[Studies on immunization strategy against hepatitis A in a highly prevalent area].Zhonghua Yu Fang Yi Xue Za Zhi. 1998 Sep; 32(5):295-6.ZY
To explore a strategy for immunization against hepatitis A (HA) in highly prevalent areas.
Maternal antibodies against hepatitis A virus (anti-HAV) were detected for newly born infants and infection rate of HAV was monitored for children at various stages of epidemic of HA.
Proportions of positive maternal anti-HAV in newly born infants decreased from 97.4% to 5.0% during their first 13 months of life in a logistic curve pattern. HAV infection increased with age after one and a half years old during non-epidemic period, and kept in less than 10% before two years old. The age of the increase in HAV infection shifted to an earlier dates and the rate of infection speeded up more for children during an epidemic period. The "window" phase converting maternal anti-HAV to natural infection for infants in the highly prevalent areas was in 12 to 24 months after birth, because the age starting to increase HA infection lagged behind that of infection.
Based on the prevalence of HA and economic situation, the appropriate time for children's HAV immunization is 12 to 24 months of age.