Live attenuated influenza A virus vaccines in children: results of a field trial

Clinical endpoints to inform vaccine policy: A systematic review of outcome measures from pediatric influenza vaccine efficacy trials

INTRODUCTION

We conducted a systematic review of pediatric influenza vaccine efficacy trials to assess clinical outcome measures and whether the trials defined important public health endpoints.

MATERIAL AND METHODS

We systematically identified phase 3 or 4 influenza vaccine randomized controlled trials among children ≤18 years of age with laboratory-confirmed influenza outcomes since 1980. We recorded countries, age groups, vaccine formulations, specimen collection criteria, laboratory diagnostics, primary and secondary outcome measures, and funders, and we determined income category for study countries. We used descriptive statistics to summarize study characteristics. We analyzed the studies overall and a subset of studies conducted in at least one low- and middle-income country (LMIC).

RESULTS

From 6455 potentially relevant articles, we identified 41 eligible studies. Twenty-one studies (51%) were conducted in at least one LMIC, while the remaining studies (49%) were conducted in high-income countries only. Thirty-one studies (76%) included children younger than six years. We found 40 different primary outcome measures among the 41 eligible studies. Thirty-three studies (80%) reported standardized symptoms or findings which defined a primary outcome or triggered specimen collection. One study defined a primary outcome which captured more severe illness; however, cases were mostly due to high body temperature without other severity criteria. Of the 21 studies from at least one LMIC, 15 (71%) were published since 2010 and 17 (81%) enrolled children younger than six years. Eighteen (86%) studies from at least one LMIC reported standardized symptoms or findings which defined a primary outcome or triggered specimen collection.

CONCLUSIONS

Among pediatric influenza vaccine efficacy trials, primary outcome measures and clinical specimen collection criteria were highly variable and, with one exception, focused on capturing any influenza illness. As most LMICs do not have influenza vaccination programs, our study highlights a potential data limitation affecting policy and implementation decisions in these settings.

Evaluation of influenza A and B cold-adapted reassortant virus reproduction in trivalent live influenza vaccines

BACKGROUND

The objective of the present study was to compare reproduction of trivalent LAIV vaccine strains in MDCK cells and to perform quantitative RT-PCR analysis of trivalent LAIV replication after inoculation in mice.

METHODS

We applied a reverse transcriptase real-time PCR (rRT-PCR) analysis using TaqMan technique to evaluate the infectious titers of vaccine strains containing in trivalent live influenza vaccines (LAIVs). We confirmed the PCR data in ELISA using staining of MDCK monolayer with mouse monoclonal antibodies to hemagglutinin.

RESULTS

The viral load during the reproduction of mono-vaccines and trivalent LAIV in MDCK cells was similar at low dilutions. The content of vaccine viruses was evaluated using quantitative RT-PCR analysis in the nasal turbinate and lungs of CBA mice on day 3 after intranasal immunization. It was shown that despite the almost complete absence of reproduction of the A/H3N2 virus in mice, the immune response of A/H3N2-specific antibodies was formed at the same level as to other viruses. In MDCK cells, a decreased infectious titers of vaccine viruses in trivalent LAIV compared to mono-vaccines was demonstrated except for B/Yamagata virus.

CONCLUSION

RT-PCR analysis is applicable to assess the growth characteristics of cold-adapted reassortant influenza viruses in vitro and in mice. The interference of trivalent LAIV vaccine viruses in MDCK cells was minimal at low dilutions. In mice, decrease in infectious titers did not lead to a decline of the immunogenicity.

