Search

The effect of Haemophilus influenzae type b (Hib) meningococcal protein conjugate vaccine (Hib-OMPC; Merck, Sharp & Dohme) on oropharyngeal (OP) carriage of Hib was evaluated in Navajo and Apache Indian children, who are known to be at high risk for invasive Hib disease. We obtained 1423 OP swabs at well child visits from 1321 children 3 months to 4 years of age: 293 of the swabs were obtained from children before the administration of any Hib-OMPC; 1119 were taken after the primary vaccination series; and 11 after the booster dose. Swabs were tested for the presence of Hib capsular polysaccharide antigen by enzyme-linked immunosorbent assay. Forty of 1423 swabs were positive for Hib. Among the 40 positive swabs 5 (13%) were obtained from children who had received Hib-OMPC vaccine appropriate for age at swabbing, compared with 500 of 1383 (36%) of negative swabs. Children who were OP carriers of Hib were older than noncarriers (mean age, 13 and 9 months, respectively) and a greater proportion of carriers (48%) had symptoms of respiratory infection at the time of swabbing than noncarriers (30%). These variables were significantly related to increased risk of OP carriage of Hib when incorporated jointly in a logistic regression model: not vaccinated according to age (odds ratio 2.7, 95% confidence interval 1.00 to 7.05); increase of age in months (odds ratio 1.1, 95% confidence interval 1.02-1.10); and respiratory infection symptoms present (odds ratio 2.0, 95% confidence interval 1.06-3.77). Thus besides preventing invasive Hib disease, appropriate vaccination with Hib-OMPC appears to reduce OP carriage of Hib.

Testing for urinary excretion of capsular polysaccharide antigen was carried out in 40 four-month-old Navajo infants who had received injections of a Haemophilus influenzae type b Neisseria meningitidis outer membrane protein conjugate vaccine (PedvaxHIB; Merck, Sharp and Dohme Research Laboratories) as part of an ongoing efficacy trial of the vaccine. Urine from 12 placebo recipients was also analyzed. Urine samples were collected on the day of injection (the first voided urine following the injection) and 3, 7, 10, 14, 21 and 30 days later. All vaccine recipients had at least 1 positive specimen. Vaccine recipients excreted antigen for a median period of 14 days after injection. On the first day 54% of vaccinees excreted antigen. Antigen was excreted by 89% of vaccinees on Day 3, 79% on Day 7, 82% on Day 10, 64% on Day 14, 56% on Day 21 and 41% on Day 30. Urine from placebo recipients tested positive in 12% on Day 1, 18% on Day 3, none on Day 7, 14% on Day 10, 11% on Day 14, 10% on Day 21 and none on Day 30. The rate of positive test results was significantly higher among vaccine recipients than among controls. Physicians should not rely on urinary antigen detection tests for predicting the presence of invasive disease caused by H. influenzae type b in infants for at least 30 days after injections with this conjugate vaccine, and possibly longer.