July to August
  

Common symptoms of influenza include: 

• Fever 

• Sore throat 

• Cough
  

• Runny nose 

• Headache 

• Muscle aches

• Fatigue 

• Vomiting 

• Diarrhea 

Most influenza patients recover on their own within 2 to 7 days. However, immunocompromised people and the elderly may develop more severe illness after contracting influenza, which can lead to complications such as bronchitis, pneumonia, or encephalopathy, and in severe cases, can be fatal. It is important to note that even healthy individuals may develop severe infections or complications from influenza. 

• Patients with mild symptoms (healthy, low-risk individuals): Ensure adequate rest and maintain good fluid intake. Antipyretics and analgesics (e.g. paracetamol) may be used to relieve fever and body pain as needed. Most will recover on their own without specific treatment.
• High-risk patients (elderly, young children, pregnant women, those with chronic illnesses): Early antiviral treatment should be offered as soon as possible, ideally within 48 hours of symptom onset, even if symptoms appear mild. Do not wait for deterioration. Doctors may prescribe oseltamivir (Tamiflu) or baloxavir (Xofluza) to alleviate symptoms and shorten the duration of illness. Note: baloxavir is not recommended in pregnancy; oseltamivir is preferred.

• Patients with persistent or worsening symptoms: Seek medical attention promptly. Antiviral medications may be prescribed where clinically indicated.
  

According to the Centre for Health Protection, during the influenza peak season at the beginning of the year, there were 199 cases of influenza in Hong Kong requiring admission to intensive care units (ICU) or resulting in death. Over 70% of these severe cases had not received the seasonal influenza vaccine.

In fact, the influenza vaccine can safely and effectively prevent seasonal influenza and its complications, reducing the risk of hospitalisation or death. 

Wash your hands frequently, wear masks properly, cover your mouth and nose with a tissue when sneezing or coughing etc.

Regularly clean and disinfect frequently touched surfaces, keep indoor air well-ventilated, and avoid crowded or poorly ventilated public places. 

The World Health Organization (WHO) recommends the composition of influenza vaccine strains each year based on global virus trends. For the 2025–2026 season, WHO recommends the use of the trivalent vaccine for the Northern Hemisphere. In the 2026–2027 flu season, WHO continues to recommend trivalent vaccines.

Since March 2020, the influenza B/Yamagata lineage virus has not been detected worldwide, indicating that the risk of infection with the B/Yamagata strain is extremely low and it no longer needs to be included in the vaccine. Therefore, it is recommended that all influenza vaccines exclude this component as soon as possible. 

The difference between trivalent and quadrivalent influenza vaccines lies in the number of influenza virus strains they cover. 

• Trivalent (3-component) vaccine: Two influenza A strains and one influenza B strain. 

• Quadrivalent (4-component) vaccine: Two influenza A strains and two influenza B strains. 

Yes, it is. The effectiveness of the vaccine depends on how well the circulating strains match the antigens in the vaccine. The trivalent vaccine provides sufficient protection and effectively prevents the currently circulating strains. 

Priority groups: 

• Healthcare workers 

• People aged 50 or above 

• Pregnant women 

• Residents of care homes 

• People with chronic health conditions 

• Children and adolescents aged 6 months to under 18 years (or students aged 18 or above attending secondary schools in Hong Kong) 

• Poultry industry workers 
• People working in pig farming and slaughtering 
  
  

OT&P Healthcare clinics also provide influenza vaccination services. Our available vaccines this season are sourced from Germany, France, and the Netherlands. 

Although influenza is common, its complications should not be underestimated. For the 2025–2026 season, the influenza vaccine formula has been changed to trivalent due to virus trends. The trivalent vaccine is sufficient to protect against the currently circulating strains, so there is no need for excessive concern. Get the influenza vaccine every year to protect yourself and your community. Our available vaccines this season are sourced from Germany, France, and the Netherlands. If you have any questions, consult our doctor for professional advice.

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