Prevention of bacterial meningitis. Vaccines and chemoprophylaxis

The morbidity and mortality caused by bacterial meningitis remains significant despite advances in antimicrobial therapy and supportive care. Prevention of meningitis by routine immunization of infants, who are at greatest risk, offers the only practical way of reducing the incidence of this disease. Widespread use of the recently developed protein conjugate vaccines against Haemophilus influenzae type b by itself could reduce the incidence of bacterial meningitis in the U.S. by more than half. To prevent disease caused by the other pathogens, an effective vaccine against the group B meningococcus must be developed, and the immunogenicity of the pneumococcal and quadrivalent meningococcal vaccines should be improved. Until such time that universal immunization of infants with highly immunogenic vaccines is possible, continued efforts must focus on targeting immunization at high-risk individuals and using chemoprophylaxis to prevent secondary disease where indicated. Addendum: On October 4, 1990, the U.S. Food and Drug Administration licensed the praxis Haemophilus influenzae type b-protein conjugate vaccine (Hboc) for use in infants at 2, 4, and 6 months of age with a booster dose at 15-18 months. Physicians are directed to statements by the Immunizations Practices Advisory Committee and the American Academy of Pediatrics for official recommendations concerning its use.

Vaccination campaign against meningococcal disease in army recruits in Italy

A high attack rate (17.3/100,000) of meningococcal disease in army recruits in Italy, with 95% of the cases due to serogroup C, constituted the motivating factors to make bivalent serogroup A + C meningococcal vaccination compulsory by law for army recruits starting January 1987. Because the vaccine was given only to the new recruits entering the army, full coverage was not achieved until January 1988. Nearly 900,000 subjects (300,000 yearly) were vaccinated between January 1987 and December 1989. There were no reports of any untoward reactions to the vaccine. Of the 300,000 recruits in service each year, 52, 21, 15, 5 and 4 cases of the disease occurred in 1985, 1986, 1987, 1988 and 1989, respectively (P less than 0.001). Of the 24 cases occurring since the start of the vaccination, only two (due to serogroup C) were attributable to vaccine failure. The remaining cases were in unvaccinated recruits (15 cases) or were due to serogroups other than A or C (7 cases). The cumulative incidence of meningococcal serogroup C in the 600,000 vaccinated recruits during the period 1988-89 was 0.2/100,000 (1 case amongst 600,000 recruits), while the corresponding figure in the 600,000 unvaccinated recruits during the period 1985-6 was 11.3/100,000 (68 cases amongst 600,000 recruits) (P less than 0.001). The protective efficacy of the vaccine in 1987 was 91.2% (12 cases of meningococcal serogroup A and C disease from an average of 150,000 unvaccinated recruits observed for 1 year, and 1 case from the corresponding average of 150,000 vaccinated ones). In 1988 and in 1989 this figure could not be calculated because all recruits were vaccinated.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of meningococcal group A and C polysaccharide vaccine on nasopharyngeal carrier state

The effect of Neisseria meningitidis group A and C polysaccharide vaccine on nasopharyngeal carriage was studied in Italian army recruits. Throat swabs were cultured for N. meningitidis at the time of vaccination (one week after entry to service) and again three weeks later in a follow-up cohort of 98 men. At the first survey the overall carriage rate was 32% with 9% of isolates due to serogroup C, none to serogroup A and 17% to serogroup Y. At the second survey the overall carriage rate reached 52% (P less than 0.01); no isolate belonged to serogroup A or C, while serogroup Y reached 40% (P less than 0.01). The cumulative carriage rate was 65%. Out of the 64 carriers during the whole study period, only 7 (11%) belonged to the same serogroup during the two different surveys. The vaccination appears to influence the carriage rate of meningococcal specific serogroups. The inhibition of serogroups A and C is, however, offset by an increased prevalence of meningococci belonging to serogroup Y.

