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Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 2 minutes read

A vaccine (also known as vaccination, immunization, or jab) is when your body is given a modified version of a virus or bacteria so that your immune system can develop immunity against it without getting the harmful illness associated with it. This is usually in the form of a small injection and is why it is also known as a "jab" and tends to be given into the muscle in your upper arm.

Vaccines have been key in preventing serious and potentially fatal infectious diseases. There are also seasonal vaccines, such as the flu vaccine and travel vaccines, that you will only require if you are traveling to certain places abroad where some diseases are more prevalent than in the US. There are also specific vaccines, such as hepatitis, depending on your risks of exposure to blood-borne viruses.

The bacteria or viruses are made safe for a vaccine by either weakening, changing, or killing them so that they cannot cause harm. If a vaccine uses a weakened version of the pathogen (virus or bacteria), then it should be considered whether it is safe to give to people with a lowered immune system.

All approved and licensed vaccines have gone through clinical trials, meaning that they have been thoroughly tested and are safe for use. The side effects of vaccines are usually mild and short-lived; however, in a very small number of people, a severe allergic reaction can occur, known as anaphylaxis. It is not common, but it is life-threatening. It can develop quickly, causing the swelling of airways and difficulty breathing along with other symptoms such as feeling faint or dizzy, feeling sick, and collapsing. Any signs of anaphylaxis should be responded to by calling 911 immediately.

Routine vaccines

There are many vaccinations that are offered as a matter of routine here in the US. They are recommended at different ages and on a standard protocol throughout childhood. This is known as the childhood immunization program and includes vaccinations such as immunity to meningococcal bacteria, measles, mumps, rubella, rotavirus, and more.

Healthwords pharmacists' top tips

If you are traveling abroad, you can seek advice from your pharmacist about precautions or what vaccinations you may need. You can also book a travel appointment with your doctor or at private clinics. It is best to do this at least 2 months before you plan to travel.

When should I see my doctor?

If you or your children have missed any routine vaccinations for any reason, then it is important to book a routine doctor's appointment. If you have had an allergic reaction to a vaccine in the past or have a severe egg allergy, it is best to check with your doctor prior to having any vaccines as to whether it is safe for you to have it (some vaccines contain egg proteins in them).

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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