Seroprevalence rate after one dose of varicella vaccine in infants.
BACKGROUND
Live, attenuated varicella vaccine has been used since 1988 in Korea. However, varicella is still prevalent among both vaccinated and unvaccinated individuals, despite a relatively high level of immunization rate up to 80%. A recent report has demonstrated approximately 20% of primary vaccine failure rate after one dose of varicella vaccine using the fluorescent antibody to membrane antigen (FAMA) assay.


METHODS
The seroprevalence rate was determined using the FAMA and ELISA assays in 67 Korean infants following one dose of varicella vaccine. Positive fluorescence at a serum dilution of 1:4 or greater was considered as seropositive.


RESULTS
The median age at vaccination was 12 months and the post-immunization sera were obtained on average 6.3 months (range 6 weeks-12 months) after vaccination. Among the 67 vaccinated infants, 56 (83.6%) were seropositive by FAMA assay while 30 (44.8%) were seropositive by ELISA. The geometric mean titers (GMTs) of the seropositive vaccinated infants (n = 56) were significantly lower than the GMTs of 9 individuals with a history of varicella (1:17.0 vs. 1:74.7, P = 0.001). Although there were no significant differences in seropositive rates according to intervals, there was a decreasing trend in the GMTs over time among the 56 seropositive recipients (r(2) = 0.154, P < 0.001).


CONCLUSIONS
These data can be useful for optimizing the immunization strategy against varicella and should be confirmed by a prospective study including a large number of immunized infants.
Kim
So Hee
SH
Department of Pediatrics, Seoul National University College of Medicine, Seoul, Republic of Korea.
Lee
Hoan Jong
HJ
Park
Su Eun
SE
Oh
Sung Hee
SH
Lee
Seong Yeon
SY
Choi
Eun Hwa
EH
D000328:Adult; D002644:Chickenpox / Q000453:epidemiology* / Q000517:prevention & control*; D019433:Chickenpox Vaccine / Q000008:administration & dosage* / Q000276:immunology*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007223:Infant; D008297:Male; D056910:Republic of Korea / Q000453:epidemiology; D016036:Seroepidemiologic Studies
D019433:Chickenpox Vaccine