[Epidemiology of meningococcal infections and principles for the prevention of secondary cases]

The incidence of meningococcal infections undergoes secular variations with modifications in the distribution of identified serotypes. Rhinopharyngeal carriage of meningococci, common in the community, is the natural means of immunization. Prevalence of this carriage varies across age groups and communities, as well as according to whether or not cases are present in the community under study. Identified factors that promote transmission of the bacteria include crowded living conditions, poor socioeconomic conditions, and, more controversially, respiratory tract viral infections. Development of meningococcal infection usually occurs within seven days of onset of carriage. Secondary cases account for approximately 3% of meningococcal infections in France. The risk of development of secondary cases is increased in subjects sharing the patient's home or exposed to his or her rhinopharyngeal secretions. Prevention of these secondary cases rests on chemoprophylaxis and immunization. The qualities of antimicrobial agents proposed for chemoprophylaxis are discussed, with special emphasis on spiramycin and rifampin which are the most widely used. This study, which rests on French epidemiologic surveillance findings and data from a review of the literature, forms the basis for new French guidelines.

Surveillance and control of meningococcal meningitis epidemics in refugee populations

Epidemics of communicable diseases pose a direct threat to refugee and internally displaced populations, and could lead to high mortality rates and a disruption of basic health care services. Several large refugee populations live in regions of high meningococcal disease endemicity and their camps are at risk for outbreaks of meningococcal meningitis. Surveillance in these camps allows early detection and control of impending outbreaks. Confirmation of meningococcal disease can be performed under field conditions using simple techniques, such as latex agglutination. Isolates should be obtained for serogroup confirmation and antibiotic sensitivity studies at reference laboratories. Serogroup information is used to determine the risk of widespread epidemic disease and the utility of available vaccines. During epidemics, treatment regimens should be standardized, preferably with an effective single-dose antibiotic. Mass vaccination campaigns should be initiated, the populations at high risk being targeted for vaccination as quickly as possible. When the risk of epidemic disease is deemed to be high, preemptive vaccination may be warranted. Daily surveillance using a simple case definition is essential during an epidemic to determine the effectiveness of control measures and to delineate high-risk groups for vaccination or chemoprophylaxis. Many of these recommendations can be applied also to other populations in developing countries.

Immune status and response to immunization with polysaccharide vaccines of a healthy, congenitally asplenic woman

We describe the immune status of a congenitally asplenic, otherwise healthy and anatomically normal 30-year-old woman. As in surgically asplenic subjects, she had Howell-Jolly bodies in a blood smear, increased B lymphocyte and decreased T helper and suppressor lymphocyte percentages, and a slightly lower than average T helper/suppressor ratio. Because of the increased risk of infection with capsulate bacteria in asplenic patients, the subject was immunized with Pneumovax and meningococcal vaccine and her serum antibody responses were investigated. She was found to have subnormal IgG antibody titres which did not increase on immunization, although the subclass distribution of anti-pneumococcal antibody was normal with IgG2 predominating. IgM antibody titres were higher than in a pool of normal adult human sera, while IgA levels increased substantially as in normal subjects.

[Tetravalent anti-meningococcal vaccine: serologic and clinical evaluation]

Meningococcal disease is the only bacterial meningitis able to cause an epidemic and the mortality due to this disease is all but negligible; therefore the active immunization induced by a vaccine that includes a large portion of Neisseria meningitidis serogroups responsible for the immunization of subjects at risk. Tetravalent vaccine containing polysaccharides of the serogroups A, C, Y, W135 has given good results both for tolerability and immune response. Considering the epidemic situation in Italy, this vaccine could be an excellent strategy "to behead" possible epidemics and/or hyperendemics due to a known serogroups.

