About influenza (flu)

Influenza also called the flu, is a serious and contagious respiratory illness that is caused by the influenza virus. Symptoms can range from mild to severe, sometimes leading to pneumonia, bronchitis, ear infections, and even death.

High risk group of seasonal influenza

Every year many people get sick with the flu. Some groups are at higher risk than others, including the elderly, young children, and people with certain health conditions.

Time get vaccinated

September and October are good times to get vaccinated. However, as long as flu viruses are circulating, vaccination should continue, even in January or later.

Vaccine types

There are three types of influenza vaccines:

(a)       Inactivated Influenza Vaccine (Flu shot);

(b)       Recombinant influenza vaccine (Flu shot); and      

(c)       Live-attenuated Influenza Vaccine (Nasal spray)

The inactivated influenza vaccine is formulated with the viruses that have been inactivated during the manufacturing process, the recombinant influenza vaccine contains haemagglutinin (a surface protein of influenza virus) that is produced by recombinant technology, and does not require egg or influenza virus in the production process, while the nasal spray contains viruses that are attenuated or weakened right at the beginning of the manufacturing.

The inactivated viruses are validated by the medical science that they only trigger restricted growth in the body and can hardly replicate themselves to manifest into a real illness. As opposed to the flu shot, the nasal spray simulates natural infection through the nose and may be able to induce stronger and long-lasting immune protection.

For both flu shots and nasal sprays, the effectiveness will depend on whether the virus strains in the vaccine, based on the WHO recommendation, are compatible with the virus strains circulating in the community.

Pros and cons of nasal spray

Pros:

• The only non-invasive alternative to the flu shot without a needle
• No pain from the injection
• Suitable for people who are afraid of needles

Cons:

• More restrictions on who can get
• A little more expensive than a flu shot
• Since it is given as a nose spray, some experts think it may not be as effective if your child's nose is very congested, such as if he has allergies or a cold.

Side effects of nasal spray

The viruses in the nasal spray flu vaccine are weakened and do not cause severe symptoms often associated with flu illness. In children, side effects from the nasal spray may include:

• Runny nose
• Wheezing
• Headache
• Vomiting
• Muscle aches
• Fever (low grade)
• Sore throat (in older children)

In adults, side effects from the nasal spray vaccine may include:

• Runny nose
• Headache
• Cough

These problems usually are mild and short-lived.

Contraindications for nasal spray

Some people should not get the nasal spray flu vaccine:

• Children younger than 2 years
• Adults 50 years and older
• People with a history of a severe allergic reaction to any ingredient of the vaccine or a previous dose of any influenza vaccine
• Children 2 years through 17 years old who are receiving aspirin- or salicylate-containing medications.
• Children 2 years through 4 years old who have asthma or who have had a history of wheezing in the past 12 months
• People with weakened immune systems
• People who care for severely immunocompromised persons who require a protected environment
• People without a spleen, or with a non-functioning spleen
• Pregnant women
• People with an active leak between the cerebrospinal fluid and the mouth, nose, ear, or another within the skull
• People with cochlear implants
• People who have taken flu antiviral drugs recently

Precautions on the use of nasal spray

The following conditions are precautions to the use of the nasal spray flu vaccine:

• Asthma in people aged 5 years and older.
• Other underlying medical conditions that can put people at higher risk of serious flu complications.
• Moderate or severe acute illness with or without fever.
• Guillain-Barré Syndrome within 6 weeks following a previous dose of flu vaccine.

Effectiveness of the nasal spray vaccine

The American Academy of Pediatrics did not recommend the nasal spray during the 2016-17 and 2017-18 flu seasons because it didn't work as well against the A/H1N1 viral strain, but with changes in the formulation of the spray vaccine, the CDC is recommending any licensed, age-appropriate flu vaccine with no preference for any one vaccine over another in 2023-2024 flu season.

Is it possible to have the COVID-19 vaccine together with the seasonal influenza vaccine?

Last year we mentioned that there are limited data on the simultaneous administration of covid-19 vaccines with other vaccines.  At the end of 2021, WHO announced that on an individual level, it would reduce the number of health care visits needed and provide timely protection against both diseases; these individual benefits may encourage greater uptake of the two vaccines. 

Further, Hong Kong Special administrative region’s CHP also stated that

"COVID-19 vaccines can be co-administered with, or at any time before or after, seasonal influenza vaccine (including inactivated influenza vaccine, live attenuated influenza vaccines and recombinant influenza vaccine) under informed consent. If clients/parents of children wish to space out the COVID-19 vaccine with SIV, an interval of 14 days is sufficient."

So, in other words, if you wish and have well informed, you can choose to have coadministered both the Covid vaccine and flu jab at the same visit to the clinic.

Is it possible to have flu and COVID-19 at the same time?

Yes. It is possible to have flu, as well as other respiratory illnesses, and COVID-19 at the same time. Some of the symptoms of flu and COVID-19 are similar, making it hard to tell the difference between them based on symptoms alone.

Source: CDC https://www.cdc.gov/flu/symptoms/symptoms.htm