Toward a new vaccine for pertussis.

To overcome the limitations of the current pertussis vaccines, those of limited duration of action and failure to induce direct killing of Bordetella pertussis, a synthetic scheme was devised for preparing a conjugate vaccine composed of the Bordetella bronchiseptica core oligosaccharide with one terminal trisaccharide to aminooxylated BSA via their terminal ketodeoxyoctanate residues. Conjugate-induced antibodies, by a fraction of an estimated human dose injected into young outbred mice as a saline solution, were bactericidal against B. pertussis, and their titers correlated with their ELISA values. The carrier protein is planned to be genetically altered pertussis toxoid. Such conjugates are easy to prepare, stable, and should add both to the level and duration of immunity induced by current vaccine-induced pertussis antibodies and reduce the circulation of B. pertussis.

Capsular polysaccharide vaccine for Group B Neisseria meningitidis, Escherichia coli K1, and Pasteurella haemolytica A2.

We reviewed the literature that is the basis for our proposal that (2→8)-α-Neu5Ac conjugates will be safe and effective vaccines for Group B meningococci (GBMs), Escherichia coli K1, and Pasteurella haemolytica A2. Although (2→8)-α-Neu5Ac is a virulence factor and a protective antigen of these three pathogens, it is also a component of normal tissues (neural cell adhesion molecule). Natural, anti-(2→8)-α-Neu5Ac present in most adults, vaccine-induced antibodies, and even high levels of spontaneously appearing monoclonal anti-(2→8)-α-Neu5Ac did not cause autoimmunity. Although it is not possible to prove a null hypothesis, there are no epidemiologic, serologic, immunologic, or clinical data to indicate that (2→8)-α-Neu5Ac antibodies will induce pathology or an autoimmune disease. No increased pathology caused by these antibodies was found, even in neonates and infants of mothers recovered from GBM meningitis. The lack of pathology mediated by anti-(2→8)-α-Neu5Ac may be explained by different presentations of (2→8)-α-Neu5Ac on bacterial and mammalian cells and by the unusual physicochemical properties of anti-(2→8)-α-Neu5Ac. Based on clinical and experimental data collected over 30 y and because (2→8)-α-Neu5Ac is an essential virulence factor and a protective antigen for GBM, E. coli K1, and P. haemolytica A2, protein conjugates of it are easy to prepare using inexpensive and plentiful ingredients, and they would be compatible with routinely administered infant vaccines, clinical studies of these conjugates should proceed.

Oligosaccharide conjugates of Bordetella pertussis and bronchiseptica induce bactericidal antibodies, an addition to pertussis vaccine.

Pertussis is a highly contagious respiratory disease that is especially dangerous for infants and children. Despite mass vaccination, reported pertussis cases have increased in the United States and other parts of the world, probably because of increased awareness, improved diagnostic means, and waning vaccine-induced immunity among adolescents and adults. Licensed vaccines do not kill the organism directly; the addition of a component inducing bactericidal antibodies would improve vaccine efficacy. We investigated Bordetella pertussis and Bordetella bronchiseptica LPS-derived core oligosaccharide (OS) protein conjugates for their immunogenicity in mice. B. pertussis and B. bronchiseptica core OS were bound to aminooxylated BSA via their terminal Kdo residues. The two conjugates induced similar anti-B. pertussis LPS IgG levels in mice. B. bronchiseptica was investigated because it is easier to grow than B. pertussis. Using B. bronchiseptica genetically modified strains deficient in the O-specific polysaccharide, we isolated fractions of core OS with one to five repeats of the terminal trisaccharide, having at the nonreducing end a GlcNAc or GalNAc, and bound them to BSA at different densities. The highest antibody levels in mice were elicited by conjugates containing an average of 8-17 OS chains per protein and with one repeat of the terminal trisaccharide. Conjugate-induced antisera were bactericidal against B. pertussis, and the titers correlated with ELISA-measured antibody levels (r = 0.74). Such conjugates are easy to prepare and standardize; added to a recombinant pertussis toxoid, they may induce antibacterial and antitoxin immunity.

