Immunity to pertussis 5 years after booster immunization during adolescence.

BACKGROUND: We conducted a 5-year follow-up study on the persistence of pertussis-specific antibody and cell-mediated immunity after booster immunization of adolescents aged 11-13 years with a tricomponent acellular pertussis vaccine (Boostrix; trials diphtheria-tetanus-acellular pertussis [Tdap]-004/030). METHODS: Cellular and humoral immunity to pertussis toxin (PT), filamentous hemagglutinin, and pertactin were measured in adolescents (age, 16 years) 5 years after booster immunization. Similar investigations were performed for control adolescents who had received only diphtheria and tetanus booster vaccination. RESULTS: Five years after pertussis booster vaccination, the geometric mean concentrations of immunoglobulin G (IgG) elicited by each of the 3 pertussis vaccine antigens decreased from 1-month and 3-year postvaccination levels, but with the exception of PT IgG, were still higher than the prevaccination levels. PT IgG levels were undetectable in 28% of the subjects, but 44% of those subjects still tested positive for cell-mediated immunity to PT. Filamentous hemagglutinin IgG and pertactin IgG levels were significantly higher in Tdap-boosted adolescents than in the control subjects. Antibody concentrations at 1 month after vaccination strongly predicted antibody persistence. Cell-mediated immunity levels to PT, filamentous hemagglutinin, and pertactin persisted above the prebooster levels measured 5 years earlier. CONCLUSIONS: The results of the present study of adolescents indicate that the interval between acellular pertussis booster immunizations might be extended beyond 5 years.

A randomized, double-blind study of the safety, transmissibility and phenotypic and genotypic stability of cold-adapted influenza virus vaccine.

BACKGROUND: Live attenuated influenza vaccine (LAIV; FluMist) is a trivalent vaccine containing cold-adapted influenza vaccine viruses that infect and replicate in cells lining the nasopharynx to induce immunity. Recovery of viruses (shedding) is measured by culture of nasal specimens. Shedding of vaccine viruses is not equated with transmission because transmission requires more virus than is detected in many nasal swabs. Previous studies with LAIV did not detect transmission to close contacts. The primary objective of this study was to estimate the probability of transmission to placebo contacts in a day care setting. METHODS: One hundred ninety-seven healthy children aged 9 to 36 months attending day care were randomized to receive vaccine or placebo. Postvaccination viral shedding, safety, genotype and phenotype of shed viruses and probability of transmission were assessed. RESULTS: Eighty percent of 98 vaccine recipients shed at least one vaccine strain. No clinically significant differences in solicited adverse events attributable to vaccine occurred; safety profiles were similar in both groups. Vaccine virus isolates retained their phenotypic characteristics (cold adaptation and temperature sensitivity) and did not revert at nucleotides known to confer an attenuating phenotype. There was one confirmed transmission of a vaccine strain to a single placebo recipient. According to the Reed-Frost model, the calculated probability of transmission to a child after contact with a single vaccinated child was 0.58% (95% confidence interval, 0-1.7%). There was no increased reactogenicity or other safety concerns in the recipient child. CONCLUSIONS: Young children in a day care setting had a high rate of shedding and a low rate of transmission. No clinically significant illness occurred among children who received vaccine or placebo or in the child to whom the vaccine virus was transmitted.

Pertussis-specific cell-mediated and humoral immunity in adolescents 3 years after booster immunization with acellular pertussis vaccine.

We evaluated pertussis-specific cell-mediated immunity (CMI) and humoral immunity in adolescents 3 years after they received an acellular pertussis booster immunization. Two hundred sixty-four adolescents were examined for immunoglobulin G antibodies, and 49 were examined for CMI against Bordetella pertussis antigens 40 months after receiving the booster. A control group of similarly aged adolescents who had received diphtheria and tetanus vaccination 3 years earlier was included for comparison. Pertussis-specific CMI persisted at greater than prebooster immunization levels. Although they had decreased by the 3-year follow-up, antibody levels remained significantly higher than prebooster immunization levels. Antibodies against pertussis antigens and CMI against filamentous hemagglutinin and pertactin were significantly higher in vaccinated adolescents than in control subjects. The acellular pertussis booster immunization provides long-term CMI and humoral immunity lasting for >or=3 years. The significantly higher immunity observed in the diphtheria, tetanus, and acellular pertussis vaccine recipients, compared with that in control subjects, indicates that these responses are more likely to have resulted from the booster immunization than from the boosting effects of natural B. pertussis infection.