[Meningococcosis in Tunisia. Apropos of 80 cases]

Meningococcosis are nowadays an health problem because their incidence rate (38 cases/100,000 people in 1986 in Mahdia region) and a high death rate (40%) due to fulminating forms. At the occasion of a prospective study during the first six months of 1987, the authors report the emergence of C serogroup (21%), the smallness of A serogroup (6.50%) and the predominance of B serogroup (68%). Improving level of living, good prophylaxy based on spiramycin, development of use of meningococcal vaccine are advisable means to control epidemic outbreaks.

Comparative evaluation of potential components for group B meningococcal vaccine by passive protection in the infant rat and in vitro bactericidal assay

Seventeen monoclonal antibodies to one of three main cell surface antigens of Neisseria meningitidis group B were tested for protective efficacy in the infant rat using as challenge seven strains of different class 2/3 protein serotypes, class 1 protein (P1) subtypes and LPS immunotypes. Type-specific protection indicated both by a reduction of bacteraemia and meningitis and survival of the animals was regularly obtained with antibodies to the P1 protein and to LPS. By contrast, only one of seven antibodies to the serotype-specific class 2/3 protein was protective, even though four of them were highly bactericidal. The animal protection test and in vitro bactericidal assay were otherwise concordant. These data form important guidelines for the design of vaccines to prevent group B meningococcal infections.

Measurements of lipopolysaccharide (endotoxin) in meningococcal protein and polysaccharide preparations for vaccine usage

Lipopolysaccharide (LPS, i.e. endotoxin) present in meningococcal outer-membrane protein and polysaccharide preparations made for vaccine use was quantitated by a silver-stain method following SDS-PAGE. The reactivities of LPS in the preparations were also measured by rabbit pyrogenicity and Limulus amoebocyte lysate (LAL) assay. Although rabbit pyrogenicity and LAL assay are more sensitive than the silver stain method, the latter provided an actual amount of LPS present in the protein or in the polysaccharide. For a meningococcal protein preparation, rabbit pyrogenicity showed about one-tenth, and even less by LAL assay, of the actual amount of LPS. This is because protein-bound LPS in meningococcal protein preparations is about 10-fold less active in causing fever in rabbits, and 20- to 40-fold less active in the gelation of LAL than the same amount of a purified free LPS which is generally used as a reference in quantitating LPS in these two assays. As for the small amount of LPS present in a meningococcal polysaccharide preparation, similar LPS content was obtained when measured by the three methods suggesting that the LPS is not bound to the polysaccharide in contrast to that in the proteins mentioned above. The purified meningococcal LPS was pyrogenic in rabbits at 1 ng/kg.

Meningococcal disease in Canada. Surveillance summary to 1987

Meningococcal disease continues to occur in Canada at endemic levels, with minor fluctuations. The incidence of the disease, in general, has changed very little over the past 3 decades.

Invasive meningococcal disease: secondary spread in a day-care center

We have reported the epidemiologic investigation and subsequent control measures precipitated by the occurrence of two temporally related cases of invasive meningococcal disease in a single day-care center classroom. A review of the literature indicates that day-care center contacts of patients with invasive meningococcal disease are at increased risk for secondary spread of infection. Our experience emphasizes the importance of reporting cases to the local health department, implementing rifampin prophylaxis for appropriate contacts, and considering immunization in select circumstances. Rifampin is indicated for all cases of meningococcal disease as well.

Immune response to tetravalent meningococcal vaccine: opsonic and bactericidal functions of normal and properdin deficient sera

Neisseria meningitidis serogroup W-135 appears to be a fairly common cause of infection associated with properdin deficiency or dysfunction, and anticapsular antibodies might be protective in these patients. For this reason, bactericidal and opsonophagocytic activities for serogroup W-135 were investigated before and four weeks after vaccination of two properdin-deficient adults with tetravalent meningococcal vaccine. In addition, the response of IgM, IgG and IgA class antibodies to the serogroups A, C, Y and W-135 was determined by ELISA. There was no evidence of poor antibody responses in the properdin-deficient persons. Vaccination promoted classical pathway-mediated killing in serum and opsonization of serogroup W-135 to the same extent as that seen in vaccinated controls. The increase of alternative pathway-mediated killing in the properdin-deficient sera was moderate, but vaccination clearly enhanced alternative pathway-mediated opsonophagocytosis in the sera. It was also shown that vaccination markedly reduced the requirement for properdin in alternative pathway-mediated killing of the meningococci.

