Figures from the World Health Organization indicate that each year, there are 250,000 – 500,000 deaths worldwide due to influenza. In Thailand, there are approximately 50,000 influenza cases annually, with outbreaks reaching as high as 70,000 cases in epidemic years.
It is well known that influenza patients experience more severe symptoms than those with the common cold, increasing the risk of exacerbation of underlying conditions and complications. These include pneumonia, bronchitis, or severe impacts on the cardiovascular and nervous systems, which can lead to death.
Influenza is caused by the influenza virus, which has three types: A, B, and C. Types A and B are the main causes of acute respiratory infections. The infection usually begins in the upper respiratory tract (nose and throat) and may spread to the lungs and bronchi.
Historically, influenza outbreaks were mainly caused by type A viruses, known as A/H1N1 and A/H3N2, which are the primary strains. However, in recent years, outbreaks of type B viruses have increased worldwide, including in Thailand, where type B outbreaks have risen to 13-55% as well.
Additionally, the severity of the two lineages of type B viruses that co-circulate, Victoria and Yamagata, can lead to hospitalization or death at rates comparable to type A strains.
The best prevention for influenza is vaccination to build immunity. Previously, the trivalent influenza vaccine covered type A/H1N1, A/H3N2, and one lineage of type B virus. Currently, an additional lineage of type B virus has been added to the vaccine, enhancing the effectiveness of influenza virus infection prevention.
Quadrivalent Influenza Vaccine
Since the first isolation of the influenza virus in 1993, influenza vaccines have been continuously developed. In 2012, the World Health Organization (WHO) recommended adding another type B virus strain to the vaccine to improve influenza prevention. This is the Quadrivalent Influenza Vaccine, which covers the following four virus strains:
- Influenza virus type A/H1N1
- Influenza virus type A/H3N2
- Influenza virus type B, Victoria lineage
- Influenza virus type B, Yamagata lineage
WHO Recommended Influenza Vaccines
Studies on the benefits of the quadrivalent influenza vaccine in various countries show that in the UK, the use of the quadrivalent vaccine increased protection against influenza, especially type B, by 18%. In the US, replacing the trivalent vaccine with the quadrivalent vaccine could reduce influenza cases by 1.3 million per year, hospitalizations by 12,472 per year, and deaths by 663 per year. If the quadrivalent vaccine is included in the basic public health program over the next 20 years, it is cost-effective, potentially reducing influenza cases by 13.3 million, hospitalizations by 113,000, and deaths by 13,200. It could also save $31 billion in medical costs and $600 million in other related expenses.
Why get the influenza vaccine every year?
The influenza vaccine should be administered before the epidemic seasons (rainy and winter seasons) and annually, especially for high-risk groups. This is because the immune system’s protection against influenza decreases over time. Annual vaccination boosts immunity to maintain high protection levels. The quadrivalent vaccine is recommended for children from 6 months old to adults and the elderly, including pregnant and breastfeeding women, who can also receive the influenza vaccine.
Groups at risk of influenza infection who should be vaccinated
- Children under 5 years old
- Adults aged 65 years and older
- Pregnant women and women within 2 weeks postpartum
- Patients with chronic diseases requiring ongoing care, such as diabetes, heart disease, lung disease, or liver and kidney disorders
Benefits of the quadrivalent influenza vaccine
In addition to protecting against all four influenza virus strains, the influenza vaccine offers other benefits as follows:
- Provides broader protection against type B influenza virus strains
- Reduces the spread of influenza virus
- Decreases complications from influenza infection, especially in young children and chronic patients
- Reduces antibiotic use due to bacterial complications
- Lowers treatment costs
- Reduces absenteeism from work or school
- Decreases hospitalization rates
- Reduces mortality from influenza
