My Child & I: Vaccination – Part III

In Part I of this series, we discussed the basic workings of vaccines, while in Part II we described the differences between the different types of vaccine available and how it can affect your child’s vaccination. Here we shall learn a bit more about vaccination series and boosters. Dont forget to read Part IV for more information.

Part III: Vaccine series & boosters

What is a vaccine series?

In Part I of this series, we had mentioned how vaccines try to lock the immune response into the long-term memory cells of the immune system. Often this requires more than a single innoculation. The number of sequential doses of the same vaccine needed to succefully produce a longterm protective effect is known as the primary series of a vaccine. This is the minimum number of doses needed to be given to a patient with no history of previous such vaccination(s) in order to provide a longterm protective effect for the patient. The number of doses in the primary series for the same illness(s) may vary from person to person depending on

  1. the specific vaccine being used

  2. the age of the patient

  3. the presence of special conditions ( e.g. patients being born to Hepatitis B carrier mums are generally recommended an additional dose of Hepatitis B vaccine)

Why does my child  have to wait so long between shots?

The timing of a sequential shots of a primary series are very crucial. In children especially, there is a minimum age which the child has to be in order to be started on any particular vaccine. This is because the immune system gradually matures with the child and a vaccine given at too early an age may not be able to produce the desired response, or worse yet may overwhelm the immune system of the child and cause serious harm.

Once the initial vaccine has been administered, the series should be carried out to completion. Generally, the primary series will consist of 2 or more doses if the same vaccine given a specified time apart from one another. The interval between each dose allows the immune system to gradually adapt and remember the particular trigger so that as future doses are given, the details of the offending agent are locked into the longterm memory cells of the immune system.

What are boosters?

As time goes on, the memory cells pertaining to immunity against a particular infection(s) may begin to dwindle and fade away from lack of use. This is where booster doses come in. Booster vaccines are given to spur the already present memory cells into activity, thereby refreshing their supply and prolonging the duration of effect. Not all vaccines require a booster. For example, it is generally assumed that the MMR primary series confers lifelong protection against Measles, Mumps and Rubella. In contrast, it is generally accepted that tetanus (a component of the primary DPT series) needs routine boosters, and often patients with cuts and scrapes prone to tetanus infections will be given an anti-tetanus booster if the interval from the last dose has been too long.

It is generally accepted that if one should complete a primary series of vaccines, he/she need only get a booster at the recommended intervals or as circumstances dictate. In a rare few cases, there may be a need to redo the primary series of the vaccine (e.g. in cases where there have been conclusive tests to show that the patient has not mounted an immune response at all). These circumstances however are very much the exception rather than the norm.

Now that we know more about the different types of vaccines and how they work, let’s try to figure out when and what to get your child vaccinated against in the next and final part of this series.


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  1. My Child & I: Vaccination – Part IV | Children's Health - […] Parts I, II and III, we’ve learnt about vaccines, how they work and what vaccine series and boosters are.…
  2. My Child & I: Vaccination – Part I | Children's Health - […] vaccines are important for the well being of you and your loved ones. Don’t miss Parts II, III &…
  3. My Child & I: Vaccination – Part II | Children's Health - […] the different types of vaccines available and how this affects your child. Dont forget to read Parts III &…