Effects of infection and disease with Mycobacterium tuberculosis on serum antibody to glucan and arabinomannan: two surface polysaccharides of this pathogen.

BACKGROUND: The role of the surface capsular polysaccharides (CPs) of Mycobacterium tuberculosis (Mtb) in the pathogenesis of infection and disease, as well their potential for use as diagnostic reagents and vaccine antigens, are unknown. METHODS: Serum antibody to two CPs of Mtb, arabinomannan (AM) and glucan (Glu), were studied in samples from 52 18-74 year-old HIV-seronegative, immunocompetent individuals in Houston Texas. The effects of Mtb exposure, infection and disease upon the levels of antibodies to these CPs were assessed. Subjects were grouped according to the standard international classification. RESULTS: IgA anti-Glu levels were significantly higher in the active and treated TB compared to a group that was PPD-negative without TB exposure history (p<0.05). Antibodies against AM demonstrated a similar pattern, with the exception that IgG anti-AM was higher in groups who had active TB or previously documented active TB, and IgA anti-AM was higher in subjects with previously documented active TB compared to the level in an unexposed, PPD-negative group (p<0.05). Serum IgG anti-Glu levels were higher in subjects with active TB or previously documented active TB than in the unexposed PPD-negative group, but the differences were not significant. CONCLUSIONS: These data suggest that the evaluation of antibody responses to the CP of Mtb may have utility for TB serodiagnosis, and that vaccines designed to induce humoral responses to TB CPs should be tested for their capacity to evoke anti-tuberculosis protective immunity.

A bicomponent Plasmodium falciparum investigational vaccine composed of protein-peptide conjugates.

There is yet no licensed vaccine against malaria, a serious human disease affecting mostly children, with an annual death rate of about one million. Plasmodia, the malaria-causing parasites, have two obligatory hosts: mammals or birds, in which they multiply asexually, and mosquitoes with sexual multiplication. The most common and serious type of malaria is caused by Plasmodium falciparum. The circumsporozoite protein (CSP), a major surface antigen of sporozoites, is a protective antigen. A unique feature of P. falciparum CSP is its large central domain composed of over 30 tetrapeptide repeats of Asn-Ala-Asn-Pro (NANP). Several NANP peptide-protein conjugates were tested clinically but elicited a low level of CSP antibodies for a short duration. To provide a CSP-based candidate vaccine, we investigated recombinant CSP and NANP conjugates of various peptide lengths, with different N-terminal amino acids, bound at different ratios to various carrier proteins. Injected into mice, CSP alone and CSP or NANP conjugates induced antibodies with booster responses and were positive by the sporozoite immunofluorescent assay. The use of the mosquito stage P. falciparum ookinete surface protein, Pfs25, cross-linked onto itself as a carrier for NANP, induced in mice high levels of uniquely long-lasting antibodies to both vaccine components with secondary biological activities, that will provide immunity to liver infection by sporozoites and block transmission by mosquitoes.

Synthetic oligosaccharides as tools to demonstrate cross-reactivity between polysaccharide antigens.

Escherichia coli O148 is a nonencapsulated enterotoxigenic (ETEC) Gram negative bacterium that can cause diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome in humans. The surface-exposed O-specific polysaccharide (O-SP) of the lipopolysaccharide of this bacterium is considered both a virulence factor and a protective antigen. It is built up of the linear tetrasaccharide repeating unit [3)-α-L-Rhap-(1→2)-α-D-Glcp-(1→3)-α-D-GlcNAcp-(1→3)-α-L-Rhap-(1→] differing from that of the O-SP of Shigella dysenteriae type 1 (SD) only in that the latter contains a D-Galp residue in place of the glucose moiety of the former. The close similarity of the O-SPs of these bacteria indicated a possible cross-reactivity. To answer this question we synthesized several oligosaccharide fragments of E. coli O148 O-SP, up to a dodecasaccharide, as well as their bovine serum albumin or recombinant diphtheria toxin conjugates. Immunization of mice with these conjugates induced anti-O-SP-specific serum IgG antibody responses. The antisera reacted equally well with the LPSs of both bacteria, indicating cross-reactivity between the SD and E. coli O148 O-SPs that was further supported by Western-blot and dot-blot analyses, as well as by inhibition of binding between the antisera and the O-SPs of both bacteria.