Meningococcal vaccine--do some children experience side effects?

In order to stop an outbreak of group A meningococcal meningitis, 130,000 Auckland children were immunised. During the month following vaccination there were 546 reports of unusual clinical events reported by parents and practitioners, together with 40 specialist paediatric assessments of children presenting with neurological symptoms. In 25 of these latter there was complete agreement between the history as presented by parents in the initial telephone report and the paediatrician's subsequent summarised history. Of the 546 reports, 217 either had too little detail for an assessment or the symptoms were clearly attributable to other causes. Of the remaining reports, there were 152 cases of fever with or without other symptoms; 85 were of rash and local reactions within 24h of vaccination; 63 reports were of headache, stiff neck and myalgia within 48h of vaccination. There were 92 reports of apparent peripheral nerve involvement, including 80 reports of unexplained weakness and 57 reports of paraesthesia or dysaesthesia. Both motor and sensory symptoms occurred in some children; none were permanent. The effects of adverse publicity during the campaign on the genesis of some symptoms is acknowledged, but the possibility that short term neurological symptoms occur after vaccination seems likely and has not been previously reported.

[Immunity against Neisseria meningitidis in different population groups]

The determination of titers of antibodies to A and C meningococcal capsular polysaccharides by means of passive hemagglutination, proved useful in the evaluation of the effects of vaccination in a group of adults. The determination of titers of antibodies to serogroup B polysaccharide showed differences among the groups of individuals subjected to different degrees of exposure to Neisseria meningitidis. A positive correlation was found between the titer of passive hemagglutination and the number of units of IgG antibodies to polysaccharide C, determined by immunoenzymatic analysis in a group of 10 people administered an experimental vaccine.

Group A meningococcal carriage in travelers returning from Saudi Arabia

In August 1987, an outbreak of group A meningococcal meningitis occurred during the annual pilgrimage to Mecca, Saudi Arabia, resulting in an attack rate among American pilgrims of 640 per 100,000. To determine risk factors for carriage, throat cultures were taken from passengers arriving on four consecutive flights from Saudi Arabia to the United States. Pilgrims were more likely to be group A meningococcal carriers than were nonpilgrims (relative risk, 11.1; 95% confidence interval, 3.7 to 33.1). Smoking, crowding, and meningococcal vaccination were not significantly associated with group A carriage. Pilgrims complaining of recent fever or sore throat, however, were more likely to be group A carriers, consistent with previous reports linking carriage and disease to preceding viral infections. Serogrouping of invasive meningococcal isolates can be used to monitor for indigenous transmission of this unusual strain in the United States, and we recommend routine vaccination of pilgrims to prevent future outbreaks of meningococcal disease.

Antibody response of adults to an aluminum hydroxide-adsorbed Neisseria meningitidis serotype 2b protein-group B polysaccharide vaccine

A group B Neisseria meningitidis serotype protein vaccine was studied clinically in adults. The vaccine comprised lipopolysaccharide-depleted outer membrane vesicles from a serotype 2b strain, 3006-M2, noncovalently complexed with group B meningococcal polysaccharide. Volunteers received 25 micrograms each of protein and polysaccharide administered intramuscularly either in 0.9% NaCl or adsorbed onto aluminum hydroxide on weeks 0 and 6. Most individuals experienced mild local reactions, but there were no systemic reactions. Both vaccine formulations stimulated antibodies to the outer membrane proteins of serotypes 2a:P1.2 and 2b:P1.2, but higher levels were achieved with the aluminum hydroxide-adsorbed vaccine after two immunizations. Vaccine-induced antibodies were primarily IgG and were bactericidal for both a serotype 2a and a serotype 2b strain. Induction of bactericidal antibodies has been shown to be a major predictor of protection against meningococcal disease.

