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To evaluate the population immunity to measles in Taiwan where the coverage rate of the measles vaccine was95% for more than a decade, anti-measles IgG was determined in 3552 Taiwanese volunteers in 2007. The overall seroprevalence was 74.7% (95% confidence interval [CI]: 73.3-76.1%). In subgroups aged 2-25 years, to whom at least 2 doses of measles-containing vaccine were given, there was a declining trend of seropositivity with age from 94.5% at 2 years to 50.6% at 21-25 years (p0.0001). Age (odds ratio [OR]: 1.0464, 95% CI: 1.043-1.085) and male gender (OR: 1.466, 95% CI: 1.131-1.901) were independent factors predicting seronegative sera in this population. Seroprevalence was uniformly95% in the older population (≥ 35 years) who had not been immunized against measles. The waning vaccine-induced immunity may have impact on the control of measles in the future, especially when the vaccinated population becomes older.

This study compared safety, tolerability, and immunogenicity of the Oka/Merck varicella vaccine and VARILRIX [Oka-RIT strain SmithKline Beecham Biologicals] in healthy children 12-24 months of age. Subjects were randomized in this double blind study to receive either a single dose of Oka/Merck varicella vaccine, (approximately 50,000 plaque forming units (PFU), Group A or approximately 16,000 PFU, Group B) or 1 dose of VARILRIX, (approximately 40,000 PFU/dose, Group C). Safety profiles in each treatment group were similar. The proportions of subjects achieving a 6-week postvaccination titer> or = 5 gpELISA units in Groups A, B or C were 97.1, 95.2 and 85.6%, respectively.

Long-term persistence of hepatitis A virus (HAV) serum antibody in vaccinated children has not been demonstrated in previous studies. To study the long-term immunogenicity to HAV vaccine, three doses of strain HM 175 HAV vaccine with 360 enzyme-linked immunosorbent assay units were administered to 107 children, aged from 1.0 to 6.8 years, at 0, 1, and 6 months. The administration of one vaccine dose induced seropositivity (anti-HAV titer > or = 20 mIU ml-1) in 95% of all vaccinees at month 1. All subjects remained seropositive until month 6. The titers of HAV antibody remained above 20 mIU ml-1 in all subjects followed up to 60 months. The geometric mean titer (GMT) reached its peak (3802 mIU ml-1) at month 7, i.e. 1 month after the booster dose, and then declined until the end of follow-up at month 60 (661 mIU ml-1). A trend of higher GMT in female subjects persisted up to month 60. The changes of the GMT over time were best described by the regression equation: log (GMT) = 3.26-0.08 x (age in years) (r = -0.95, P = 0.014). According to this equation, the geometric mean concentration would reach 20 mIU ml-1 at around 24.5 years after the beginning of vaccination. In conclusion, those who completed the recommended three-dose inactivated HAV vaccination series remained seroprotective for at least 5 years. Theoretically, such a vaccination program can provide a protective period of over 20 years in children. This paper may be the first to describe at least 5-year immunogenicity of inactivated HAV vaccination in healthy children.

A second generation acellular pertussis vaccine (component pertussis vaccine) containing purified pertussis toxin (PT) and filamentous hemagglutinin (FHA) was tested for its immunogenicity and safety in 2-month-old infants in comparison with first-generation acellular and whole-cell pertussis vaccines. At the ages of 2, 4, 6, and 18 months, respectively, 350 subjects were inoculated one dose of pertussis vaccine, which was combined with diphtheria and tetanus toxoids. Both acellular and component vaccines elicited significantly much fewer local and systemic reactions than whole-cell vaccine did. Besides, although not reaching statistical significance, the component vaccine was less reactogenic than the acellular vaccine. After each dose of the primary immunization, antibodies against PT and FHA were much higher in acellular and component pertussis vaccinees than in whole-cell vaccinees. However, at 18 months of age, just before the booster dose, both anti-PT and anti-FHA declined very close to, or even lower than, the prevaccination levels in all three groups and then responded rapidly to a booster dose to attain high levels. The booster responses were also significantly higher (P

