Alum-adjuvanted Vaccine Research Articles

Emulsified nanoparticles containing inactivated influenza virus and CpG oligodeoxynucleotides critically influences the host immune responses in mice.

BackgroundAntigen sparing and cross-protective immunity are regarded as crucial in pandemic influenza vaccine development. Both targets can be achieved by adjuvantation strategy to elicit a robust and broadened immune response. We assessed the immunogenicity of an inactivated H5N1 whole-virion vaccine (A/Vietnam/1194/2004 NIBRG-14, clade 1) formulated with emulsified nanoparticles and investigated whether it can induce cross-clade protecting immunity.Methodology/Principal FindingsAfter formulation with PELC, a proprietary water-in-oil-in-water nanoemulsion comprising of bioresorbable polymer/Span®85/squalene, inactivated virus was intramuscularly administered to mice in either one-dose or two-dose schedule. We found that the antigen-specific serum antibody responses elicited after two doses of non-adjuvanted vaccine were lower than those observed after a single dose of adjuvanted vaccine, PELC and the conventional alum adjuvant as well. Moreover, 5 µg HA of PELC-formulated inactivated virus were capable of inducing higher antibodies than those obtained from alum-adjuvanted vaccine. In single-dose study, we found that encapsulating inactivated virus into emulsified PELC nanoparticles could induce better antibody responses than those formulated with PELC-adsorbed vaccine. However, the potency was rather reduced when the inactivated virus and CpG (an immunostimulatory oligodeoxynucleotide containing unmethylated cytosine-guanosine motifs) were co-encapsulated within the emulsion. Finally, the mice who received PELC/CpG(adsorption)-vaccine could easily and quickly reach 100% of seroprotection against a homologous virus strain and effective cross-protection against a heterologous virus strain (A/Whooper swan/Mongolia/244/2005, clade 2.2).Conclusions/SignificanceEncapsulating inactivated H5N1 influenza virus and CpG into emulsified nanoparticles critically influences the humoral responses against pandemic influenza. These results demonstrated that the use of PELC could be as antigen-sparing in preparation for a potential shortage of prophylactic vaccines against local infectious diseases, in particular pandemic influenza. Moreover, the cross-clade neutralizing antibody responses data verify the potential of such adjuvanted H5N1 candidate vaccine as an effective tool in pre-pandemic preparedness.

An inactivated Vero cell-grown Japanese encephalitis vaccine formulated with Advax, a novel inulin-based adjuvant, induces protective neutralizing antibody against homologous and heterologous flaviviruses

Advax is a polysaccharide-based adjuvant that potently stimulates vaccine immunogenicity without the increased reactogenicity seen with other adjuvants. This study investigated the immunogenicity of a novel Advax-adjuvanted Vero cell culture candidate vaccine against Japanese encephalitis virus (JEV) in mice and horses. The results showed that, in mice, a two-immunization, low-dose (50 ng JEV antigen) regimen with adjuvanted vaccine produced solid neutralizing immunity comparable to that elicited with live ChimeriVax-JE immunization and superior to that elicited with tenfold higher doses of a traditional non-adjuvanted JEV vaccine (JE-VAX; Biken Institute) or a newly approved alum-adjuvanted vaccine (Jespect; Novartis). Mice vaccinated with the Advax-adjuvanted, but not the unadjuvanted vaccine, were protected against live JEV challenge. Equine immunizations against JEV with Advax-formulated vaccine similarly showed enhanced vaccine immunogenicity, confirming that the adjuvant effects of Advax are not restricted to rodent models. Advax-adjuvanted JEV vaccine elicited a balanced T-helper 1 (Th1)/Th2 immune response against JEV with protective levels of cross-neutralizing antibody against other viruses belonging to the JEV serocomplex, including Murray Valley encephalitis virus (MVEV). The adjuvanted JEV vaccine was well tolerated with minimal reactogenicity and no systemic toxicity in immunized animals. The cessation of manufacture of traditional mouse brain-derived unadjuvanted JEV vaccine in Japan has resulted in a JEV vaccine shortage internationally. There is also an ongoing lack of human vaccines against other JEV serocomplex flaviviruses, such as MVEV, making this adjuvanted, cell culture-grown JEV vaccine a promising candidate to address both needs with one vaccine.