Functional immune response to influenza H1N1 in children and adults after live attenuated influenza virus vaccination

Influenza virus is a major respiratory pathogen, and vaccination is the main method of prophylaxis. In 2012, the trivalent live attenuated influenza vaccine (LAIV) was licensed in Europe for use in children. Vaccine-induced antibodies directed against the main viral surface glycoproteins, haemagglutinin (HA) and neuraminidase (NA) play important roles in limiting virus infection. The objective of this study was to dissect the influenza-specific antibody responses in children and adults, and T cell responses in children induced after LAIV immunization to the A/H1N1 virus. Blood samples were collected pre- and at 28 and 56 days post-vaccination from 20 children and 20 adults. No increase in micro-neutralization (MN) antibodies against A/H1N1 was observed after vaccination. A/H1N1 stalk-specific neutralizing and NA-inhibiting (NI) antibodies were boosted in children after LAIV. Interferon γ-producing T cells increased significantly in children, and antibody-dependent cellular-mediated cytotoxic (ADCC) cell activity increased slightly in children after vaccination, although this change was not significant. The results indicate that the NI assay is more sensitive to qualitative changes in serum antibodies after LAIV. There was a considerable difference in the immune response in children and adults after vaccination, which may be related to priming and previous influenza history. Our findings warrant further studies for evaluating LAIV vaccination immunogenicity.

Live attenuated influenza virus vaccines by computer-aided rational design

Influenza claims 250,000 - 500,000 lives annually worldwide. Despite existing vaccines and enormous efforts in biomedical research, these staggering numbers have not changed significantly over the last two decades1, motivating the search for new, more effective, vaccines that can be rapidly designed and easily produced. Using influenza virus strain A/PR/8/34, we describe a systematic, rational approach, termed Synthetic Attenuated Virus Engineering (SAVE), to develop new, efficacious live attenuated influenza virus vaccine candidates through genome-scale changes in codon pair bias. Attenuation is based on many hundreds of nucleotide changes across the viral genome, offering high genetic stability and a wide margin of safety. The method can be applied rapidly to any emerging influenza virus in its entirety, an advantage that is significant for dealing with seasonal epidemics and pandemic threats, such as H5N1- or 2009-H1N1 influenza.

Technical report: Reduction of the influenza burden in children

Epidemiologic studies have shown that children of all ages with certain chronic conditions, such as asthma, and otherwise healthy children younger than 24 months (6 through 23 months) are hospitalized for influenza and its complications at high rates similar to those experienced by the elderly. Annual influenza immunization is already recommended for all children 6 months and older with high-risk conditions. By contrast, influenza immunization has not been recommended for healthy young children. To protect children against the complications of influenza, increased efforts are needed to identify and recall high-risk children. In addition, immunization of children between 6 through 23 months of age and their close contacts is now encouraged to the extent feasible. Children younger than 6 months may be protected by immunization of their household contacts and out-of-home caregivers. The ultimate goal is universal immunization of children 6 to 24 months of age. Issues that need to be addressed before institution of routine immunization of healthy young children include education of physicians and parents about the morbidity caused by influenza, adequate vaccine supply, and appropriate reimbursement of practitioners for influenza immunization. This report contains a summary of the influenza virus, protective immunity, disease burden in children, diagnosis, vaccines, and antiviral agents.

Universal vaccination of healthy children against influenza: a role for the cold-adapted intranasal influenza vaccine

The incidence of influenza in children well exceeds that of the elderly and has been identified as the basis for 20% of doctor visits for children during the winter. The disease results in over 100 hospitalizations per 100000 person-months in children <2 years of age. Furthermore, children serve as the major vector in the community; thus, influenza in children results in significant costs to society. Although efficacious, the current intramuscular, inactivated influenza vaccine is infrequently used in children, and is currently targeted only at children at high risk and those who are household members of such individuals. Experts believe that vaccinating only high risk individuals has little impact on the cycle of annual epidemics, but that universal vaccination of children may very well have a substantial impact. Experimental data support this. A recently published cost-benefit analysis indicated that routine, school-aged vaccination through individual visits to a clinician would save 4 US dollars per child vaccinated. A group program such as a school-based one would save 35 US dollars. One obstacle to universal vaccination includes the real and perceived resistance to the addition of yet another annual injection to the already crowded schedule of routine childhood immunizations. Nearing licensure is an intranasal, live attenuated, cold-adapted intranasal influenza vaccine. Cold-adaptation prevents replication in the lower respiratory tract. Trials have demonstrated immunogenicity, safety, and tolerability in adults as well as children. Placebo-controlled trials have shown efficacy rates of 83 to 94%. This novel vaccine addresses obstacles to universal childhood immunization and would permit a program of routine use that would dramatically reduce transmission and stem epidemics of influenza.