Synthesis, characterization, and immunogenicity in mice of Shigella sonnei O-specific oligosaccharide-core-protein conjugates.

Shigellosis, an enteric disease, is on the World Health Organization's priority prevention list. In one study, the Shigella sonnei O-specific polysaccharide (O-SP)-protein conjugate showed 72% protection against disease in Israeli army recruits exposed to high rates (8-14%) of infection. The protection was related to vaccine-induced IgG anti-O-SP levels. Synthetic oligosaccharides of Shigella dysenteriae type 1, bound by their reducing ends to a carrier protein ("sun"-type configuration), induced significantly higher antibody levels than the native O-SP bound to protein by multiple-point attachments ("lattice"-type configuration). Attempts to synthesize the S. sonnei O-SP based oligosaccharides were not successful. Here, we describe the isolation, characterization, and conjugation of low-molecular-mass O-SP-core (O-SPC) fragments. The O-SPC fragments were bound by their reducing ends similar to the preparation of the synthetic S. dysenteriae type 1 conjugates. The O-SPC conjugates used oxime linkages between the terminal Kdo residues at the reducing ends of the S. sonnei saccharides and aminooxy linkers bound to BSA or a recombinant diphtheria toxin. The coupling reaction was carried out at a neutral pH and room temperature. IgG antibody levels induced in young outbred mice by the S. sonnei O-SPC conjugates were significantly higher then those elicited by the O-SP conjugates. Accordingly, we propose to evaluate clinically these conjugates.

Comparative long-term adverse effects elicited by invasive group B and C meningococcal infections.

BACKGROUND: Given the identity between Neisseria meningitidis serogroup B (MenB) capsular polysaccharide (polysialic acid; PSA) and PSA found on neural cell adhesion molecules, it has been proposed that infection with MenB or vaccination with PSA may be associated with subsequent autoimmune or neurological disease. METHODS: We conducted 2 studies. The first was a retrospective nationwide study of invasive meningococcal disease (IMD) in Iceland (with 541 subjects) during the period 1975-2004, and we cross referenced this cohort with databases with respect to subsequent diagnosis of autoimmune disorders. A follow-up study involving 120 survivors of IMD was performed. The study included 70 patients with a history of MenB and 50 patients with N. meningitidis serogroup C (MenC) infection, who served as control subjects. Participants answered standardized questionnaires (Beck's Depression Inventory [BDI] II, Depression Anxiety Stress Scales [DASS], and Patient Health Questionnaire [PHQ]), and serum levels of immunoglobulin (Ig) G against MenB and MenC capsular polysaccharides were measured. RESULTS: The nationwide cohort had 9166 patient-years of follow up. No evidence of increased autoimmunity was found to be associated with MenB, compared with MenC. In the follow-up study, patients were evaluated 16.6 years after the infection, representing 2022 patient-years of observation. Comparable rates of most complications were recorded, but MenC infections were associated with arthritis (P = .008) and migraine headaches (P = .01) more frequently than were MenB infections. No difference was observed with respect to scores on BDI-II, DASS, or PHQ. IgG anti-MenB and anti-MenC capsular polysaccharide levels were not related to patient complaints. CONCLUSIONS: This study does not support the hypothesis that MenB infection may predispose to autoimmunity. MenC infections are associated with a higher prevalence of arthritis and migraine headaches. No evidence of antibody-associated pathology was detected at long-term follow-up.