The Protection Potential of an Alum-Adjuvanted F1 Protein in Dry Powder against Plague in Mice

Aluminum hydroxide is the only adjuvant for use in human vaccines. The commercial alum-adjuvanted vaccines are formulated as liquid without exception. We prepared an alum-adjuvanted dry powder vaccine and demonstrated that it provided good protection for plague. The preparation strategy is simple and effective and can be carried out in a large scale. The dry powder vaccine can be quickly reconstituted using sterile water for injection. The dry powder vaccines have potential advantages over liquid vaccines, including good stability and extended shelf life.

Infections, vaccines and autoimmunity

The associations between exposure to infectious agents and the development of autoimmune diseases have been established in numerous studies and almost every autoimmune disease has been linked to one infection or another. Different infectious agents, namely bacteria, viruses and parasites, were found to be related to autoimmunity via several mechanisms such as molecular mimicry, epitope spreading, polyclonal activation of B-cells and finally by bystander activation of T-cells and antigen presenting cells. The links between infections and autoimmunity are complex, on the one hand many infectious agents were found to be pathogenic, while on the other hand, others might induce protection from autoimmunity. In addition, many patients suffering from autoimmune diseases are especially vulnerable for infections, due to the underlying disease and the frequent use of immunosuppressive therapy. Thus, vaccination to prevent and reduce infectious morbidity and mortality is recommended for this group of patients. Alas, vaccines which contain infectious antigens, either attenuated or recombinant, may induce, although rarely, autoimmunity via similar ‘infectious’ mechanisms. Furthermore vaccines contain other excipients such as adjuvants and preservatives which may induce an immune mediated response. Adjuvants are included in most human vaccines in order to increase the protective immune response to infectious antigens, however in recent years many adjuvants were found to induce autoimmunity by themselves. Similarly to the autoimmune manifestation following silicone implantation, especially following rupture and leak of silicone, previously termed ‘adjuvant disease’, it seems also that adjuvants which are included in human vaccines may rarely induce autoimmunity. Recently, a new disease of autoimmune nature was defined and termed macrophagic myofaciitis. This syndrome appears in subjects who are genetically susceptible following vaccination with alum adjuvanted vaccines, and it is characterized by an active lesion with evidence of alum mediated reaction at the site of inoculation. Genetic susceptibility is a cardinal factor in the mosaic of autoimmunity and may determine the individual response to a certain infectious agents, a drug or a vaccine. Fortunately, it seems that genetic and other factors render a low rate of susceptibility to autoimmunity following vaccination, and therefore vaccines’ beneficial effects outweigh the risks of autoimmunity for the vast majority of individuals. In this special issue of Lupus we have assembled a collection of manuscripts describing the multifaceted associations between infections, vaccines and autoimmune diseases, as well as the mechanisms by which autoimmunity is inflicted and the genetic susceptibility related to these unique interactions.

Safety and immunogenicity of whole-virus, alum-adjuvanted whole-virus, virosomal, and whole-virus intradermal influenza A/H9N2 vaccine formulations

Avian influenza H9N2 viruses are considered as a pandemic threat. We assessed the safety and immunogenicity of fourteen H9N2 vaccine formulations. A randomized, phase I trial was done in 353 adults, aged 18–82 years. Subjects received two doses of A/Hong Kong/1073/99 (H9N2) whole-virus, alum-adjuvanted whole-virus, virosomal, or intradermal whole-virus vaccine at four doses (1.7, 5, 15 or 45 μg haemagglutinin). Sera were obtained before and three weeks after each vaccination (days 0, 21, and 42) for haemagglutination–inhibition (HAI) and neutralization assays. All formulations were well tolerated. Pre-vaccination sera from subjects aged below or above 40 years had baseline antibody to H9N2 in 1% and 16% of samples. Compared to intramuscular whole-virus vaccine, alum-adjuvanted vaccine was more immunogenic, intradermal vaccine was comparable, and virosomal vaccine less immunogenic. Among subjects under 40 years, two doses (45, 15, and 5 μg) of alum-adjuvanted vaccine achieved seroprotective HAI titres in 50%, 41%, and 39% respectively, and neutralization seroconversions in 83%, 82%, and 78% of recipients. Among subjects over 40 years, one dose (45, 15, and 5 μg) of alum-adjuvanted vaccine achieved seroprotective HAI titres in 50%, 25% and 0% respectively, and neutralization seroconversions in 88%, 63% and 63% of recipients. Among immunologically naive subjects under 40 years, two doses of vaccine are required and alum-adjuvanted vaccines were most immunogenic. Among immunologically primed subjects over 40 years, one dose of whole-virus or alum-adjuvanted vaccine induced immune responses; the second dose provided less additional benefit. However, no vaccine formulation satisfied all European regulatory criteria for pandemic vaccines.

Rapid immunity to vaccination with woodchuck hepatitis virus surface antigen using cationic liposome–DNA complexes as adjuvant

Complexes of cationic liposomes and non-coding DNA (CLDC) have shown promise as vaccine adjuvant. Using the woodchuck animal model of hepatitis B virus (HBV) infection, the immunogenic effects of CLDC were evaluated following vaccination with three doses of woodchuck hepatitis virus surface antigen (WHsAg) adjuvanted with either CLDC or conventional alum and administered intramuscularly (im) or subcutaneously (sc). IM vaccination with WHsAg and CLDC elicited antibodies earlier, in more woodchucks, and with higher titers than WHsAg and alum. After two vaccine doses, antibody titers were higher following im than sc administration. Woodchucks administered two vaccine doses sc received the third vaccine dose im, and antibody responses reached titers comparable to those elicited by im administration. Following the second vaccine dose, im vaccination with WHsAg and CLDC induced T cell responses to WHsAg and selected WHs peptides and expression of the leukocyte surface marker CD8 and of the Th1 cytokines interferon-gamma and tumor necrosis factor alpha in woodchucks. T cell responses and CD8/cytokine expression were diminished in woodchucks from the other groups suggesting that this vaccine regimen induced a skew toward Th1 immune responses. The present study in woodchucks demonstrates that CLDC-adjuvanted WHsAg vaccine administered im resulted in a more rapid induction of humoral and cellular immune responses compared to conventional, alum-adjuvanted WHsAg vaccine. While less rapid, the immune responses following sc administration can prime the im immune responses. This adjuvant activity of CLDC over alum may be beneficial for therapeutic vaccination in chronic HBV infection.

A prime–boost vaccination of mice with heterologous H5N1 strains

We evaluated the priming effect of an H5N1 pandemic vaccine in a mouse model to investigate strategies for influenza pandemic vaccination. For priming, an alum-adjuvanted inactivated whole H5N1 vaccine (NIBRG-14, clade 1) was used. As booster vaccines, several formulations of Indo05/05/2005(H5N1)PR8-IBCDC-RG2 vaccines (clades 2–1) were evaluated, including split, whole, alum-adjuvanted split, and alum-adjuvanted whole vaccines. Any type of booster vaccination elicited a significant HI antibody response despite the difference in antigenicity between the priming and booster vaccines. The split vaccine elicited a much stronger booster response than the alum-adjuvanted whole vaccine. When the mice were primed with the H1N1 or H3N2 vaccines, this did not affect the booster response to the H5N1 vaccine. These results indicated that an alum-adjuvanted whole vaccine is able to confer immunological memory to haemagglutinin even if the primed and boosted vaccine strains are in different clades and, once vaccinated, a split vaccine is preferred to evoke recall responses.

Pre-clinical evaluation of a novel nanoemulsion-based hepatitis B mucosal vaccine.

BackgroundHepatitis B virus infection remains an important global health concern despite the availability of safe and effective prophylactic vaccines. Limitations to these vaccines include requirement for refrigeration and three immunizations thereby restricting use in the developing world. A new nasal hepatitis B vaccine composed of recombinant hepatitis B surface antigen (HBsAg) in a novel nanoemulsion (NE) adjuvant (HBsAg-NE) could be effective with fewer administrations.Methodology and Principal FindingsPhysical characterization indicated that HBsAg-NE consists of uniform lipid droplets (349+/−17 nm) associated with HBsAg through electrostatic and hydrophobic interactions. Immunogenicity of HBsAg-NE vaccine was evaluated in mice, rats and guinea pigs. Animals immunized intranasally developed robust and sustained systemic IgG, mucosal IgA and strong antigen-specific cellular immune responses. Serum IgG reached ≥106 titers and was comparable to intramuscular vaccination with alum-adjuvanted vaccine (HBsAg-Alu). Normalization showed that HBsAg-NE vaccination correlates with a protective immunity equivalent or greater than 1000 IU/ml. Th1 polarized immune response was indicated by IFN-γ and TNF-α cytokine production and elevated levels of IgG2 subclass of HBsAg-specific antibodies. The vaccine retains full immunogenicity for a year at 4°C, 6 months at 25°C and 6 weeks at 40°C. Comprehensive pre-clinical toxicology evaluation demonstrated that HBsAg-NE vaccine is safe and well tolerated in multiple animal models.ConclusionsOur results suggest that needle-free nasal immunization with HBsAg-NE could be a safe and effective hepatitis B vaccine, or provide an alternative booster administration for the parenteral hepatitis B vaccines. This vaccine induces a Th1 associated cellular immunity and also may provide therapeutic benefit to patients with chronic hepatitis B infection who lack cellular immune responses to adequately control viral replication. Long-term stability of this vaccine formulation at elevated temperatures suggests a direct advantage in the field, since potential excursions from cold chain maintenance could be tolerated without a loss in therapeutic efficacy.

Immunogenicity and safety of a novel formalin-inactivated and alum-adjuvanted candidate subunit vaccine for mumps

While an attenuated vaccine against mumps has played a role in controlling the epidemic of this disease worldwide, some problems with efficacy and safety of the vaccine are still present. In the work described here, a novel mumps vaccine with good immunity and safety was developed by selecting an antigen component of the mumps virus. The results suggest that this purified antigen vaccine is immunogenic in animals and is capable of inducing a specific neutralizing antibody response against viral HN, but not against other viral proteins. The clinical and pathological observations after challenge of vaccinated rhesus monkeys indicated further that the immune response induced by this vaccine provided complete protection from wild-type virus infection. Furthermore, the immunological analysis and clinical observation of experimental monkeys that were immunized with the vaccine, followed by infection with wild-type virus, suggest that no abnormal changes in expression of inflammatory cytokines and no clinical allergic reaction were found at 1 month after challenge.

Concomitant Administration of a Virosome-Adjuvanted Hepatitis A Vaccine With Routine Childhood Vaccines at Age Twelve to Fifteen Months: A Randomized Controlled Trial

The objectives of this trial were to test for noninferiority of a virosomal hepatitis A virus (HAV) vaccine (Epaxal) coadministered with routine childhood vaccines compared with Epaxal given alone and to an alum-adjuvanted HAV vaccine (Havrix Junior) coadministered with routine childhood vaccines. Healthy children 12- to 15-month-old were randomized to receive either a pediatric dose (0.25 mL) of Epaxal coadministered with DTPaHibIPV, oral polio vaccine, and measles-mumps-rubella vaccine (n = 109; group A), or Epaxal given alone (n = 105; group B), or Havrix Junior coadministered with DTPaHibIPV, oral polio vaccine, and measles-mumps-rubella vaccine (n = 108; group C). A booster dose was given 6 months later. Anti-HAV antibodies were tested before and 1 month after each vaccination. Safety was assessed for 1 month after each vaccination. Solicited adverse events were assessed for 4 days after each vaccination. : HAV seroprotection rates (> or =20 mIU/mL) at 1 and 6 months after first dose were: A: 94.2% and 87.5%, B: 92.6% and 80.0%, C: 78.2% and 71.3%, respectively (A versus C: P < 0.001 and P = 0.017 at month 1 and 6, respectively). The respective geometric mean concentrations were: A: 51 and 64 mIU/mL, B: 49 and 59 mIU/mL, C: 33 and 37 mIU/mL (A versus C: P < 0.001 at both time points). All groups achieved 100% seroprotection after the booster dose. The geometric mean concentrations after the booster dose were 1758, 1662, and 1414, for groups A, B and C, respectively (A versus C: P = 0.15). No clinically significant reduction in immune response to all concomitant vaccine antigens was seen. All vaccines were well tolerated. : Coadministration of pediatric Epaxal with routine childhood vaccines showed immunogenicity and safety equal to Epaxal alone as well as to Havrix Junior. After first dose, Epaxal was significantly more immunogenic than Havrix Junior.

RLJ-NE-299A: A new plant based vaccine adjuvant

Alum has been in use since long as an adjuvant for vaccines. However, its use as a vaccine adjuvant offers limitation in supporting cell mediated response. Therefore, a new plant based product RLJ-NE-299A from Picrorhiza kurroa reported for its immunostimulatory activity, has been explored for its potential as an alternative adjuvant. In order to compare the adjuvant activity with alum, antigen-specific immune responses were evaluated following immunization with a formulation containing hepatitis B surface antigen (HBsAg) adjuvanted with RLJ-NE-299A and alum in mice. The adjuvant RLJ-NE-299A up-regulated remarkably the expression of Th1 cytokines IL-2, IL-12, IFN-γ, TNF α and Th2 cytokine IL-4 in lymph node cell cultures after 2 weeks of primary immunization with HBsAg. Further, the levels of both immunoglobulins IgG2a (Th1) and IgG1 (Th2) subtypes increased profoundly in blood sera of mice immunized with HBsAg/RLJ-NE-299A. The results indicated that RLJ-NE-299A has strong potential to increase both cell mediated and humoral immune responses and is capable of sustaining the total antigen-specific antibody response. Besides, the RLJ-NE-299A provides a signal to gear up both CD4 helper cells (Th1 and Th2) and CD8 cells populations, which may have important implications for vaccination against hepatitis B virus. Variable doses of RLJ-NE-299A (0.312–40 μg) containing vaccine antigen (HBsAg) were well tolerated with optimum T cell response at 2.5 μg/ml. Not only this, the adjuvant was also able to induce cellular immune responses to HBsAg as evidenced by Th1 and Th2 cytokines upregulation, which enabled mice to overcome the unresponsiveness to antigen HBsAg encountered with alum-adjuvanted vaccine in otherwise non-responding mice population. The study presents evidence that the HPLC standardized fraction RLJ-NE-299A, is an adjuvant of choice over alum in improving and maintaining the improved immune status against HBsAg, and may also prove useful adjuvant candidate with other vaccine antigens, too.

Clevudine Therapy with Vaccine Inhibits Progression of Chronic Hepatitis and Delays Onset of Hepatocellular Carcinoma in Chronic Woodchuck Hepatitis Virus Infection

We examined a rational approach to therapy of chronic hepatitis B virus (HBV) infection that utilized the reduction of viral load combined with appropriately timed immune modulation/stimulation. In a placebo-controlled study, chronic woodchuck hepatitis virus (WHV) carrier woodchucks received clevudine (L-FMAU), previously shown to have especially potent and sustained antiviral activity in woodchucks, for 32 weeks followed by WHV surface antigen (WHsAg) alum-adjuvanted vaccine at 32, 36, 40 and 48 weeks. Clevudine induced significant reductions in viraemia, surface antigenaemia, hepatic WHV nucleic acids, and hepatic core and surface antigens. Viral replication markers remained markedly suppressed in 75% of the clevudine-treated woodchucks following drug withdrawal, but remained at high levels in the vaccine monotherapy and placebo groups. Combination drug and vaccine therapy had benefits based on sustained reduction of viraemia, antigenaemia, and hepatic WHV DNA and RNA; inhibition of progression of chronic hepatitis; reduced frequency of chronic liver injury; and delayed onset of hepatocellular carcinoma (HCC). Combination therapy contributed to prevention of HCC in up to 38% of treated carriers, although the growth rate of established HCC was not affected. This study demonstrates enhanced benefits of combination chemo-immunotherapy against viral load and disease progression in chronic hepadnaviral infection, and provides a platform for further development of such treatment regimens.

Stabilization of Alum-Adjuvanted Vaccine Dry Powder Formulations: Mechanism and Application

Studies were performed to elucidate the mechanism of alum gel coagulation upon freezing and drying and its relationship to vaccine potency loss and to develop a novel freeze-drying process for the production of stable alum-adjuvanted vaccine formulations suitable for conventional needle injection and epidermal powder immunization (EPI). The alum hydroxide-adjuvanted hepatitis-B surface antigen (Alum-HBsAg) and the alum phosphate-adjuvanted diphtheria and tetanus toxoids (Alum-DT) were dehydrated by freeze drying (FD), spray drying (SD), air drying (AD), or spray freeze drying (SFD). After drying by FD, SD, or AD, alum gels coagulated when examined by optical microscopy and particle size analysis. In addition, desorption of antigen molecules from the coagulated when examined by optical microscopy and particle size analysis. In addition, desorption of antigen molecules from the coagulated alum gel upon reconstitution appeared to be difficult, as indicated by attenuated band intensity on SDS-PAGE. In contrast, SFD alum gels turned a homogenous suspension upon reconstitution, suggesting minimal alum coagulation. In the mouse model, the in vivo immunogenicity of SFD Alum-HBsAg was preserved, whereas the FD Alum-HBsAg suffered significant immunogenicity loss. Grinding of coagulated FD Alum-HBsAg into smaller particles could partially recover the immunogenicity. In a guinea pig study using EPI, the SD Alum-DT formulation was not immunogenic, but the SFD Alum-DT formulations had a vaccine potency comparable to that of the untreated DT administered by I.M. injection. Overall, the relationship of coagulation of alum gel upon reconstitution and the loss of vaccine potency was established in this study. Alum gels became highly coagulated after dehydration by spray drying and traditional freeze-drying processes. However, freezing rate played a critical role in preserving the adjuvant effect of alum and fast freezing decreased the tendency of alum coagulation. Spraying the alum gel into liquid nitrogen represents the fastest freezing rate achievable and resulted in no discernible alum coagulation. Therefore, SFD presents a novel and effective drying process for alum-adjuvanted vaccine formulations and is particularly valuable for dry powder applications such as EPI.

Immune responses to hepatitis B surface antigen following epidermal powder immunization.

Langerhans cells in the epidermis of skin are potent antigen-presenting cells that trigger the immune system to respond to invading microorganisms. We have previously shown that epidermal powder immunization with a powdered inactivated influenza virus vaccine, by targeting the Langerhans cell-rich epidermis, was more efficacious than deeper tissue injection using a needle and syringe. We now report enhanced humoral and cellular immune responses to recombinant hepatitis B surface antigen following epidermal powder immunization. We observed that epidermal powder immunization with unadjuvanted hepatitis B surface antigen elicited an antibody titre equivalent to that induced by the alum-adjuvanted vaccine delivered by intramuscular injection, suggesting that epidermal powder immunization can overcome the need for adjuvantation. We demonstrated that synthetic CpG oligonucleotides (CpG DNA) could be coformulated with hepatitis B surface antigen and delivered by epidermal powder immunization to further augment the antibody response and modulate T helper cell activities. Epidermal powder immunization of hepatitis B surface antigen formulated with CpG DNA formulations resulted in 1.5-2.0 logs higher IgG antibody titres than alum-adjuvanted commercial vaccines administered by intramuscular injection. Formulation of hepatitis B surface antigen with CpG DNA elicited an augmented IgG2a antibody response and increased frequency of IFN-gamma secreting cells. In addition, CpG DNA was found to activate epidermal Langerhans cells and stimulate the production of TNF-alpha and IL-12 cytokines by epidermal cells, explaining its strong adjuvant activity following epidermal powder immunization. These results show that epidermal powder immunization is a safe and effective method to deliver hepatitis B surface antigen and the addition of new adjuvants, such as CpG DNA, may further enhance the efficacy of this vaccine.

