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Influenza remains a serious health problem in Thailand. In the first eight months of 2025 alone, more than 460,000 cases and 53 deaths were reported. Vaccination continues to be the most effective way to reduce illness, hospitalizations and mortality.
New vaccine option: The Live Attenuated Influenza Vaccine (LAIV), given as a nasal spray instead of an injection, is now available for individuals aged 2–49 years.It has been used globally for over two decades, with more than 200 million doses administered.
Proven efficacy: Clinical data demonstrate up to 88% effectiveness in children and adolescents, with a 63% reduction in hospitalization and immunity lasting for up to 12 months.
Dual immune protection: Unlike the traditional flu shot, LAIV stimulates immunity in both the respiratory mucosa and systemic circulation.
Needle-free and well tolerated: The vaccine is safe and convenient, especially for those who fear injections. Mild, temporary nasal congestion or runny nose are the most common side effects.

Influenza: A Continuing Concern

Influenza is a common respiratory viral infection that can affect individuals of all ages and may cause serious complications.
In Thailand, influenza occurs year-round, with increased incidence during the rainy and winter seasons.
According to the Department of Disease Control (DDC), between January and August 2025, there were 464,891 reported cases, equivalent to 716.18 cases per 100,000 population, and 53 fatalities (case fatality rate: 0.011%).
Currently, approximately 10,000 new cases are being reported weekly.

Annual vaccination remains the most effective strategy to reduce infection rates, hospitalizations and deaths associated with influenza.

What Is the Nasal Spray Influenza Vaccine?

The nasal spray influenza vaccine is a Live Attenuated Influenza Vaccine (LAIV) that contains weakened influenza viruses. These viruses cannot cause illness but effectively stimulate the immune system to develop protection against influenza.
Unlike traditional injectable vaccines, LAIV is administered as a nasal spray rather than a muscle injection.
Important: The vaccine must be prescribed and administered by a doctor or pediatrician and is not available for self-administration or over-the-counter purchase.

Who Can Receive It?

The nasal spray influenza vaccine is recommended for healthy individuals aged 2 to 49 years.

Effectiveness of the Nasal Spray Vaccine

With over 20 years of global use and more than 200 million doses administered, LAIV has demonstrated excellent safety and efficacy profiles.

Key benefits include:

Needle-free administration: Delivered as a nasal spray, making it more appealing, especially for children or individuals with needle anxiety.
High efficacy: Provides up to 88% protection in children and adolescents. Compared with traditional inactivated flu vaccines (TIV), LAIV shows approximately 55% higher effectiveness and a 63% reduction in hospitalization rates.
Long-lasting protection: Immunity lasts up to 12 months, whereas protection from injectable vaccines may decline after 4–6 months.
Reduced community transmission: Children and adolescents are major drivers of influenza spread. Vaccinating them helps protect households, schools, and the broader community.
Enhanced immune response: Because LAIV mimics natural infection, it induces both mucosal immunity (IgA) in the nasal passages and systemic immunity (T-cell responses) that can persist for at least one year.

Dosage and Schedule

Age Group	Dosage	Schedule

Children 2–8 years	1 or 2 doses* (0.2 mL total)**	If 2 doses are needed, they should be given at least 1 month apart.
Ages 9–49 years	1 dose (0.2 mL total)**	Single dose per season.

* The number of doses depends on prior vaccination history, based on national immunization guidelines.
** Each dose is 0.1 mL sprayed into each nostril.

Possible Side Effects

Most side effects are mild and temporary, resolving on their own. These may include:

Runny nose or nasal congestion
Low-grade fever

Some individuals may experience a slight cooling sensation during administration due to the fine mist droplets.

Current Recommendations

The Pediatric Infectious Disease Society of Thailand (PIDST) and the Infectious Disease Association of Thailand (IDAT) recommend annual influenza vaccination for everyone.

For individuals aged 2–49 years, the nasal spray flu vaccine (LAIV) is an effective and convenient option.
For children aged 6 months and older, inactivated injectable vaccines are also available and recommended.

Safety Considerations
LAIV is produced using a cold-adapted, temperature-sensitive strain of the influenza virus.
This means it can only replicate in the cooler temperatures of the nasal cavity and upper airways, and cannot multiply in warmer areas of the body such as the lungs.
As a result, the vaccine cannot cause influenza illness and is considered safe for eligible individuals.

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Nasal Spray Influenza Vaccine: Protection Without Injections