Effect of small bowel bacterial overgrowth on the immunogenicity of single-dose live oral cholera vaccine CVD 103-HgR.

Several live oral vaccines (polio, bovine rotavirus, CVD 103-HgR cholera) are less immunogenic in developing than in industrialized countries. It was hypothesized that proximal small bowel bacterial overgrowth (common in children in less developed countries but rare in industrialized settings) diminishes the vibriocidal antibody response to CVD 103-HgR. In total, 202 fasting Santiago schoolchildren aged 5-9 years had lactulose breath H2 tests to detect proximal small bowel bacteria 1 day before ingesting CVD 103-HgR. Florid small bowel overgrowth was observed in 10 (5.6%) of 178 analyzable children. In children with florid overgrowth, vibriocidal seroconversion differed little from other children (60% vs. 67%), but the geometric mean titer was lower (160 vs. 368; P=.25). By logistic regression, increased peak breath H2 at small bowel time points was associated with diminished seroconversion (P=.04), as was the interaction of H2 value and weight (children >25 kg had lower seroconversion rates among subjects with heaviest overgrowth).

Palatability, reactogenicity and immunogenicity of engineered live oral cholera vaccine CVD 103-HgR in Chilean infants and toddlers.

BACKGROUND: Live oral cholera vaccine CVD 103-HgR is well-tolerated and immunogenic when administered to adults, school age children and preschool children in a single 5 x 10(9) colony-forming unit dose. Because elicitation of immune responses after administration of a single dose is exceptional for any oral vaccine in any age group, CVD 103-HgR was used as a probe to investigate the clinical acceptability, practicality and immunogenicity of this vaccine in infants and toddlers 3 to 17 months of age. METHODS: The study was undertaken successively in 12- to 17-month-olds (n = 104), 7- to 11-month-olds (n = 106) and 3- to 5-month-olds (n = 102). One-half of the subjects were randomly allocated to receive vaccine and the other one-half to receive placebo, in double blind fashion. After 2 weeks of double blind follow-up, all subjects received a dose of vaccine. Vibriocidal antibody titers were measured on coded sera collected at baseline and 2 weeks after each dosing. The buffered vaccine "cocktail" had a volume of 100 ml; subjects who ingested > or =70 ml were considered fully vaccinated. FINDINGS: Only 37% of subjects overall (25% of 3- to 5-month-olds) ingested > or =70 ml of the cocktail. The vaccine was well-tolerated with no significant differences in the rate or severity of adverse reactions after ingestion of vaccine vs. placebo. Seroconversion after ingestion of a single dose of CVD 103-HgR was similar in fully vaccinated subjects (66%) and in those who ingested a smaller fraction of the vaccine cocktail (63%). Of subjects who ingested two doses, 5 of 118 excreted vaccine organisms on Day 7 after the first dose vs. 0 of 118 after the second dose. INTERPRETATION: Single dose oral CVD 103-HgR is well-tolerated and immunogenic in infants even when a partial dose is ingested. The buffered vaccine cocktail that is readily imbibed by older children is not appealing to young infants, and improved vaccine formulations and delivery vehicles for immunizing infants must be sought.

Expanded safety and immunogenicity of a bivalent, oral, attenuated cholera vaccine, CVD 103-HgR plus CVD 111, in United States military personnel stationed in Panama.

