Dr. Doctor,
I recently had a baby and was handed a vaccines schedule. I was astonished by the number of vaccines my child has to receive by the age of five. I have many questions. How do vaccines work? Are all vaccines 100 per cent effective? Can babies’ immune systems handle so many vaccines? Why can’t all the vaccines be combined into one injection and given once? Why do we have so many vaccines? So if vaccines are effective, why do some require boosters? Can my baby get a disease from the vaccine that’s supposed to prevent it? Mary
Dear Mary,
I hope our discussion last week put your questions to rest on how vaccines work. Today, I will attempt to help you understand how effective and safe they are.
Vaccines are designed to generate an immune response that will protect the vaccinated individual during future exposures to the disease.
While we all have similar immune system, there are some differences, which in some cases; a person’s immune system will not generate an adequate response. As a result, he or she will not be effectively protected after immunization. Aware of these subtle differences, vaccines have been tested to provide as high effectiveness as possible.
In Kenya, currently the expanded programme on immunizations recommends vaccine against 10 different disease causing agents for a child under one year - from birth to nine months of age. Since some are given as drops (polio and rotavirus diarrhoea vaccine) and others as injections (BCG/Pneumococcal), it is not possible to give them as one combination.
Besides, these pathogens have different strains, which may need forms of the same vaccine given on different occasions, to achieve total cover of all pathogen strains. A good example is polio drops, given at birth, at six, ten and 14 weeks of age.
Research shows that infants’ immune systems can handle receiving many vaccines at once—in fact much more than the number currently recommended. Countries like US and Europe have recommended and are giving many more vaccines than Kenya, up to 14 in the first year of life.
The immunization schedule is based on infants’ ability to generate immune responses, as well as when they are at risk of certain illnesses.
For example, the immunity passed from mother to child at birth is only temporary, and typically does not include immunity against polio, hepatitis B, Haemophilus Influenzae Type b, and other diseases that can be prevented by vaccination. The measles immunity however lingers on up to six to nine months.
If a vaccine has been made with killed versions of pathogens—or with only a part of the pathogen—it cannot cause illness. When your son receives this vaccine, it is impossible for him to become ill with the disease.
Live, attenuated (or weakened) vaccines are theoretically capable of causing illness: because they can still multiply (though not well), and may undergo mutation, which can result in a deadly form of the pathogen. However, these vaccines are designed with this in mind, and attenuated to minimize this possibility.