Flu Vaccine: Why You Need It Every Year, Especially After 60

Many people think flu is just a bad cold. But in older people, flu can be the start of pneumonia, heart failure or illness that keeps them from getting up and walking for weeks. So I often tell the sons and daughters who bring their parents to see me that a flu vaccine once a year is one of the cheapest yet most worthwhile gifts you can give.

How is flu different from a common cold?

Flu is caused by influenza A and B viruses. It usually starts suddenly with high fever, chills, severe body aches, headache, cough and marked tiredness. A common cold, by contrast, usually causes a runny nose, sneezing and a sore throat, and rarely a high fever.

Important complications include viral pneumonia or secondary bacterial pneumonia, flare-ups of chronic conditions such as heart failure, asthma, emphysema and uncontrolled diabetes, and an increased risk of heart attack or stroke in the period after infection.

Why do I need it every year?

1. The virus keeps changing. The World Health Organization announces the vaccine strains every year based on global surveillance data.
2. Immunity falls within several months of vaccination, especially in older people.

Since the 2024 season, the World Health Organization has recommended trivalent (3-strain) vaccines, because the B/Yamagata strain is no longer found circulating. Trivalent vaccines are therefore not inferior to quadrivalent (4-strain) vaccines today.

When to get vaccinated in Thailand

Flu can spread all year round in Thailand, but it usually peaks in the rainy season (about June to September), with a winter wave in some years. Ministry of Public Health campaigns therefore usually start between May and August. Immunity is fully established about 2 weeks after vaccination. If you miss the campaign period, you can still be vaccinated, which is better than not at all. People travelling to the other hemisphere during its winter should also be vaccinated before they go; see Travel health.

1. May–Aug
   Vaccination campaign period

   Get it before or at the start of the flu season

2. 2 weeks after
   Full protection

   About 2 weeks after the shot

3. Jun–Sep
   Rainy season, peak spread

   Most cases in Thailand occur now

4. Cool season
   A second wave is possible

   If you missed the campaign, still get it; better than none

Protection fades within months and strains change each year, hence a yearly shot.

Who benefits most, and who gets it free

Everyone aged 6 months and over can be vaccinated, but the Thai government provides free vaccine during the annual campaign for 7 high-risk groups (under Thai public health coverage):

• Older adults aged 65 and over
• People with chronic diseases, such as COPD, asthma, heart disease, stroke, kidney failure, cancer patients receiving chemotherapy, and diabetes
• Pregnant women from 4 months of pregnancy
• Children aged 6 months to 2 years
• People with cerebral disabilities who cannot care for themselves
• People with thalassemia and people with weakened immunity, including people with symptomatic HIV
• People with severe obesity (weight over 100 kg or BMI of 35 or more)

Details and timing may change each year, so check with the hospital where you are registered. People aged 60–64 who are not in the groups above should also be vaccinated. Expats and visitors can get the vaccine at private clinics and hospitals.

By age

• Adults 65 and over
• Children 6 months–2 years

Chronic disease

• Lung, asthma, heart
• Stroke, kidney failure, diabetes
• Cancer on chemotherapy

Pregnancy

• From 4 months of pregnancy

Weak immunity

• Thalassemia
• Symptomatic HIV immune deficiency

Brain disability

• Unable to care for themselves

Severe obesity

• Weight > 100 kg or BMI ≥ 35

Details may change each year. Check with your hospital for your entitlement.

Vaccines for older adults: which type is best?

The immune system of older people responds less strongly to vaccines, so there are vaccines designed for this group.

ACIP guidance recommends that people aged 65 and over preferably receive a high-dose, adjuvanted or recombinant vaccine, if available. However, a large Danish study in 2025 (DANFLU-2) found that the additional benefit of the high-dose vaccine on hospital admissions may be smaller than expected. The practical conclusion: if a special type isn't available, get the standard vaccine right away. Don't wait.

Side effects and myths

• Possible symptoms: pain and swelling at the injection site, low fever and aches for 1–2 days
• The injected vaccine contains no live virus, so it cannot give you flu. If you get sick after vaccination, it's usually another cold virus, or an infection caught before immunity developed.
• Most people with egg allergy can be vaccinated; even those with a history of severe reactions can be vaccinated in a facility equipped to manage them
• People who have had a severe allergic reaction to a flu vaccine shouldn't have it again, and people who developed Guillain-Barré syndrome within 6 weeks of a flu vaccine should talk to their doctor
• It can be given with the pneumococcal vaccine, shingles vaccine or COVID vaccine, in different arms

Benefits beyond preventing flu

Besides reducing severe illness, the flu vaccine reduces cardiovascular events in people with heart disease. The IAMI study found that vaccination after a heart attack reduced deaths and repeat cardiac events. Vaccinating everyone at home also protects older people and babies with lower immunity, which is at the heart of family medicine care.

When to see a doctor

If you get flu, older adults, pregnant women and people with chronic diseases should see a doctor within the first 48 hours, because antiviral medicine works best when started early. Go to hospital immediately if there is breathlessness, chest pain, drowsiness, confusion, blue lips, a high fever that doesn't come down for more than 3 days, or symptoms that improve and then get worse again. In Thailand, call 1669 for medical emergencies.

At Dr. Kris Clinic I can review adult and senior vaccines for the whole family, recommend the right vaccine type and plan it together with the care of chronic conditions. English-speaking consultations are available. See other recommended checks in Health checkups for working-age adults.