To provide optimum protection against classical and El Tor biotypes of Vibrio cholerae O1, a single-dose, oral cholera vaccine was developed by combining two live, attenuated vaccine strains, CVD 103-HgR (classical, Inaba) and CVD 111 (El Tor, Ogawa). The vaccines were formulated in a double-chamber sachet; one chamber contained lyophilized bacteria, and the other contained buffer. A total of 170 partially-immune American soldiers stationed in Panama received one of the following five formulations: (a) CVD 103-HgR at 10(8) CFU plus CVD 111 at 10(7) CFU, (b) CVD 103-HgR at 10(8) CFU plus CVD 111 at 10(6) CFU, (c) CVD 103-HgR alone at 10(8) CFU, (d) CVD 111 alone at 10(7) CFU, or (e) inactivated Escherichia coli placebo. Among those who received CVD 111 at the high or low dose either alone or in combination with CVD 103-HgR, 8 of 103 had diarrhea, defined as three or more liquid stools. None of the 32 volunteers who received CVD 103-HgR alone or the 35 placebo recipients had diarrhea. CVD 111 was detected in the stools of 46% of the 103 volunteers who received it. About 65% of all persons who received CVD 103-HgR either alone or in combination had a fourfold rise in Inaba vibriocidal titers. The postvaccination geometric mean titers were comparable among groups, ranging from 450 to 550. Ogawa vibriocidal titers were about twice as high in persons who received CVD 111 as in those who received CVD 103-HgR alone (600 versus 300). The addition of CVD 111 improved the overall seroconversion rate and doubled the serum Ogawa vibriocidal titers, suggesting that the combination of an El Tor and a classical cholera strain is desirable. While CVD 111 was previously found to be well tolerated in semiimmune Peruvians, the adverse effects observed in this study indicate that this strain requires further attenuation before it can be safely used in nonimmune populations.

Economisation of vaccination against Haemophilus influenzae type b: a randomised trial of immunogenicity of fractional-dose and two-dose regimens.

BACKGROUND: The cost of Haemophilus influenzae type b (Hib) conjugate vaccines has limited their use in non-industrialised countries. To identify more economical vaccination schedules, we carried out a randomised trial of the immunogenicity of alternative regimens to the standard three-dose series. METHODS: 627 Chilean infants were randomly allocated to one of four regimens with either Hib polysaccharide-tetanus toxoid conjugate vaccine (PRP-T) or Hib oligosaccharide-diphtheria mutant toxoid conjugate vaccine (PRP-CRM197), for a total of eight groups. All infants receive diphtheria-tetanus-pertussis (DTP) vaccine at ages 2, 4, and 6 months. The regimens included three full doses, three fractional doses consisting of one half or one third of the full dose, and a regimen of two full doses (at age 4 and 6 months). The primary outcome was the proportion of infants with serum anti-polyribosylribitol phosphate (PRP, the type b capsular polysaccharide) concentrations of 0.15 microg/mL or more at age 8 months. FINDINGS: 93% (95% CI 85-98) of infants vaccinated with three full doses of PRP-T or PRP-CRM197 (95% CI 84-98) achieved anti-PRP concentrations of 0.15 microg/mL or more at age 8 months, compared with 91% (83-96) to 100% (95-100) of infants immunised with any fractional-dose regimen. Of the infants vaccinated with two doses of PRP-T or PRP-CRM197, 99% (93-100) and 87% (77-93) developed anti-PRP concentrations of 0.15 microg/mL or more, respectively. INTERPRETATION: 91% (83-96) to 100% (95-100) of infants immunised with one-half or one-third of a full dose of Hib conjugate developed protective antibody concentrations. Carrier priming with DTP may make two-dose schedules an option in some places. These alternative regimens could bring the cost of Hib vaccines within reach of countries that currently cannot afford them.

Evaluation of a bivalent (CVD 103-HgR/CVD 111) live oral cholera vaccine in adult volunteers from the United States and Peru.