Antibody response to an eleven valent diphtheria- and tetanus-conjugated pneumococcal conjugate vaccine in Filipino infants.

Pneumococcal conjugate vaccines are intended to provide effective protection against pneumococcal infections, but very little information on antibody responses in infants living in countries with high pneumococcal disease burden exists. In this study 50 healthy Filipino infants were enrolled at a village health center in Cabuyao to receive 11-valent diphtheria- and tetanus-conjugated pneumococcal vaccine at 6, 10 and 14 weeks of age (primary series) simultaneously with diphtheria-tetanus-whole cell pertussis/polyribosylribitol phosphate conjugated to tetanus toxoid, hepatitis B virus and oral poliovirus vaccines and at 9 months of age (booster dose) simultaneously with measles vaccine. The alum-adjuvanted study vaccine contained pneumococcal polysaccharide of serotypes 1, 4, 5, 7F, 9V, 19F and 23F conjugated to tetanus protein and pneumococcal polysaccharide of serotypes 3, 6B, 14 and 18C conjugated to diphtheria toxoid. Serum samples for enzyme immunoassay analyses were collected at 6, 10 and 14 weeks and 9 and 10 months of age. Very high geometric mean antibody concentrations (GMCs) against most pneumococcal serotypes were observed after the first three doses of vaccine (range, serotype 23F, 3.89 microg/ml to serotype 4, 23.41 microg/ml) with the exception of serotype 6B and 14, with GMCs of 1.12 and 2.18 microg/ml, respectively. The fourth dose increased the GMCs against most serotypes (range, serotype 14, 1.65 to serotype 19F, 33.43 microg/ml). The maternally derived antibodies did not decrease the response to the vaccine. This first pneumococcal conjugate vaccine study in Asia confirms that the 11-valent diphtheria- and tetanus-conjugated pneumococcal vaccine is highly immunogenic in Filipino infants. The GMCs against most pneumococcal serotypes were substantially higher than described with the same or other pneumococcal conjugate vaccines in other populations.

High immunogenicity and good tolerability of a new hepatitis A vaccine candidate

Immunogenicity and tolerability of a new formalin-inactivated, alum-adjuvanted whole virus vaccine against hepatitis A (VAQTA, MSD, West Point, USA) were evaluated by immunizing 52 healthy, anti-HAV negative volunteers with a 1 ml dose. A booster dose was given 6 months later. In these young adult vaccinees [27 males and 25 females, 19–34 (mean 26) years of age] VAQTA proved to be well tolerated and highly immunogenic. Two weeks after administration of one vaccine dose, all but one of the recipients (98%) had anti-HAV concentrations above the presumed minimum protective level of 10 IU l −1 with a geometric mean concentration (GMC) of 165 IU l −1. After 4 weeks, a 100% seroconversion rate could be demonstrated with a fourfold increase of the GMC to 728 IU l −1. Six months after vaccination, all but one of the 50 volunteers coming back for booster (98%) showed anti-HAV levels within the protective range. The antibody concentrations had decreased in the majority of vaccinees to a GMC of 362 IU l −1. The booster dose given at that time was shown to be very effective, leading to a pronounced rise of anti-HAV levels in all recipients with a 17-fold increase of the GMC to 6040 IU l −1. Six months after the booster, all vaccinees were still seropositive with a GMC of 3444 IU l −1. Higher antibody levels were found in females, the difference being significant 4 weeks and 6 months after vaccination and 4 weeks after booster. No serious local or systemic adverse reactions were observed.