Control of an outbreak of group C meningococcal meningitis with a polysaccharide vaccine

An outbreak of meningitis in Royal Air Force recruits due to Neisseria meningitidis Group C type PI, 2 gave the first opportunity for polysaccharide vaccine to be used for controlling such an outbreak in the U.K. The effect of the vaccine on an epidemic in a large recruit training centre was studied after chemoprophylaxis had failed. With the possible exception of one vaccinee, further cases did not arise among camp personnel. Vaccination was continued until the carriage rate of the epidemic strain among recruits leaving the camp had fallen from greater than 19 to less than 1%. Two persons who had only indirect contact with the camp developed the disease. Vaccination early in the course of such an outbreak appears to be a useful and practical method of limiting symptomatic infection but not acquisition of the epidemic strain.

Antibody responses to serogroup B meningococcal outer membrane antigens after vaccination and infection

Antibody responses of adult volunteers given a vaccine containing meningococcal capsular polysaccharides (serogroups A, C, Y, and W-135) noncovalently complexed with serotype 2b:P1.2 and 15:P1.16 outer membrane proteins have been studied. Sera were analyzed by enzyme-linked immunosorbent assay methods for immunoglobulin G (IgG), IgM, and IgA antibodies and for bactericidal activities against the homologous strains. The vaccination was performed as a double-blind experiment with 47 volunteers, of whom 23 received the protein-polysaccharide vaccine and 24 received the control preparation containing the polysaccharides only. Ten additional persons volunteered for the protein-polysaccharide vaccine. Before vaccination, carriers of meningococci had significantly higher levels of specific IgG and IgA and also higher bactericidal activities than noncarriers. At 2 weeks postvaccination we found significant IgG and bactericidal antibody responses against both the 2b:P1.2 and 15:P1.16 strains in about 70% of the protein-polysaccharide vaccinees. The immune response induced by disease was compared with that induced by vaccination by analyzing paired sera from 13 survivors of serogroup B serotype 15 meningococcal disease. We found that the mean specific IgG level in acute-phase sera was lower than average in prevaccination sera from the vaccinees but similar to that of healthy noncarriers before vaccination. The convalescent-phase sera showed IgG responses similar to those of the vaccinees, but the IgM response to disease was significantly higher than after vaccination. The immune response to disease caused by serogroup B serotype 15 meningococci was found by enzyme-linked immunosorbent assay analysis to be about the same with outer-membrane antigens from a serotype 2b strain as it was with antigens from a serotype 15 strain.

Appearance of new strains associated with group B meningococcal disease and their use for rapid vaccine development

There has been a decrease in the prevalence of disease in the United States due to meningococcal serotypes 2a and 2b containing class 2 proteins with a concomitant increase in nonserotypable strains containing class 3 major outer membrane proteins. A new disease associated strain was identified using monoclonal antibodies as B:4:P1.15. Serotype 4 strains have been heretofore isolated almost only from carriers. This B:4:P1.15 strain predominated among group B disease isolates in Cuba from the late 1970s to the present and among Miami, Florida isolates recovered in 1981 and 1982. To determine whether protein vaccines for new strains or serotypes could be prepared using our present methods, a combined vaccine was prepared from a group B strain (B:8:P1.15) recovered during a recent outbreak in Virginia, and a serotype 2b strain, plus group C polysaccharide. The vaccine was prepared with aluminum hydroxide, or with trehalose dimycolate plus monophosphoryl lipid A, or without adjuvant. Four weeks after immunization antibody levels were much higher in mice that received vaccine containing adjuvant.

