My 3-year old daughter is presently with measles. It started as high grade remittent fever for three days followed by maculopapular rash that started from the head downwards, very typical of the disease. This occurrence frustrated us, especially my wife who's a pediatrician, because my daughter received 2 doses of measles vaccine already, following strictly the recommended scheduled. It made us think and somewhat doubt the effectivity of the vaccines. But, as doctors, we knew this could happen. We are familiar with 'vaccine failures' and we just felt sorry that our daughter is now included in the small unfortunate population of victims.
The rate of vaccine failure is reported to be around 9.5% for measles virus. Most cases of measles in vaccinated persons occur in the subset of individuals who did not undergo serological conversion after vaccination. This is known as primary vaccine failure. The frequency of primary vaccine failure is variable and has been shown to be a function of age at the time of vaccination, the number of doses, the immunogenicity of the strain of the virus used to manufacture the vaccine, and the geographic region. Secondary vaccine failure is defined as the occurrence of measles in persons in whom postvaccination serologic conversion has been documented. This type of failure are more common than was previously thought, particularly among individuals vaccinated in early life. Waning immunity even among individuals vaccinated after 15 months of age, without the boosting effect of natural infections is considered a relevant possibility.
The rate of vaccine failure is reported to be around 9.5% for measles virus. Most cases of measles in vaccinated persons occur in the subset of individuals who did not undergo serological conversion after vaccination. This is known as primary vaccine failure. The frequency of primary vaccine failure is variable and has been shown to be a function of age at the time of vaccination, the number of doses, the immunogenicity of the strain of the virus used to manufacture the vaccine, and the geographic region. Secondary vaccine failure is defined as the occurrence of measles in persons in whom postvaccination serologic conversion has been documented. This type of failure are more common than was previously thought, particularly among individuals vaccinated in early life. Waning immunity even among individuals vaccinated after 15 months of age, without the boosting effect of natural infections is considered a relevant possibility.
Analysis of the number of vaccine doses and the type of vaccine failure showed that the group of measles patients who had received two vaccine doses after 1 year of age had a rate of primary vaccine failure significantly lower than that of the group of patients who had received a single vaccine dose before 1 year of age or of the group of patients who had received only one dose after 1 year of age.
This is the reason why it has been suggested that protection against measles necessitates vaccine administration at the appropriate age. Vaccine failure can result when passively acquired maternal antibodies neutralize the vaccine virus before the patient develops an immune response. The vaccine must also be administered at an age old enough when the chances for the maternal antibody neutralization are low but young enough to avoid the risks of infection.
REFERENCES:
Pannuti et al. Clin Diagn Lab Immunol. 2004 January; 11(1): 119–122.
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