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Key Facts about Influenza (Flu) Vaccine

There are two types of vaccines:

  • The “flu shot” – an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. The flu shot is approved for use in people older than 6 months, including healthy people and people with chronic medical conditions. Palomar Health will only give this vaccine.
  • The nasal-spray flu vaccine – a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for “Live Attenuated Influenza Vaccine”). LAIV is approved for use in healthy people 5 years to 49 years of age who are not pregnant.

Each vaccine contains three influenza viruses – one A (H3N2) virus, one A (H1N1) virus, and one B virus. The viruses in the vaccine change each year based on international surveillance and scientists’ estimations about which types and strains of viruses will circulate in a given year 2 weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body.

Influenza is the 7th leading cause of death in the U.S.

When to get vaccinated?
October or November is the best time to get vaccinated, but you canstill get vaccinated in December and later. Flu season can begin as early as October and last as late as May.

Does the flu vaccinationwork right away?
No.It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection.In the meantime, you are still at risk for getting the flu.That’s why it’s better to get vaccinated early in the fall, before the flu season really gets under way.

Can I get the flu even though I got a flu vaccine this year?
Yes.The ability of flu vaccine to protect a person depends on two things:1) the age and health status of the person getting the vaccine, and 2) the similarity or “match” between the virus strains in the vaccine and those in circulation.

Why do I need to get vaccinated against the flu every year?
Flu viruses change from year to year, which means two things.First, you can get the flu more than once during your lifetime.The immunity (natural protection that develops against a disease after a person has had that disease) that is built up from having the flu caused by one virus strain doesn’t always provide protection when a new strain is circulating.Second, a vaccine made against flu viruses circulating last year may not protect against newer viruses.That is why the influenza vaccine is updated to include current viruses every year.

Common flu symptoms

Influenza usually starts suddenly and may include the following symptoms:

  • Fever (usually high)
  • Headache
  • Tiredness (can be extreme)
  • Cough
  • Sore Throat
  • Runny or stuffy nose
  • Body Aches
  • Diarrhea and vomiting (more common among children than adults)

Having these symptoms does not always mean that you have the flu.Many different illnesses, including the common cold, can have similar symptoms.

Effective July 1, 2006, it will be against California law to administer doses of a few vaccine formulations to pregnant women or children younger than three years old because of their level of mercury containing preservative, thimerosal [Health and Safety (H&S) Code Section 124172, Chapter 837, Statutes of 2004 (AB 2943, Pavley)].

Effective July 1, 2006, pregnant women or children younger than three years old may only receive vaccine doses that contain trace levels or no mercury. This law does not apply to persons who are three years of age and older and who are not pregnant. Thimerosal is a mercury containing compound which has been used as a preservative in vaccines since the 1930’s.Thimerosal is used in multi-dose vials ofinactivated influenza to reduce the likelihood of bacterial contamination.Many single dose syringes and vials today are thimerosal free or contain only trace amounts.There is no evidence that indicates thimerosal in vaccines can lead to serious adverse events in people who receive it.

Palomar Health does not use flu serum containing any amounts of thimerosal.

Additional information about this new law is available at: