Paul M. Mendelman

The Efficacy of Live Attenuated, Cold-Adapted, Trivalent, Intranasal Influenzavirus Vaccine in Children

BACKGROUND Influenzavirus vaccine is used infrequently in healthy children, even though the rates of influenza in this group are high. We conducted a multicenter, double-blind, placebo-controlled trial of a live attenuated, cold-adapted, trivalent influenzavirus vaccine in children 15 to 71 months old. METHODS Two hundred eighty-eight children were assigned to receive one dose of vaccine or placebo given by intranasal spray, and 1314 were assigned to receive two doses approximately 60 days apart. The strains included in the vaccine were antigenically equivalent to those in the inactivated influenzavirus vaccine in use at the time. The subjects were monitored with viral cultures for influenza during the subsequent influenza season. A case of influenza was defined as an illness associated with the isolation of wild-type influenzavirus from respiratory secretions. RESULTS The intranasal vaccine was accepted and well tolerated. Among children who were initially seronegative, antibody titers increased by a factor of four in 61 to 96 percent, depending on the influenza strain. Culture-positive influenza was significantly less common in the vaccine group (14 cases among 1070 subjects) than the placebo group (95 cases among 532 subjects). The vaccine efficacy was 93 percent (95 percent confidence interval, 88 to 96 percent) against culture-confirmed influenza. Both the one-dose regimen (89 percent efficacy) and the two-dose regimen (94 percent efficacy) were efficacious, and the vaccine was efficacious against both strains of influenza circulating in 1996-1997, A(H3N2) and B. The vaccinated children had significantly fewer febrile illnesses, including 30 percent fewer episodes of febrile otitis media (95 percent confidence interval, 18 to 45 percent; P<0.001). CONCLUSIONS A live attenuated, cold-adapted influenzavirus vaccine was safe, immunogenic, and effective against influenza A(H3N2) and B in healthy children.

Efficacy of vaccination with live attenuated, cold-adapted, trivalent, intranasal influenza virus vaccine against a variant (A/Sydney) not contained in the vaccine

OBJECTIVE To determine the safety, immunogenicity, and efficacy of revaccination of children with live attenuated influenza vaccine. STUDY DESIGN A 2-year multicenter, double-blind, placebo-controlled, efficacy field trial of live attenuated, cold-adapted trivalent influenza vaccine administered by nasal spray to children. This report summarizes year 2 results, a year in which the epidemic strain of influenza A/Sydney was not well matched to the vaccine strains. Each year, vaccine strains were antigenically equivalent to the contemporary inactivated influenza vaccine. In year 2, a single intranasal revaccination was administered. Active surveillance for influenza was conducted during the influenza season by means of viral cultures. Influenza cases were defined as illnesses with wild-type influenza virus isolated from respiratory secretions. RESULTS In year 2, 1358 (85%) children, 26 to 85 months of age, returned for revaccination. The intranasal vaccine was easily accepted, well tolerated, and immunogenic. Revaccination resulted in 82% to 100% of the vaccinated children in a subset studied for immunogenicity being seropositive as compared with 26% to 65% of placebo recipients, depending on the influenza strain tested. No serious adverse events were associated with the vaccine. In addition to the strains in the vaccine, antibody was induced to the variant strain A/Sydney/H3N2. In year 2, influenza A/Sydney/H3N2, a variant not contained in the vaccine, caused 66 of 70 cases of influenza A; nonetheless, intranasal vaccine was 86% efficacious in preventing A/Sydney influenza. Eight cases of lower respiratory tract disease were associated with A/Sydney influenza; all cases were in the placebo group. CONCLUSIONS This live attenuated, cold-adapted influenza vaccine was safe, immunogenic, and efficacious against influenza A/H3N2 (including a variant, A/Sydney, not contained in the vaccine) and influenza B. The characteristics of this vaccine make it suitable for routine use in children to prevent influenza.