Saccharides cross-reactive with Bacillus anthracis spore glycoprotein as an anthrax vaccine component.

Bacillus anthracis is a spore-forming bacterium that causes anthrax in humans and in other mammals. The glycoprotein BclA (Bacillus collagen-like protein of anthracis) is a major constituent of the exosporium, the outermost surface of B. anthracis spores. The glycosyl part of BclA is an oligosaccharide composed of 2-O-methyl-4-(3-hydroxy-3-methylbutanamido)-4,6-dideoxy-d-glucose, referred to as anthrose, and three rhamnose residues. A structure similar to anthrose, 4-(3-hydroxy-3-methylbutanamido)-4,6-dideoxy-d-glucose is found in the side chain of the capsular polysaccharide (CPS) of Shewanella spp. MR-4. Under certain growth conditions the bacteria produce a variant CPS lacking one methyl group on the hydroxybutyrate, 4-(3-hydroxybutanamido)-4,6-dideoxy-d-glucose. Contrary to anthrose, neither of the Shewanella CPSs is 2-O methylated. Here, we report that both Shewanella CPS variants react with anti-B. anthracis spore sera. We also found that these antisera reacted with flagellae of Pseudomonas syringae, reported to be glycosylated with a similar terminal saccharide, 4-(3-hydroxybutanamido)-4,6-dideoxy-2-O-methyl-d-glucose. Sera produced by immunization with Shewanella or P. syringae cells bound to B. anthracis spores but not to Bacillus cereus spores in a fluorescent microscopy assay. These experiments show that methylation of the anthrose at the O-2 of the sugar ring and at the C-3 of 3-hydroxybutyrate are not essential for induction of cross-reactive antibodies. We report the preparation, characterization, and antibody responses to protein conjugates of the two variants of Shewanella CPS. Both conjugates induced antibodies that bound to both Shewanella CPS variants by ELISA and to B. anthracis spores, as detected by fluorescent microscopy. We propose the use of Shewanella CPS conjugates as a component of an anthrax vaccine.

Pertussis vaccine: a critique.

A critical level of serum IgG pertussis toxin antibody is both essential and sufficient to confer individual and herd immunity to pertussis. Monocomponent pertussis toxoid conferred such immunity in Sweden and in Denmark. We refute the notion that filamentous hemagglutinin, pertactin, and fimbriae add to the immunity conferred by pertussis toxoid and describe the artifact created when efficacy is estimated for multicomponent pertussis vaccines. Lastly, the genetically-inactivated mutant pertussis toxoid is safer, more immunogenic, and should be more effective than the current chemically-inactivated pertussis toxin.

Risk of adverse birth outcome after group B meningococcal disease: results from a Danish national cohort.

BACKGROUND: Group B meningococcal (GBM) disease induces antibodies that react in vitro with neural cell adhesion molecules in fetal brain tissue. Because IgG antibodies to GBM cross the placenta, the authors investigated whether women with a previous GBM disease had an increased risk of giving birth to preterm or to stillborn infants and whether the live-born children had an increased risk of birth defects. METHODS: Data were obtained from 4 national registries in the period 1974-2005 to form 2 cohorts: (1) 1422 women with confirmed GBM disease, and (2) their 502 firstborn children. RESULTS: Overall, there was no increased risk of preterm or stillbirths among the first cohort. Among the children, there was no increased risk of being born small for the gestational age, having birth defects (OR: 1.00; 95% CI: 0.53-1.90), diseases of the nervous system (HR: 0.38; 95% CI: 0.08-1.74), or any diseases within the first 3 years of life (HR: 1.06; 95% CI: 0.78-1.45) compared to births from a reference population with prior group C meningococcal disease. CONCLUSIONS: The results do not support the proposal that GBM is associated with immunoreactive disease that may affect the health of the offspring and are consistent with previous findings that GBM disease is not associated with an increased risk of autoimmune disease.