Comparison of meningococcal outer membrane protein vaccines solubilized with detergent or C polysaccharide

Outer membrane proteins (OMPs) were isolated from meningococcal strain H44/76 (B:15:P1.16) by detergent extraction of bacteria. A final product containing class 1 (P1.16), 3(15), 4 OMPs and 5% (w/w) lipooligosaccharide was obtained. Two experimental vaccines were prepared: OMP-detergent and OMP-C polysaccharide. The OMP-detergent vaccine tended to show a better bactericidal: ELISA ratio for the antibodies induced as compared to the OMP-C polysaccharide vaccine. The vaccine induced bactericidal antibodies appeared for the greater part to be directed against the class 1 OMP (P1.16). By comparison of cultures grown in Mueller Hinton Broth with and without 0.25% (w/v) glucose, it was found that monoclonal antibodies against the serotype OMP (class 2 or 3) were not bactericidal against meningococci grown in MHB without glucose. Antibodies against class 1 OMP and lipooligosaccharide were not influenced by this. A new major outer membrane protein (appr. 40 kd) is described that may function as a cation-specific porin.

Protective efficacy of monoclonal antibodies to class 1 and class 3 outer membrane proteins of Neisseria meningitidis B:15:P1.16 in infant rat infection model: new prospects for vaccine development

The protective efficacy of monoclonal antibodies to class 1 and class 3 outer membrane proteins of Neisseria meningitidis B:15:P1.16 was tested in an infant rat infection model. Four monoclonal antibodies to class 1 protein had bactericidal titres exceeding 20,000 and they protected infant rats completely against bacterial challenge with meningococci carrying the same class 1 protein, P1.16. One monoclonal antibody to class 3 protein was highly bactericidal (titer greater than 20,000), whereas two others had no bactericidal activity. All these antibodies gave some protection from infection, resulting in mortalities varying from 66 to 83% as compared to 100% in control rats who had received either unrelated monoclonal antibody or saline. These results strongly speak for class 1 outer membrane protein as a vaccine candidate for meningococcus group B.

Human immunoglobulin G subclass immune response to outer membrane antigens in meningococcal group B vaccine

The immunoglobulin G (IgG) subclass distribution of antibodies against the major outer membrane proteins from serotype 2a Neisseria meningitidis in human vaccinees was studied by immunoblotting. The volunteers received two doses of a noncovalent complex of group B polysaccharide and outer membrane material from the same meningococcal strain. Six weeks after the first vaccination the antibodies mounted against the class 1 and 5 proteins belonged mainly to the IgG1 and IgG3 subclasses. However, the binding of IgG3 to the class 5 proteins decreased markedly in serum samples taken after 25 weeks. Antibody binding to the serotype-specific class 2 protein was dependent on renaturation of the antigen by a dipolar ionic detergent (R. E. Mandrell and W. D. Zollinger, J. Immunol. Methods 67:1-11, 1984). The immune response against this protein showed more individual variation and consisted of IgG1 or IgG3 or both, often combined with IgG4.

Immunologic priming to capsular polysaccharide in infants immunized with Haemophilus influenzae type b polysaccharide-Neisseria meningitidis outer membrane protein conjugate vaccine

Thirty children vaccinated at 2 to 17 months of age with Haemophilus influenzae type b polysaccharide linked to a partially purified 40,000 dalton outer membrane protein of Neisseria meningitidis were revaccinated 10 to 14 months later with conventional H. influenzae type b polysaccharide vaccine. The geometric mean anti-type b antibody concentration before reimmunization was 0.68 micrograms/mL, and rose to 31 micrograms/mL in sera obtained 1 month later. The mean level after immunization was not significantly different than that in sera from 12 adults immunized with type b polysaccharide vaccine (51 micrograms/mL, P = 0.3), and was 10-fold higher than that of 13 control children immunized with type b polysaccharide for the first time (2.7 micrograms/mL, P less than 0.001). The IgG responses of the children first given conjugate vaccine and then conventional type b polysaccharide vaccine were of a similar magnitude as those in the immunized adults. Further, the children maintained high levels of serum antibody 6 to 8 months later. Ten other children vaccinated in infancy with conjugate vaccine, and again with conjugate vaccine 10 to 15 months later, showed similar antibody responses to those of the group given conjugate vaccine in infancy, and booster with conventional polysaccharide vaccine. Thus vaccination with H. influenzae type b polysaccharide-outer membrane protein conjugate vaccine primes the immune system to an IgG memory antibody response to either type b polysaccharide or conjugate vaccine. Post-booster sera from all children tested showed high titers of functional activity in a complement-mediated bactericidal assay. These data suggest that protection of most infants from type b Haemophilus disease may be achieved by a combination of immunization at 2 to 4 months of age with this conjugate vaccine, and reimmunization 1 year later with conjugate or conventional type b polysaccharide vaccine.