Correlates of Immune Protection Induced by Live, Attenuated, Cold-Adapted, Trivalent, Intranasal Influenza Virus Vaccine

The authors conducted a 2-year, multicenter, double-blind, placebo-controlled efficacy field trial of live, attenuated, cold-adapted, trivalent influenza vaccine administered by nasal spray to children 15-71 months old. Overall, vaccine was 92% efficacious at preventing culture-confirmed infection by influenza A/H3N2 and influenza B. Because influenza A/H1N1 did not cause disease during the years in which this study was conducted, the authors sought to determine vaccine efficacy and correlates of immune protection against experimental challenge with 107 TCID50 of attenuated H1N1 (vaccine strain) by intranasal spray. Prechallenge assessments included serum hemaglutination-inhibiting (HAI) antibody and nasal wash IgA antibody to H1N1. Vaccine was 83% efficacious (95% confidence interval, 60%-93%) at preventing shedding of H1N1 virus after challenge. Any serum HAI antibody or any nasal wash IgA antibody was correlated with significant protection from H1N1 infection as indicated by vaccine-virus shedding, and high efficacy against H1N1 challenge was demonstrated.

Norovirus Vaccine against Experimental Human Norwalk Virus Illness

BACKGROUND Noroviruses cause epidemic and sporadic acute gastroenteritis. No vaccine is available to prevent norovirus illness or infection. METHODS We conducted a randomized, double-blind, placebo-controlled, multicenter trial to assess the safety, immunogenicity, and efficacy of an investigational, intranasally delivered norovirus viruslike particle (VLP) vaccine (with chitosan and monophosphoryl lipid A as adjuvants) to prevent acute viral gastroenteritis after challenge with a homologous viral strain, Norwalk virus (genotype GI.1). Healthy adults 18 to 50 years of age received two doses of either vaccine or placebo and were subsequently inoculated with Norwalk virus and monitored for infection and gastroenteritis symptoms. RESULTS Ninety-eight persons were enrolled and randomly assigned to receive vaccine (50 participants) or placebo (48 participants), and 90 received both doses (47 participants in the vaccine group and 43 in the placebo group). The most commonly reported symptoms after vaccination were nasal stuffiness, nasal discharge, and sneezing. Adverse events occurred with similar frequency among vaccine and placebo recipients. A Norwalk virus-specific IgA seroresponse (defined as an increase by a factor of 4 in serum antibody levels) was detected in 70% of vaccine recipients. Seventy-seven of 84 participants inoculated with Norwalk virus were included in the per-protocol analysis. Vaccination significantly reduced the frequencies of Norwalk virus gastroenteritis (occurring in 69% of placebo recipients vs. 37% of vaccine recipients, P=0.006) and Norwalk virus infection (82% of placebo recipients vs. 61% of vaccine recipients, P=0.05). CONCLUSIONS This norovirus VLP vaccine provides protection against illness and infection after challenge with a homologous virus. (Funded by LigoCyte Pharmaceuticals and the National Institutes of Health; ClinicalTrials.gov number, NCT00973284.).

Bacteriology of acute otitis media: a new perspective.

Pathogenic bacteria were isolated from 90% of patients with acute otitis media. This higher-than-expected rate of positive cultures was probably related to the meticulous bacteriologic techniques used.

Adjuvanted Intranasal Norwalk Virus-Like Particle Vaccine Elicits Antibodies and Antibody-Secreting Cells That Express Homing Receptors for Mucosal and Peripheral Lymphoid Tissues

BACKGROUND Noroviruses cause significant morbidity and mortality from acute gastroenteritis in all age groups worldwide. METHODS We conducted 2 phase 1 double-blind, controlled studies of a virus-like particle (VLP) vaccine derived from norovirus GI.1 genotype adjuvanted with monophosphoryl lipid A (MPL) and the mucoadherent chitosan. Healthy subjects 18-49 years of age were randomized to 2 doses of intranasal Norwalk VLP vaccine or controls 21 days apart. Study 1 evaluated 5-, 15-, and 50-μg dosages of Norwalk antigen, and study 2 evaluated 50- and 100-μg dosages. Volunteers recorded symptoms for 7 days after dosing, and safety was followed up for 180 days. Blood samples were collected for serological profile, antibody secreting cells (ASCs), and analysis of ASC homing receptors. RESULTS The most common symptoms were nasal stuffiness, discharge, and sneezing. No vaccine-related serious adverse events occurred. Norwalk VLP-specific immunoglobulin G and immunoglobulin A antibodies increased 4.8- and 9.1-fold, respectively, for the 100-μg dosage level. All subjects tested who received the 50- or 100-μg vaccine dose developed immunoglobulin A ASCs. These cells expressed molecules associated with homing to mucosal and peripheral lymphoid tissues. CONCLUSIONS The intranasal monovalent adjuvanted Norwalk VLP vaccine was well tolerated and highly immunogenic and is a candidate for additional study.

