Some vaccines need to be administered multiple times, while some only require one shot, in order to confer adequate protection. — Positive Parenting
Vaccines confer protection against the infectious disease they cover.
Since their introduction, vaccines have helped save many lives by protecting us against potentially life-threatening diseases.
A peek into a child’s vaccination booklet will reveal the need for multiple doses of vaccines such as the DTaP (diphtheria, tetanus and pertussis), IPV (inactivated polio vaccine), HepB (hepatitis B) and HiB (Haemophilus influenzae type B), while only one dose of BCG (Bacillus Calmette-Guérin, for tuberculosis) is required.
On the other hand, one needs to take the influenza vaccine annually.
Why do some vaccines require multiple dosing, some require annual shots, while some are only given once?
To better understand this, let’s have a look at how vaccines work.
Vaccines comprise bits and pieces of bacteria or viruses, which will trigger the recipient’s immune system to produce antibodies when injected or ingested.
However, in young babies, one dose may not produce a high enough level of antibodies, or the antibodies may not last for long.
In order to generate a sufficiently high level of antibodies and for these antibodies to last longer, multiple doses are given.
These doses are timed such that each dose pushes the antibodies to a higher level.
Examples of vaccines that require multiple dosing in infancy, as well as booster doses, are:
- DTaP, IPV, HepB and HiB (hexavalent vaccine) – given at two, three and five months of age as the primary series, and at 18 months as a booster dose.
- Measles, mumps and rubella (MMR) – given at nine and 12 months of age.
- Pneumococcal conjugate vaccine (PCV) – given at four and six months of age as the primary series, and at 15 months as a booster dose.
In the case of influenza vaccines, they need to be taken annually due to viral mutations.
The influenza virus comprises several strains, of which two affect humans.
These are influenza A and B.
Within these strains are several subtypes that mutate regularly.
Due to these mutations, the main subtypes that cause the most infections among humans change over time.
And a vaccine for a particular subtype, e.g. H1N1, will not confer protection against other subtypes.
In addition, the body’s antibody levels triggered by the influenza vaccine start to drop about a year after receiving the injection, and are no longer sufficient to confer protection.
Therefore, in order to be protected, a person needs to get the latest vaccine.
The current influenza vaccines in the market are what are called quadrivalent vaccines.
They comprise two subtypes of influenza A and two subtypes of influenza B, which are changed from year to year.
The subtypes in the vaccine are determined by experts based on their observations and predictions of which four viral subtypes will be the most dominant for the coming year.
The influenza vaccine can be given as early as six months old.
Ideally, everyone should get annual influenza shots; however, some groups are at higher risk of getting severe influenza infection than others.
They are:
- Pregnant women
- Children under the age of five years
- Adults over 65 years of age
- Healthcare workers
- Individuals with chronic medical conditions, e.g. diabetes, asthma, chronic lung disease and chronic obstructive pulmonary disease (COPD)
- Individuals who live with young babies and other vulnerable individuals who may not be able to take the vaccine themselves.
Dr Yong Junina Fadzil is a consultant paediatrician and paediatric cardiologist. This article is courtesy of the Malaysian Paediatric Association’s Positive Parenting programme in collaboration with expert partners. For further information, please email starhealth@thestar.com.my. The information provided is for educational and communication purposes only, and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