Use of a Staphylococcus aureus conjugate vaccine in patients receiving hemodialysis.

BACKGROUND: In patients with decreased resistance to infection, Staphylococcus aureus is a major cause of bacteremia and its complications. The capsular polysaccharides are essential for the pathogenesis of and immunity to S. aureus infection and are targets for vaccines. METHODS: In a double-blind trial involving patients with end-stage renal disease who were receiving hemodialysis, we evaluated the safety, immunogenicity, and efficacy of a vaccine with S. aureus type 5 and 8 capsular polysaccharides conjugated to nontoxic recombinant Pseudomonas aeruginosa exotoxin A. Between April 1998 and August 1999, 1804 adult patients at 73 hemodialysis centers were randomly assigned to receive a single intramuscular injection of either vaccine or saline. IgG antibodies to S. aureus type 5 and 8 capsular polysaccharides were measured for up to two years, and episodes of S. aureus bacteremia were recorded. Efficacy was estimated by comparing the incidence of S. aureus bacteremia in the patients who received the vaccine with the incidence in the control patients. RESULTS: Reactions to the vaccine were generally mild to moderate, and most resolved within two days. The capsular polysaccharides elicited an antibody response of at least 80 microg per milliliter (the estimated minimal level conferring protection) in 80 percent of patients for type 5 and in 75 percent of patients for type 8. The efficacy during weeks 3 to 54 was only 26 percent (P=0.23). However, between weeks 3 and 40 after vaccination, S. aureus bacteremia developed in 11 of 892 patients in the vaccine group who could be evaluated for bacteremia, as compared with 26 of 906 patients in the control group (estimate of efficacy, 57 percent; 95 percent confidence interval, 10 to 81 percent; nominal P=0.02). CONCLUSIONS: In patients receiving hemodialysis, a conjugate vaccine can confer partial immunity against S. aureus bacteremia for approximately 40 weeks, after which protection wanes as antibody levels decrease.

Vaccination with Shigella flexneri 2a conjugate induces type 2a and cross-reactive type 6 antibodies in humans but not in mice.

Shigella flexneri (S. flexneri) 6 has emerged as an important cause of shigellosis. Our efficacy study of Shigella sonnei and S. flexneri 2a O-specific polysaccharide (O-SP) conjugates in 1-4year-olds had too few S. flexneri 2a cases for efficacy evaluation but surprisingly showed protection of 3-4year-olds, S. flexneri 2a-recipients, from S. flexneri 6 infection. To investigate this cross-protection antibodies to both Shigella types were investigated in all sera remaining from previous studies. Twenty to 30% of 3-44year-old humans injected with S. flexneri 2a conjugate responded with ≥4-fold increases of IgG anti type 6, p<0.00001. The specificity of these antibodies was shown by inhibition studies. S. flexneri 6 infection of 2 children induced besides S. flexneri 6, also S. flexneri 2a antibodies, at levels of S. flexneri 2a vaccinees. S. flexneri 2a antibodies induced by S. flexneri 6 conjugates could not be studied since no such conjugate was assessed in humans and mice responded almost exclusively to the O-SP of the injected conjugate, with no cross-reactive antibodies. Our results indicate induction of cross-reactive protective antibodies. The O-acetylated disaccharide shared by S. flexneri 6 and 2a O-SPs, is the likely basis for their cross-reactivity. S. flexneri 6 O-SP conjugates, alone and in combination with S. flexneri 2a, merit further investigation for broad S. flexneri protection.

Synthesis of octa- and dodecamers of D-ribitol-1-phosphate and their protein conjugates.

