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Original ArticleOpen Access
Antibody Response After Measles Immunization
Ariyasriwatana C 
,
Kalayanarooj S ,
Pattamadilok S
,
Kalayanarooj S ,
Pattamadilok S Rationale
: Measles is still an important public health problem in Thailand despite measles
vaccination being practiced since 1984. Vaccine failure is one of the suspected reasons for the high
incide~ce
of measles.
Objective
: To study the seroconversion rate of 9-month-old infants and to study the anti-
body level in 18 month-old and 4 year-old children who had measles vaccination at 9 months of age.
I
Material and Method
: Enrolled infants and children who attended the child health clinic for
routine immunization at the Queen Sirikit National Institute of Child Health from March 1, 1994 to
May 31, 1995. They were divided into 3 groups. Group A, 9 month-old infants who came for measles
vaccinati~n.
Blood samples were drawn twice from these infants, before measles vaccination and 3
months later for measles antibody level. Group B and C were 18 month-old and 4-year-old children who
came for their first and second DTP (Diphtheria, Tetanus, Pertussis vaccine) booster. One blood sample
for measles antibody was drawn from the latter group of children. Measles antibody was determined
by micro-neutralization technic at the National Institute of Health (NIH). The geometric mean antibody
titer before and after measles vaccination was compared by using the paired !-test.
Results:
There were 30, 31 and 34 infants/children in group A, Band C respectively. No
significant measles antibody (NT antibody was less than 1 : 4) was detected in 93.5 per cent of 9-
month-old infants. The seroconversion rate at 3 months after vaccination in group A children was 68.75
per cent while in group B, 9 months after vaccination it was 53.3 per cent. Ninety seven per cent of
children in group C had NT antibody above 1 : 4. The geometric mean titer (GMT) of measles antibody
in 9-month (before vaccination), 12-month, 18-month infants and 4 year old children was 1 : 2.5, 1 : 14.8,
1 : 8.2 and 1 : 73.8, respectively (p
<
0.05).
Conclusion
: Almost 70 per cent of vaccineec: at 9 months of age had seroconversion to
measles vaccine with GMT of 1 : 14.8 while fifty three per cent of 18 month old children had an average
GMT of 1 : 8.2. The GMT of the two groups was significantly different (p
<
0.05). At 4 years of age
almost all the children had NT antibody to measles with a GMT of
1
:
73.8 (p
<
0.05)
Vaccine failure is likely to be one factor responsible for the high incidence of measles after
the introduction of measles vaccine into the Expanded Program of Immunization (EPI).
8702
: Measles is still an important public health problem in Thailand despite measles
vaccination being practiced since 1984. Vaccine failure is one of the suspected reasons for the high
incide~ce
of measles.
Objective
: To study the seroconversion rate of 9-month-old infants and to study the anti-
body level in 18 month-old and 4 year-old children who had measles vaccination at 9 months of age.
I
Material and Method
: Enrolled infants and children who attended the child health clinic for
routine immunization at the Queen Sirikit National Institute of Child Health from March 1, 1994 to
May 31, 1995. They were divided into 3 groups. Group A, 9 month-old infants who came for measles
vaccinati~n.
Blood samples were drawn twice from these infants, before measles vaccination and 3
months later for measles antibody level. Group B and C were 18 month-old and 4-year-old children who
came for their first and second DTP (Diphtheria, Tetanus, Pertussis vaccine) booster. One blood sample
for measles antibody was drawn from the latter group of children. Measles antibody was determined
by micro-neutralization technic at the National Institute of Health (NIH). The geometric mean antibody
titer before and after measles vaccination was compared by using the paired !-test.
Results:
There were 30, 31 and 34 infants/children in group A, Band C respectively. No
significant measles antibody (NT antibody was less than 1 : 4) was detected in 93.5 per cent of 9-
month-old infants. The seroconversion rate at 3 months after vaccination in group A children was 68.75
per cent while in group B, 9 months after vaccination it was 53.3 per cent. Ninety seven per cent of
children in group C had NT antibody above 1 : 4. The geometric mean titer (GMT) of measles antibody
in 9-month (before vaccination), 12-month, 18-month infants and 4 year old children was 1 : 2.5, 1 : 14.8,
1 : 8.2 and 1 : 73.8, respectively (p
<
0.05).
Conclusion
: Almost 70 per cent of vaccineec: at 9 months of age had seroconversion to
measles vaccine with GMT of 1 : 14.8 while fifty three per cent of 18 month old children had an average
GMT of 1 : 8.2. The GMT of the two groups was significantly different (p
<
0.05). At 4 years of age
almost all the children had NT antibody to measles with a GMT of
1
:
73.8 (p
<
0.05)
Vaccine failure is likely to be one factor responsible for the high incidence of measles after
the introduction of measles vaccine into the Expanded Program of Immunization (EPI).
8702
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