An integrated molecular and immunological approach towards a meningococcal group B vaccine

There has been a notable lack of success in producing an effective vaccine against Neisseria meningitidis group B infections, despite such prophylaxis being available for group A and C disease. The reasons for this are reviewed and evidence presented that a vaccine based on the group B capsular polysaccharide should be pursued. To be effective, a clear understanding of, and improvement in the poor immunogenicity of the polysaccharide is required. Consequently, the nature of the antigenic structure involved in immune recognition has been evaluated at the molecular level and reasons for the poor immunogenicity of the B polysaccharide are presented. Methods of increasing the immunogenicity are proposed with the intention of undertaking human volunteer trials.

Prospects for the prevention of meningococcal disease: special reference to group B

Safe and effective polysaccharide (PS) vaccines for prevention of bacteraemia and meningitis due to meningococcal serogroups A, C, Y, and W135 have been licensed for a number of years in the United States and in some European countries. The bivalent AC and the tetravalent ACYW135 PS vaccines have generally been used in the civilian population only for the control of outbreaks. A major meningococcal disease problem persists in parts of Africa, especially in the so-called 'meningitis belt'. Studies by Greenwood and Wali have shown that a cost effective way to control the disease in Africa is to vaccinate the entire population of a village at the start of an outbreak. When this was done they found that further cases of group A disease ceased within ten days. There are, however, some problems with the existing PS vaccines. The group C PS is less immunogenic in young children than the three other PS, and does not protect children below 18 to 24 months of age. This problem will probably be solved by conjugation of the group C PS to a protein carrier, analogous to that which has been done with the Haemophilus influenzae type b PS.

Control of epidemic group A meningococcal meningitis in Nepal

During the first six months of 1983, an epidemic of serogroup A meningococcal meningitis occurred in the Kathmandu valley of Nepal, resulting in 875 cases and 95 deaths. The annual attack rate was 103 cases per 100,000 population, with a peak attack rate occurring in April. Epidemic meningococcal disease had not been recognized previously in Nepal. Early in 1984, a review of hospital-based data on pyogenic meningitis in Kathmandu showed three times as many cases per month compared with the same period the previous year, suggesting that a recurrent epidemic was unfolding. Beginning in February 1984, a vaccination campaign directed at a high-risk target population of people aged 1-24 years was launched; over 329,000 doses of bivalent A/C meningococcal vaccine were given, achieving approximately 64% coverage of the target population. A dramatic decline in the number of new meningitis cases occurred coincident with the initiation of the mass vaccination campaign. This experience demonstrates that it is possible, with appropriate surveillance efforts, to detect an evolving epidemic of meningococcal disease early in its course and to institute control measures in advance of the expected epidemic peak.