To provide optimum protection against classical and El Tor biotypes of Vibrio cholerae O1, a single-dose, oral cholera vaccine was developed by combining two live, attenuated vaccine strains, CVD 103-HgR (classical, Inaba) and CVD 111 (El Tor, Ogawa). The vaccines were formulated in a double-chamber sachet; one chamber contained lyophilized bacteria, and the other contained buffer. In the first study, 23 U.S. adult volunteers received CVD 103-HgR at 10(8) CFU plus CVD 111 at 10(8), 10(7), or 10(6) CFU, CVD 111 alone at 10(7) CFU, or placebo. In the second study, 275 Peruvian adults were randomized to receive CVD 103-HgR at 10(9) CFU plus CVD 111 at 10(9) or 10(8) CFU, CVD 111 alone at 10(9) CFU, CVD 103-HgR alone at 10(9) CFU, or placebo. Three of 15 U.S. volunteers who received CVD 111 at 10(7) or 10(8) CFU developed mild diarrhea, compared to none of 4 who received CVD 111 at 10(6) CFU and 1 of 4 who received placebo. Twelve (63%) of 19 vaccine recipients shed the El Tor vaccine strain. All but one volunteer developed significant Ogawa and Inaba vibriocidal antibody titers. Volunteers who received CVD 111 at 10(7) CFU had geometric mean Ogawa titers four to five times higher than those of volunteers who received the lower dose. In the second study, all dosage regimens were well tolerated in Peruvians. About 20% of volunteers who received CVD 111 at the high dose excreted the El Tor organism, compared to 7% in the low-dose group. CVD 111 was detected in the stools of two placebo recipients, neither of whom had symptoms or seroconverted. In all vaccine groups, 69 to 76% developed fourfold rises in Inaba vibriocidal antibodies. Among those who received the bivalent vaccine, 53 to 75% also developed significant rises in Ogawa vibriocidal antibodies. We conclude that it is feasible to produce a single-dose, oral bivalent vaccine that is safe and immunogenic against both biotypes (El Tor and classical) and both serotypes (Inaba and Ogawa) of cholera for populations in both developed and developing parts of the world.

No adverse impact on protection against pertussis from combined administration of Haemophilus influenza type b conjugate and diphtheria-tetanus toxoid-pertussis vaccines in the same syringe.

To assess whether combining a Haemophilus influenzae type b conjugate vaccine (PRP-T) and diphtheria-tetanus toxoid-pertussis (DTP) vaccine in a single syringe would impact adversely the antibody response and clinical protection conferred by pertussis vaccine, surveillance and a nested serosurvey were conducted among infants in a large-scale evaluation of PRP-T in Santiago. Infants received either combined PRP-T/DTP or DTP only at 2, 4, and 6 months of age. At 8 months, pertussis agglutinin, anti-pertussis toxin, and anti-filamentous hemagglutinin antibody levels in the PRP-T/DTP (137.7, 23.1, and 12.2, respectively) and DTP (142.9, 20.6, and 13.0, respectively) groups were comparable. The incidence of pertussis was similar among infants assigned to health centers administering combined PRP-T/DTP and those administering DTP alone (13.1 vs. 12.2 cases/10(5) child-years). Combined PRP-T/DTP vaccine did not diminish protection against pertussis.

Large scale, postlicensure, selective vaccination of Chilean infants with PRP-T conjugate vaccine: practicality and effectiveness in preventing invasive Haemophilus influenzae type b infections.

BACKGROUND: Haemophilus influenzae type b (Hib) conjugate vaccines have demonstrated an impressive impact in diminishing Hib disease in industrialized countries. However, their high cost prompts nonindustrialized countries to corroborate their effectiveness under local conditions before considering their programmatic implementation. Such a postlicensure evaluation of vaccine effectiveness was undertaken in Chile. METHODS: After its licensure in Chile polyribosylribitol phosphate-tetanus toxoid protein conjugate vaccine (PRP-T), combined with diphtheria-tetanus-pertussis vaccine, was introduced into the Expanded Program on Immunization schedules in 36 health centers throughout metropolitan Santiago for 12 months, whereas 35 similar health centers administered only diphtheria-tetanus toxoid-pertussis vaccine. Bacteriologic surveillance data for invasive Hib cases collected over the ensuing 30 months were analyzed. RESULTS: In an intent-to-vaccinate (effectiveness) analysis, PRP-T provided 90.2% protection (95% confidence interval, 74.5 to 100%) against invasive Hib disease (40 vs. 4 cases, P < 0.001). Vaccine effectiveness was 91.3% against meningitis (22 vs. 2 cases) and 80% against pneumonia and empyema (10 vs. 2 cases, P = 0.039). Vaccine efficacy among infants who received all three doses of PRP-T was 91.7% (95% confidence interval, 64.8 to 100%). CONCLUSIONS: Programmatic use of Hib conjugate vaccine administered in combination with diphtheria-tetanus-pertussis vaccine constitutes a highly effective and practical intervention in Chile, a newly industrializing country.

