Background:
@EN Japanese encephalitis (JE), a mosquito-bemo flaviviral disease of humans and animals, is a major public health problem in Asian country, where an estimated 50,000 cases occur annually. Since several decade ago inactivated JE vaccine has been
used in
Korea with the national expanded immunization program which consists of three primary doses; two consecutive vaccination with one month interval and one booster vaccination at 12 months after second injection, and annual revaccination thereafter.
However this annual revaccination schedule has not yet been justified immunologically, practically and economically. We retrospectively reviewed the immunization history and concurrently examined humoral immune response to JE virus to determina
whether
the current annual revaccination after primary vaccination is neccesary in Korean children
@ES Methods:
@EN Methods: We tested rera from children who had the history of JE vaccination in 1993 or 1994, for antibodies against JE virus by hemagglutination inhibition test and plaque reduction neutralization test. Seropositivity rates of
hemagglutination(HI)
antibody and geometric mean titers(GMT) of netrualizing antibody(NA) were compared according to the type of immunization schedule(primary or booster).
@ES Results:
@EN The total enrolled subjects were 333; 1994 vaccinees were 119(35.7%) and 1993 vaccinees, 131(39.3%)
1) Among 131 subjects who received the last vaccination in 1993, the seropositive rates of HI antibody against JE virus of primary vaccination group(PVG) and booster vaccination group(BVG) were 46.7% and 72.3%. respectively (p value<0.01) and
GMTs
of NA
of two group were 15.5 and 18.8, respectively (p>0.7)
2) Among 119 subjects who received the last vaccination in 1994, the seropositive rates of HI antibody of PVG and BVG were 41.7% and 68.4%, respectively(pvalue<0.01)and GMTs of NA of two groups were 15.2 and 17.7, respectively(p>0.3)
3) The seropositive rates of HI antibody of 54 subjects who had only primary vaccination in 1993 or 1994 were 46.7% and 41.7%, respectively (p value>0.9) and GMTs, 15.5 and 15.7, respectively (p value>0.6).
4) The seropositive rato of HI antibody of 194 subjects who had booster vaccination in 1993 or 1994 were 72.3% and 68.4%, respectively (p >0.5) and GMTs, 18.8 and 17.7, respectively (p>0.8).
5) The seropositive rate of HI antibody of 56 subjects who had only primary vaccination and 203 subjects who had booster vaccination were 48.6% and 66.8%, respectively (p<0.01)
@ES Conclusion:
@EN This data showed that we need three doses of consecutive vaccination, as two dose primary vaccination with one month interval and one booster dose after primary vaccination at 12 month later, for acqusition of primary immunity against JEV and
we may
be able to change the annual revaccination schedule to two years intervals, after acqusition of primary immunity through three consecutive vaccination.
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