Human bactericidal antibody response to meningococcal outer membrane protein vaccines

Several different meningococcal outer membrane protein vaccines have been prepared and used in human safety and immunogenicity studies. The results of these studies have led to some general conclusions regarding the human antibody response to these vaccines. A review of these conclusions, however, indicates that a number of important questions and problems still need to be addressed. Two of these are the determination of the protective level of bactericidal antibody in human serum and the impact of phase variation of surface antigens on vaccine strategy. Bactericidal assays using intrinsic complement and high concentrations of serum suggest that the level of natural immunity to group B meningococci is quite high, but is increased by vaccination with outer membrane protein vaccine. Phase variation in meningococcal surface antigens including capsule, class 1 protein, class 5 protein, and lipopolysaccharide was demonstrated using colony blotting with monoclonal antibodies. Phase variation resulted in differences in susceptibility to the bactericidal activity of human sera.

Humoral antibody responses to biannual multiantigen vaccination: report of a field trial on children in Sudan

One hundred and sixty-six children aged 3-30/12 were enrolled in this study. Initially all children were given a single injection containing live measles vaccine, diphtheria and tetanus toxoids, inactivated polio vaccine and meningococcal, A & C polysaccharide, plus an intradermal injection of BCG. In a second visit 6 months later each child was tuberculin tested and given a second dose of all the above vaccines with the exception of BCG. Blood samples were obtained before and 1 month after each vaccination. Following the second dose there was satisfactory seroconversion for all the vaccines. Tuberculin positivity rose from 5.4% before BCG vaccination to 94.4% 6 months after its administration. It is concluded that it is safe and effective to give these antigens simultaneously and that this particular schedule lends itself for use with nomadic and other unaccessible groups of population.

Use of bacterial vaccines for prevention of pneumococcal and meningococcal disease in the day care setting

The pneumococcus causes severe disease, including meningitis and bacteremia, in children of day care age. It is also a frequent cause of otitis media. Unfortunately, the currently available pneumococcal polysaccharide vaccine has not been efficacious in children under 24 months old; research is currently underway on methods for increasing immunogenicity in young children. The meningococcus is a rare cause of meningitis in day care aged children, but children in day care are likely to be at increased risk of secondary disease if a case occurs in a center. The currently available polysaccharide meningococcal vaccine is poorly immunogenic in children younger than two and does not include the group B polysaccharide, which is responsible for 70% of disease in children younger than five years. Therefore, chemoprophylaxis with rifampin is recommended for decreasing the risk of secondary spread. When a group B meningococcal vaccine immunogenic in young children becomes available, vaccination will be indicated for all children in day care.

Human antibody response to a group B serotype 2a meningococcal vaccine determined by immunoblotting

The antibody response of 30 volunteers vaccinated with a complex of group B polysaccharide and outer membrane vesicles (OMV) from serotype 2a Neisseria meningitidis and of 3 individuals who received a placebo vaccine was determined by immunoblotting. OMV were separated by sodium dodecyl sulfate-gel electrophoresis and electrotransferred to nitrocellulose filters. Binding of immunoglobulin G (IgG), IgA, and IgM antibodies in the human sera to OMV components was detected with class-specific peroxidase-conjugated antibodies. The immunoblotting results were also related to the bactericidal activity of the sera and the meningococcal carrier status of the volunteers. Before vaccination weakly reactive bands in the molecular weight range of 140,000 to 10,000 were observed on the blots. Sera from carriers showed more marked bands. Individual patterns of increased reactivity were seen 6 weeks after vaccination. The main immunoreactive components of OMV corresponded to a molecular weight of 43,000 (class 1 protein), 30,000 (class 5 proteins), and 22,000. IgG antibodies in postvaccination sera of high bactericidal titers showed distinct binding to the 43,000-molecular-weight antigen. Meningococcal carriers had antibodies against an antigen of 22,000 molecular weight; in polyacrylamide gels this component did not stain with Coomassie brilliant blue or silver. The marked binding of IgG antibodies to the class 5 proteins decreased considerably between weeks 6 and 25 after vaccination. Periodate oxidation of OMV abolished the binding of IgG antibodies to the class 5 proteins, whereas the antigenicity of the 43,000-molecular-weight (class 1 protein) and 22,000-molecular-weight antigens was unaffected.