The flu, or influenza, is a contagious respiratory illness that affects the nose, throat, and sometimes even the lungs. It spreads through tiny droplets released when an infected person coughs, sneezes, or talks. While flu infections are usually harmless for young and healthy individuals, those with pre-existing medical conditions and older adults should take extra precautions against the virus.
Although the flu is not 100% preventable, vaccines offer the best defence against the virus. If you've received the flu shot once, you may need to get it again periodically to maintain protection. In this article, we will find out how often you should update your flu vaccines and the duration of effectiveness for the flu shot.
Also Read: Is Now A Good Time To Get Your Flu Shot? Who Should Consider It
How Do Flu Vaccines Work?![]()
Did you know that as many as 6.5 lakh people die of the flu annually? According to the World Health Organization (WHO), this only includes respiratory deaths, which is why the numbers could be even higher.
The flu vaccine is one strong shield against the virus that causes the flu. It works by causing your body to produce antibodies to protect you from the flu viruses included in the vaccine. While some people have the misconception that flu vaccines can make people sick, that is not the case because the injected flu vaccine contains an inactivated virus that cannot give you influenza. If you feel achy or slightly feverish, it is a normal reaction of the immune system to the vaccine and generally lasts only a day or two, explains the WHO.
How Long Does Immunity From Flu Shot Typically Last?![]()
In an interaction with the OnlyMyHealth team, Dr Manoj A. G., Consultant Physician, Consults on Practo, says, “The immunity from the flu shot typically lasts about 6 months. This duration varies depending on factors like the person’s age, health status, and the match between the vaccine strain and circulating viruses. Immunity tends to wane by the end of the flu season, especially in older adults.”
He further added, “The flu vaccine’s effectiveness can diminish over time as the immune response weakens after several months. It’s updated annually to match the circulating flu strains, which can change each year due to antigenic drift. Annual vaccination is recommended.
It is also important to understand that the flu vaccine is reformulated annually based on global surveillance data that predicts the most likely circulating strains. It typically includes protection against four strains (two influenza A and two influenza B), providing broad protection against multiple variants, though exact efficacy depends on the match between vaccine and virus.
Also Read: What Happens When the Immune System Invades Your Own Tissue ? Know About Lupus
Do Some People Require Frequent Flu Vaccination?![]()
Populations like immunocompromised individuals, older adults (65+), and those with chronic health conditions may not have a strong or long-lasting immune response. While one annual shot is the standard, these groups should be vigilant during flu season and seek medical advice on additional preventive measures.
Side Effects Of Flu Vaccines To Note
According to Dr Manoj, flu vaccines can cause side effects in some people.
Common side effects are mild and include soreness at the injection site, low-grade fever, or fatigue, lasting 1-2 days.
However, it is crucial to remember that these are minimal compared to the risk of flu complications like pneumonia, hospitalisation, or death, particularly in high-risk populations. The vaccine significantly reduces the severity of illness even if infection occurs.