The bacterial cell-wall-associated teichoic acids contain predominantly D-ribitol residues interconnected by phosphodiester linkages. Because of their location, these antigens may be vaccine candidates as part of conjugate vaccines. Here, we describe the synthesis of extended oligomers of D-ribitol-1-phosphate linked to a spacer having an amino group at its terminus. The synthesis utilized a fully protected D-ribitol-phosphoramidite that was oligomerized in a stepwise fashion followed by deprotection. The free oligomers were connected to bovine serum albumin using oxime chemistry. Thus, the ribitol phosphate oligomers were converted into keto derivatives, and the albumin counterpart was decorated with aminooxy groups. Reaction of the functionalized saccharide and protein moieties afforded conjugates having up to 20 ribitol phosphate chains.

Antibodies against Haemophilus influenzae type b capsular polysaccharide and tetanus toxoid before and after a booster dose of the carrier protein nine years after primary vaccination with a protein conjugate vaccine.

IgG antibodies against Haemophilus influenzae type b (Hib) capsular polysaccharide (CPS) and tetanus toxoid (TT) were measured for 53 children, 10 years of age, before and 1 month after a booster dose of diphtheria-tetanus vaccine (DT). All children had been vaccinated at 3, 5 and 12 months of age with DT and a Hib-TT conjugate. Geometric mean concentrations of Hib CPS serum IgG antibody were 4.16 and 4.30 microg/mL before and after the DT booster, respectively. The geometric mean concentration of TT IgG antibody increased from 0.09 IU/mL to 4.58 IU/mL (P < 0.001). Hib CPS IgG levels remained well above protective titers for 9 years after 3 doses of Hib-TT appropriately spaced in infancy. A booster dose of TT did not affect Hib CPS antibody concentrations but induced a pronounced IgG response against TT.

Staphylococcus aureus types 5 and 8 capsular polysaccharide-protein conjugate vaccines.

BACKGROUND: Staphylococcus aureus, the first or second most common pathogen isolated from patients, is capsulated; there are at least 12 capsular types, and types 5 and 8 comprise approximately 85% of blood. Types 5 and 8, composed of a trisaccharide repeat unit including a mannose uronic acid and 2 fucoses, are non-immunogenic. As protein conjugates, they induce opsonophagocytic antibodies that confer type-specific active and passive protection in mice. METHODS: A phase II study of patients with end-stage renal disease showed that these conjugates induced approximately one third of the immunoglobulin G antibody of healthy individuals. Increasing the dose to 100 microg of polysaccharide induced levels similar to that in healthy individuals injected with 25 microg. RESULTS: In a double-blinded randomized and controlled study of patients undergoing renal dialysis, the conjugates induced statistically significant protection against bacteremia for as long as 10 months after immunization. The estimated protective level was 80 microg Ab/mL. At re-injection approximately 2 years later, 83 of 83 recipients responded with protective levels. CONCLUSIONS: Conjugate vaccine-induced antibodies to the types 5 and 8 capsular polysaccharide antibodies of S aureus prevent bacteremia caused by this pathogen. The extent and duration of conjugate-induced immunity can be extended by re-immunization approximately 1 year later. Studies of patients undergoing cardiovascular surgery who would be immunized with the staphylococcus conjugates when they are immunologically intact are planned.

Safety and immunogenicity of Shigella sonnei-CRM9 and Shigella flexneri type 2a-rEPAsucc conjugate vaccines in one- to four-year-old children.