Immunogenicity of heptavalent pneumococcal conjugate vaccine in infants.

OBJECTIVE To evaluate the safety, immunogenicity, and immunologic memory in young infants of a seven-valent (6B, 14, 19F, 23F, 18C, 4, 9V) pneumococcal vaccine conjugated to the outer membrane protein complex of Neisseria meningitidis. VACCINEES: Healthy 2-month-old infants 12- to 15-month-old control infants were recruited from participating private practices. METHODS Infants (n = 25) were vaccinated at 2, 4, and 6 months of age with the conjugated pneumococcal vaccine, followed by a single dose of licensed pneumococcal polysaccharide vaccine (n = 20) at 12 to 15 months of age. Thirteen infants who had not received the investigational pneumococcal conjugate vaccine served as control subjects and were given a single dose of the licensed pneumococcal polysaccharide vaccine at 12 to 15 months of age. RESULTS The investigational pneumococcal conjugate vaccine was well tolerated by infants. The vaccine was highly immunogenic in young infants, with significant increases in antibody to all seven serotypes after either two or three injections. At 12 to 15 months of age, infants who had been primed with the investigational pneumococcal conjugate vaccine had a brisk immunologic response to the booster injection of the licensed pneumococcal polysaccharide vaccine. Control infants, who received a single primary injection of the licensed pneumococcal polysaccharide vaccine, had negligible immunologic responses to four of the seven serotypes and low responses to the other three types. CONCLUSION The investigational seven-valent pneumococcal conjugate vaccine administered to young infants was well tolerated and highly immunogenic and provided immunologic memory to an injection of the licensed pneumococcal polysaccharide vaccine.

Characterization of non-beta-lactamase-mediated ampicillin resistance in Haemophilus influenzae.

Ampicillin resistance in Haemophilus influenzae is most often due to the plasmid-mediated production of TEM beta-lactamase. We studied four strains with high-level ampicillin resistance (MIC of 32 micrograms/ml with an inoculum of 10(5) CFU on solid media) which did not produce detectable beta-lactamase activity with two different detection methods. Two of the four strains contained extrachromosomal DNA by agarose gel electrophoresis. Conjugation failed to transfer ampicillin resistance; in contrast, transformation yielded ampicillin-resistant transformants in three of the four strains. These transformants did not contain detectable extrachromosomal DNA. In addition, mobilization of the resistance determinant by transformation to, or conjugation with, recombination-deficient strains was unsuccessful. DNA-DNA hybridization experiments revealed no homology of the DNA of these strains with two R plasmids (one coding for ampicillin resistance, the other for chloramphenicol and tetracycline resistance). We conclude that the genetic basis of the non-beta-lactamase ampicillin resistance in these strains appears to be chromosomally mediated. We investigated the mechanism of resistance in these strains. Enzymatic modification of penicillin was not detected by autoradiography of a thin-layer chromatogram of cell sonic extracts of three ampicillin-resistant transformant strains incubated with [14C]penicillin. To assess changes in permeability of the cell envelope, a plasmid coding for beta-lactamase was conjugated into these strains, and the hydrolysis of penicillin by intact cells and cell sonic extracts was compared. Only one of three transformant strains had significantly diminished permeability. Outer membrane proteins of these strains analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed apparent differences in comparison with the isogenic ampicillin-susceptible recipient strain. Autofluorography of a sodium dodecyl sulfate-polyacrylamide gel electrophoresis of Sarkosyl-solubilized crude membrane (the putative inner membranes) from these ampicillin-resistant transformant strains incubated with [3H]penicillin compared with the isogenic ampicillin-susceptible recipient strain revealed reduced binding to PBP 3 and 6, 3 and 4, or 4. In addition, affinity binding studies revealed decreased affinity of PBP 4 for ampicillin of all four transformants tested. We conclude that the major mechanism of resistance in these strains is altered penicillin-binding proteins; however, other mechanisms, including permeability, may also play a role. Images