This study was aimed to evaluate the efficacy and immunogenicity of combined hepatitis B vaccination with plasma-derived vaccine (PDV) and recombinant vaccine (RV). A total of 329 infants was recruited, including 224 high-risk infants born to hepatitis B e antigen-positive mothers and 105 low-risk infants born to hepatitis B e antigen-negative mothers. The high-risk infants received four doses of hepatitis B vaccine at 0, 1, 2 and 12 months of age with five different schedules. Group A1 and A2 infants were vaccinated with PDV as the first dose and RV (SB vaccine for group A1, MSD vaccine for group A2) as the remaining three doses. Group B1 and group B2 infants were vaccinated with PDV as the first two doses and RV (SB vaccine for group B1, MSD vaccine for group B2) as the remaining two doses. Group C infants received four doses of PDV. Low-risk infants were vaccinated with PDV at birth, and RV at 1 and 6 months of age (group D1, using SB vaccine; group D2, using MSD vaccine). At completion of vaccination schedules, 20 of 224 high-risk infants (9%) were positive for hepatitis B surface antigen. The overall protective efficacy was 90%. Hepatitis B surface antibody (anti-HBs)-positive rate ranged between 94 and 100% among the remaining infants. The protective efficacy and immunogenicity were similar among groups except that the mean level of anti-HBs in group C, D1 and D2 infants tended to be lower than that of the other four groups. To ensure an optimal immune response, four doses of vaccine are recommended in high-risk infants when two types of vaccine are to be used in combination.

Fifty-three children who failed to respond to four doses of plasma hepatitis B (HB) vaccine (anti-HBs titre10 IU l-1) were divided into two groups and received revaccination with either three doses of recombinant HB vaccine (10 micrograms/dose, by 0, 1, 6 month schedule; group A) or two additional doses of plasma HB vaccine (5 micrograms/dose, by 0, 1 month schedule; group B) respectively. Thirty-two vaccinees in group A had a response rate (with anti-HBs10 IU l-1) of 53.1% (17/32), 87.5% (28/32), and 100% (32/32) after first, second and third doses of the vaccine respectively. Twenty-one vaccinees in group B had a response rate of 61.9% (13/21) after two additional doses of plasma vaccine. High anti-HBs titres (1000 IU l-1) were noted in 50% of the vaccinees in group A after three doses of vaccine. Comparing anti-HBs response between group A and group B after two additional doses of HB vaccine, group A had a higher anti-HBs titre (geometric mean titre 104.7 IU l-1 versus 75.9 IU l-1) along with a better seroconversion rate (87.5 versus 61.9%). However, the differences in vaccine dose between the two groups may also be a contributory factor. Our findings indicate that three doses of recombinant HB vaccine were invariably effective in eliciting a good immune response in previous non-responders to the four doses of plasma HB vaccine. Therefore, it is speculated that these young vaccinees who did not respond to four doses of plasma HB vaccine may not be real non-responders, but hyporesponders.

To determine the HLA-linked immune response gene that controls low responsiveness to hepatitis B surface antigen (HBsAg), HLA typing was performed in 33 initial non-responders (male:female = 23:10, age 1.5–46 years) who had poor antibody response (anti-HBs < 10 mIU ml−1) after four doses of plasma-derived hepatitis B vaccine. Of 33 initial non-responders, 26 received two additional doses of either the same vaccine (n = 18) or recombinant hepatitis B vaccine (n = 8) and returned for anti-HBs measurement. At 1 month after the sixth dose, anti-HBs was still

This study compared safety, tolerability, and immunogenicity of the Oka/Merck varicella vaccine and VARILRIX [Oka-RIT strain SmithKline Beecham Biologicals] in healthy children 12-24 months of age. Subjects were randomized in this double blind study to receive either a single dose of Oka/Merck varicella vaccine, (approximately 50,000 plaque forming units (PFU), Group A or approximately 16,000 PFU, Group B) or 1 dose of VARILRIX, (approximately 40,000 PFU/dose, Group C). Safety profiles in each treatment group were similar. The proportions of subjects achieving a 6-week postvaccination titeror = 5 gpELISA units in Groups A, B or C were 97.1, 95.2 and 85.6%, respectively.