BACKGROUND AND OBJECTIVE: Shigella conjugate vaccines have been shown to be safe, immunogenic and efficacious in adult volunteers. We have now investigated the safety and immunogenicity of investigational Shigella sonnei and Shigella flexneri 2a conjugate vaccines in 1- to 4-year-old children, the age group at greatest risk for shigellosis. METHODS: The O-specific polysaccharides of S. sonnei and S. flexneri 2a, the two most common shigellae from patients in Israel, were bound to medically useful carrier proteins to form conjugates. Eighty healthy 1- to 4-year-olds were randomized to receive two 0.5-ml im injections 6 weeks apart of either S. sonnei-CRM(9) or S. flexneri 2a-rEPA(succ). Blood was taken before, 6 weeks after the first injection, 4 weeks after the second injections and 2 years after immunization for assay of IgG anti-lipopolysaccharide, diphtheria toxin and Pseudomonas aeruginosa exotoxin A antibodies by enzyme-linked immunosorbent assay. RESULTS: During an 8-day surveillance period after each immunization, low fever (37.8-39.0 degrees C) lasting only 24 to 48 h occurred in 2 of 40 recipients after the first injection and 4 of 40 recipients after the second injection of S. flexneri 2a-rEPA(succ) and in 2 of 38 of S. sonnei-CRM(9) after the second injection; no fever was detected after the first injection. Liver function tests were normal in all vaccinees. S. sonnei-CRM(9) elicited a >4-fold rise in IgG anti-LPS in 92.1% and S. flexneri 2a-rEPA(succ) in 85% (P < 0.0001) after the second injection; both conjugates elicited type-specific booster responses. At 2 years the geometric mean concentrations of both IgG anti-lipopolysaccharides were significantly higher than preimmunization levels. A >4-fold rise of IgG anti-diphtheria (65.8%) and IgG anti-ETA (77.5%) was observed. CONCLUSION: These experimental Shigella conjugate vaccines were safe and immunogenic in 1- to 4-year-old children.

Future vaccine development at NICHD.

Using published data and the results of our studies, we hypothesized that a critical level of serum IgG antibodies to the surface structures of invasive pathogens (capsular polysaccharides of Haemophilus influenzae type b, pneumococcus, meningococcus, Salmonella typhi, Escherichia coli, and Staphylococcus aureus, the O-specific polysaccharide LPS domain of the LPS of Shigella, non-typhoidal Salmonella, and E. coli, and the capsular polypeptide of Bacillus anthraces) confer immunity to these pathogens. Covalent attachment to a protein increases their immunogenicity and bestows T-cell properties to these antigens. We have also shown that a critical level of serum IgG antibodies to pertussis toxin alone induces immunity on both an individual and on a community basis (herd immunity) to Bordetella pertussis. It is likely that all the above conjugates and pertussis toxoid will be incorporated into vaccines for routine infant immunization.

Experience with monocomponent acellular pertussis combination vaccines for infants, children, adolescents and adults--a review of safety, immunogenicity, efficacy and effectiveness studies and 15 years of field experience.

Combination vaccines containing a monocomponent acellular pertussis (aP) vaccine, manufactured at Statens Serum Institut (SSI), Denmark, have successfully controlled Bordetella pertussis infections in Denmark since 1997. The efficacy of this aP vaccine was 71% in a double-blind, randomised and controlled clinical trial. Its safety and immunogenicity have been demonstrated in infants, children, adolescents and adults. In approximately 500,000 children it was effective against pertussis requiring hospitalisation (VE: 93% after 3 doses) and against pertussis not requiring hospitalisation (VE: 78% after 3 doses). IgG antibodies against pertussis toxin (IgG anti-PT) response rates after booster vaccination of adults with tetanus, diphtheria and aP combination vaccine (TdaP) were considerably higher for this monocomponent aP vaccine containing 20µg pertussis toxoid, inactivated by hydrogen peroxide (92.0%), than for two multicomponent aP vaccines inactivated by formaldehyde and/or glutaraldehyde: 3-component aP with 8µg pertussis toxoid (77.2%) and 5-component aP with 2.5µg pertussis toxoid (47.1%), without compromising the safety profile. In Denmark where this monocomponent aP vaccine has been the only pertussis vaccine in use for 15 years, there has been no pertussis epidemic since 2002 (population incidence 36 per 100,000), in contrast to neighbouring countries, where epidemics have occurred. This monocomponent aP vaccine can be used in combination vaccines for primary and booster vaccination against pertussis in all age groups and is an important tool for successful pertussis control.