Overview and Definition

Vaccines are one of the most important and most effective ways in preventing certain diseases and maintaining overall health. Vaccines, also known as immunizations, take full advantage of the body’s unique feature of learning and adapting as far as fighting disease-causing germs is concerned. They help create immunity to protect you from an infection without causing any harmful side effects.

How Vaccines Work

Vaccines are primarily aimed at protecting you by getting your immune system ready to identify and fight serious diseases that can range from minor to life threatening. These contain antigens that have previously been disabled and, therefore, can be safely introduced to the body without causing the ill effects of the related disease.

As the antigens are still recognized as foreign bodies, their presence in the bloodstream triggers the immune system to release protective antibodies to counter them. Also called B cells, these special cells stay in the body permanently to identify and fight the disease caused by the virus or bacteria, should it invade your body again. This means that if you come in contact with the microbe in the future, your body can effectively eliminate it before it can cause any significant harm to your health. Essentially, vaccines can safely expose you to a bacteria or virus to protect you from the disease in the future.

Immunizations for certain diseases have to be strengthened which is why multiple scheduled rounds of the same vaccine are suggested for some conditions.

Benefits of Vaccines

With a vaccine against a particular disease, the immune system is effectively and permanently taught how to resist and fight it – a condition known as immunity. It is much more economical to prevent a disease rather than to treat it. Aside from inducing immunity, vaccines also offer benefits to others around you. Since your body is primed to stop the illness, you prevent your family, friends, neighbors and colleagues from contracting the disease as well. This is the why vaccines are central in public health campaigns.

Types of Vaccine

Vaccines are generally categorized into seven types and they are classified according to how they were designed to create the weakened microbe. Among the types of vaccines are:

  • Live, attenuated vaccines: consist of a version of the germ that has been weakened but still alive

  • Inactivated vaccines: contain microbes of the disease that have been killed by radiation, heat or chemicals

  • Sub-unit vaccines: do not contain the entire microbe, but only a sub-unit chosen to best stimulate the immune system

  • Toxoid vaccines: prepared using chemically-inactivated bacterial toxins

  • Conjugated vaccines: these are antigens linked to sugar molecules and are made especially for bacterial molecules coated with polysaccharides

  • DNA vaccines: these are made of the actual DNA makeup of the microbe

  • Recombinant vector vaccines: similar to DNA vaccines, these use attenuated bacteria or virus to introduce the microbial DNA into the body

Among common vaccines widely suggested at recommended schedules are immunizations for the following diseases and conditions:

  • Chickenpox
  • Diphtheria
  • Haemophilus
  • Influenza Type B
  • Hepatitis A
  • Hepatitis B
  • Human Papillomavirus (HPV, genital or venereal warts)
  • Influenza
  • Measles
  • Meningococcal Disease
  • Mumps
  • Pertussis (Whooping cough)
  • Pneumococcal Disease
  • Poliomyelitis
  • Rubella
  • Shingles
  • Tetanus

Who Needs Vaccines and When

Vaccines are necessary from birth through adulthood. Even seniors aged 65 and older can still enjoy their preventative benefits. Your family doctor will give you proper advice and schedule your immunizations. Talk to your health care provider for immunizations that you may have missed, and those recommended for your age, lifestyle and health status. Vaccines are designed to be safe and convenient, whether administered to an infant or adult.

Although vaccines are safe to be given at anytime without prior consultation, certain conditions may require medical advice before any immunization. Make sure to consult first if you:

  • Are possibly pregnant
  • Are breastfeeding
  • Have severe allergies
  • Have a history of chronic illness
  • Have had an allergic reaction to a previous vaccine
  • Have immune system problems
  • Recently received a transfusion
  • Have a history of seizures

If you think your child or even you are falling behind on your vaccine, there is no need to worry. Vaccines can be administered at any age, and it is easy to get back on track. Some states even have provisions for immunizations, so better check with your state health department. It is also best to keep your immunization records to show your doctors which ones you have had.

Side Effects of Vaccines

Vaccinations often cause side effects after administration but are usually minor and disappear within a day or two. Some common side effects include:

  • Itching and discomfort at the injection site
  • Pain, tenderness, redness or swelling at the injected area
  • Mild fever
  • Mild rash
  • Dizziness, nausea or fainting (usually in adolescents)
  • Feeling of fatigue and restlessness
  • Headache

You must be on the lookout for serious unusual conditions such as extreme weakness, high-grade fever and behavioral changes. If there are severe allergic reactions such as difficulty in breathing, wheezing, hives and unusually fast heartbeat, you should consult your doctor immediately. Although rare, these serious side effects are usually compiled into a database called the Vaccine Adverse Event Reporting System that is made available for public viewing and reference.

The Truth about Vaccines

There is a growing controversy about vaccines, with some claiming that they cause serious side effects. These include claims that they can cause autism. However, it should be noted that while these claims have no scientific backing to prove a causal relationship, vaccinations have long been proven to protect people from a host of harmful infectious diseases. Vaccines undergo many years of rigorous safety testing prior to approval by the FDA and administration to the public. Vaccines are also constantly monitored for safety. They have been used for decades and have proven to save millions of lives. They continue to be one of the cornerstones in maintaining public health.


  • Plotkin SA, Orenstein WA, Offit PA, eds. Vaccines. Philadelphia: Saunders; 2008.

  • National Health Service (2014). “How Vaccines Work.” Available: http://www.nhs.uk/conditions/vaccinations/pages/how-vaccines-work.aspx

  • U.S. Dept. of Health and Human Services, National Institute of Health (2008). NIH Publication No. 08-4219 “Understanding Vaccines – What They Are and How They Work.” Available: www.niaid.nih.gov/topics/vaccines/documents/undvacc.pdf

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