Safety, immunogenicity, and excretion pattern of single-dose live oral cholera vaccine CVD 103-HgR in Peruvian adults of high and low socioeconomic levels.

Groups of 122 Peruvian adults of low socioeconomic level (SEL) and 125 of high SEL received a randomly allocated 5 x 10(9)- or 5 x 10(8)-CFU dose of CVD 103-HgR live oral cholera vaccine or a placebo. The vaccine was well tolerated. Vibriocidal seroconversions occurred in 78% of high-SEL and 72% of low-SEL subjects who ingested the high dose and in 78 and 49%, respectively, of those who received the low dose.

[Tolerance and immunogenicity of an oral dose of CVD 103-HgR, a live attenuated Vibrio cholerae 01 strain: a double-blind study of Chilean adults]. / Tolerancia e inmunogenicidad de una dosis oral de la cepa de Vibrio cholerae 01, viva-atenuada, CVD 103--HgR: estudio doble ciego en adultos chilenos.

CVD 103-HgR is an attenuated, AB+, live, recombinant vaccine strain, developed by deletion of the toxA gen in a virulent Vibrio cholerae 01, Inada classical strain (569B). In phase II studies conducted to date, CVD 103-HgR has been well tolerated and immunogenic in volunteers from both industrialized countries and cholera-endemic areas. In this study of safety, immunogenicity and excretion, 81 Chilean adults were randomly allocated to receive, in a double blind fashion, a single oral dose of 5 x 10(9) FU of CVD 103-HgR or placebo, (5 x 10(9) heat-killed E. Coli K12 organisms), in 100 ml of buffered water. Side effects were assessed by daily visits to the participants. Immunogenicity, (vibriocidal seroconversion), was investigated in blood drawn before and on days 8 and 28 after immunization, while stool cultures to assess excretion of the vaccine strain were performed on specimens obtained on days 1 and 7. None of the participants, (40 vaccinees and 41 placebo recipients), experienced untoward effects during 30 minutes of close surveillance after ingestion of the preparation; upon follow up, neither adverse events were more frequently reported by the vaccinees. 34/40 vaccinees, and 2/41 participants receiving placebo had a significant raise, (> = fourfold), in their vibriocidal titers; (85 vs 2%, p < 0.001). The peak postimmunization geometric mean titer, (222), was ten fold higher than the baseline vibriocidal titer. The vaccine strain was recovered in stool cultures from 8 participants, one of them excreted the strain in both specimens. We conclude that CVD-103-HgR is safe and immunogenic in Chilean adults.

Serologic response to Helicobacter pylori among children and teenagers in northern Chile.

The serologic response to Helicobacter pylori was determined in 388 children and teenagers living in Iquique, Chile by using an IgG enzyme-linked immunosorbent assay. Serum antibody levels, as measured by optical density, correlated strongly with age. Increases in the mean antibody level were seen primarily after age five, with rates of seropositivity increasing to > or = 70% among teenagers. The reasons for this age-related pattern of acquisition of infection remain to be determined.

Seroprevalence of Helicobacter pylori in Chile: vegetables may serve as one route of transmission.