Safety of cold-adapted live attenuated influenza vaccine in a large cohort of children and adolescents

Objective. To determine the safety of cold-adapted trivalent intranasal influenza virus vaccine (CAIV) in children and adolescents. Study design. A randomized, double blind, placebo-controlled safety trial in healthy children age 12 months to 17 years given CAIV (FluMist; MedImmune Vaccines, Inc.) or placebo (randomization, 2:1). Children <9 years of age received a second dose of CAIV or placebo 28 to 42 days after the first dose. Enrolled children were then followed for 42 days after each vaccination for all medically attended events. Prespecified outcomes included 4 prespecified diagnostic groups and 170 observed individual diagnostic categories. The relative risk and the 2-sided 90% confidence interval were calculated for each diagnostic group and individual category by clinical setting, dose and age. More than 1500 relative risk analyses were performed. Results. A total of 9689 evaluable children were enrolled in the study. Of the 4 prespecified diagnostic categories (acute respiratory tract events, systemic bacterial infection, acute gastrointestinal tract events and rare events potentially associated with wild-type influenza), none was associated with vaccine. Of the biologically plausible individual diagnostic categories, 3, acute gastrointestinal events, acute respiratory events and abdominal pain, had different analyses that demonstrated increased and decreased relative risks, making their association with the vaccine unlikely. For reactive airway disease a significant increased relative risk was observed in children 18 to 35 months of age with a relative risk of 4.06 (90% confidence interval, 1.29 to 17.86) in this age group. The individual diagnostic categories of upper respiratory infection, musculoskeletal pain, otitis media with effusion and adenitis/adenopathy had at least one analysis that achieved a significant increased risk ratio. All of these events were infrequent. Conclusion. CAIV was generally safe in children and adolescents. The observation of an increased risk of asthma/reactive airway disease in children <36 months of age is of potential concern. Further studies are planned to evaluate the risk of asthma/reactive airway disease after vaccine.

Cost benefit of influenza vaccination in healthy, working adults: An economic analysis based on the results of a clinical trial of trivalent live attenuated influenza virus vaccine

INTRODUCTION Trivalent, intranasal, live attenuated influenza virus vaccine (LAIV) is safe and clinically effective in healthy, working adults. However, the potential economic benefits of vaccinating this population are still uncertain. We therefore conducted a cost benefit analysis of influenza vaccination of healthy working adults utilizing clinical outcome data from a trial of LAIV in healthy working adults. METHODS This cost benefit analysis was based on the results of a multi-center, randomized, double blind placebo controlled trial that assessed the clinical effectiveness of LAIV in healthy working adults. Outcomes from the trial that were included in the cost benefit analysis were days of work missed, days working but at reduced effectiveness, and days with a health care provider visit due to at least one of the following symptoms: fever, runny nose, sore throat, cough, headache, muscle aches, chills, or tiredness/weakness. Cost data were obtained from nationally representative databases. Probability distributions for the key model variables were defined, and Monte Carlo simulation was used to estimate the mean break even costs for vaccine and its administration. Sensitivity analyses explored how changes in the variables affected these estimates. RESULTS There were 4561 participants in the clinical trial. LAIV lowered work loss due to illness symptoms by 18% (relative rate [RR] 0.82, 95% confidence interval [CI] 0.74-0.91), days of working at reduced effectiveness by 18% (RR 0.82, 95% CI 0.74-0.91), and days with a health care provider visit by 13% (RR 0.87, 95% CI 0.77-0.98). The mean break even cost for vaccine and its administration was 43.07 US dollars per person vaccinated (5-95% percentiles, 25.72-58.92 US dollars). Major cost drivers were hourly wage and vaccine effectiveness in reducing productivity losses and health care use. CONCLUSION This cost benefit analysis based on the results of the LAIV trial provides additional evidence that influenza vaccination may provide both health and economic benefits for healthy, working adults.