Helicobacter pylori infection is very common in Chilean adults, but the age-related prevalence, risk factors for infection, and mode of transmission in Chilean children are unknown. An ELISA was used to test for H. pylori antibodies in 1815 Chileans < 35 years of age. Seropositivity was > 60% in lower socioeconomic groups. H. pylori seropositivity correlated with increased age, low socioeconomic status, and consumption of uncooked vegetables by use of a logistic regression analysis. Risk factors that reached marginal significance were consumption of uncooked shell-fish, female sex, and residence in Santiago. Although multiple modes of transmission for H. pylori undoubtedly exist, prior studies have suggested that contamination of irrigation water by raw sewage (and the subsequent contamination of vegetables that are eaten uncooked) is a key factor in the transmission of enteric pathogens in Chile; H. pylori may be transmitted by a similar route.

Plasmids in Salmonella typhi in Lima, Peru, 1987-1988: epidemiology and lack of association with severity of illness or clinical complications.

A prospective study was conducted to better characterize the epidemiology of plasmid-bearing strains of Salmonella typhi in an endemic area of Lima, Peru, and to determine if plasmids were associated with specific manifestations of typhoid fever. Of 228 S. typhi isolated from patients at Cayetano Heredia University Hospital in Lima during 1987-1988, 76 (33%) contained plasmids. Ten different plasmid profiles were identified, with ten distinct plasmids present within these profiles. There was significant temporal clustering of isolates having common plasmid profiles. Two plasmids (both from the same isolate) carried antibiotic resistance genes. Two cryptic plasmids with approximate sizes of 55 and 65 kilobases (kb) appeared to be closely related, based on restriction endonuclease digestions and Southern blot analysis. An ampicillin resistance plasmid from a 1989 patient isolate differed by only a single restriction fragment from the cryptic 65-kb plasmid. No association was found between any plasmid or plasmid profile and severity or clinical manifestations of disease.

Rotavirus-specific breast milk antibody in two populations and possible correlates of interference with rhesus rotavirus vaccine seroconversion.

Milk was collected from 56 New York and 70 Venezuelan mothers participating in Rhesus rotavirus (RRV) pediatric vaccine trials. Plaque reduction neutralization antibody (PRNA) to RRV (VP7:3, VP4:RRV) and human P rotavirus (VP7:3, VP4:P) and epitope-blocking antibody to one RRV VP4 and VP7 epitope were determined. Controlling for postpartum age, more Venezuelan milk samples had detectable RRV and P PRNA, RRV VP4 epitope-blocking antibody (P less than or equal to .001), and higher RRV and P PRNA geometric mean titers (P = .01) than New York samples. Using a logistic regression model, both milk and infants' serum preimmunization RRV PRNA titers had a negative effect on seroconversion (P = .008 and .02, respectively). Only 25% (2/8) infants fed milk containing greater than or equal to 1:160 RRV PRNA seroconverted compared with 83% (5/6) fed milk containing less than 1:160 RRV PRNA (P = .1). Of milk samples containing greater than or equal to 1:160 RRV PRNA, seven (88%) of eight had greater than fourfold neutralizing activity against RRV versus P (P = .035), suggesting that VP4-specific milk antibodies may interfere with RRV seroconversion.

Effect of priming with carrier on response to conjugate vaccine.

To examine whether prior immunity against a carrier protein modulates the serological response to injected peptide haptens attached to the same carrier in man, baseline tetanus antitoxin levels in volunteers who received a malaria sporozoite peptide-tetanus toxoid conjugate vaccine were compared with post-vaccination IgM and IgG antibody titres against the sporozoite antigen. In tetanus-vaccinated North American recipients of low doses of conjugate vaccine there were significant dose-dependent negative correlations between these variables, which suggests that epitopic suppression may occur in man. In contrast, Venezuelans living in non-malarious areas and mostly naive to tetanus toxoid showed a notable IgM response to the sporozoite antigen. The findings indicate that epitopic suppression and immune enhancement occur in man, and that the specific immunological responses to conjugate peptide vaccines may be difficult to predict.