The role of live influenza vaccines in children

Live attenuated cold-adapted influenza vaccines (CAIVs) have been developed over the past two decades by taking advantage of the segmented RNA genome of influenza and creating attenuated reassortants containing contemporary hemagglutinin (HA) and neuraminidase (NA) genes. These vaccines have been shown to be easily administered, safe and immunogenic in adults and children. Recent trials of a trivalent live attenuated CAIV (CAIV-T, tradename FluMist, Aviron, Mt. View, CA) in children have demonstrated greater than 85% efficacy against culture positive H3N2 and B influenza illness and complications, such as otitis media. CAIV-T also prevented shedding of H1N1 virus in 83% of vaccinated subjects after a monovalent CAIV challenge. Nasal IgA and serum HA inhibition (HAI) antibody produced by these vaccines have been associated with protection against infection, but protection may exist even in the absence of identifiable antibody response. Work to date documenting phenotypic and genetic stability, low likelihood of reactogenicity, infrequent transmissibility and attenuating properties of reassortants heralds promise for the broad use of this vaccine. Targeting children to receive this vaccine may now prove practical and may serve to reduce overall influenza morbidity, given the significant contribution of the pediatric age group of children to influenza illness burden and community spread. Studies of vaccine use in community settings will aid in determining the public health future of this approach.

Safety of the trivalent, cold-adapted influenza vaccine (CAIV-T) in children

The trivalent, cold-adapted influenza vaccine (CAIV-T, FluMist, Aviron, Mountain View, CA) is a live attenuated influenza virus vaccine that is administered by nasal spray. CAIV-T is efficacious in preventing influenza virus infection. The vaccine was submitted to the Food and Drug Administration for licensure in healthy children and adults. Universal immunization is being considered in children, and an effective vaccine with minimal adverse reactions is thus required. The published studies on the safety of CAIV-T in children reviewed in this article were clinical trials sponsored by the National Institutes of Health (NIH) conducted in children from 1975 to 1991, clinical trials from 1991 to 1993 sponsored by a cooperative agreement between NIH and Wyeth-Ayerst Research, and clinical trials from 1995 to the present sponsored by a cooperative agreement between NIH and Aviron. Safety assessments included the occurrence of: 1) specific influenza-like symptoms, unexpected symptoms, and use of medications within the first 10 days after vaccination; 2) acute illness and use of medication within 11 to 42 days postvaccination; 3) serious adverse events and rare events within 42 days after vaccination; 4) healthcare utilization within 14 days after vaccination; and 5) acute respiratory symptoms with annual sequential vaccine doses. CAIV-T was safe and well-tolerated. Transient, mild respiratory symptoms were observed in a minority (10%-15%) of children and primarily with the first CAIV-T dose. Vomiting and abdominal pain occurred in fewer than 2 percent of CAIV-T recipients. The gastrointestinal symptoms were mild and of short duration. An excess of illness or use of medication was not observed after the 10th day of vaccination. Sequential annual doses of CAIV-T were well-tolerated and not associated with increased reactogenicity. CAIV-T did not cause an increase in healthcare utilization. Thus CAIV-T is safe in healthy children and should complement the use of inactivated influenza vaccine, trivalent (IIV-T) in children with underlying chronic conditions.

Live attenuated vaccines against influenza; an historical review

Live attenuated vaccines administered directly to the respiratory tract offer the promise of providing more effective immunity against influenza than subunit or split inactivated vaccines. Evidence has accumulated in recent years that immunological responses relevant to both the prevention of and recovery from influenza are best induced by natural infection. The ease with which the genes of influenza viruses reassort when two or more viruses infect a single cell has been exploited as a means of rapidly producing attenuated vaccines. Donor strains that have been shown by extensive testing to be fully attenuated are used to co-infect cells with contemporary epidemic strains to produce reassortants with the required degree of avirulence and the surface antigens of the epidemic strain. Reassortants prepared from cold-adapted mutants of both influenza A and B viruses have been widely shown from clinical trials in both the United States and Russia over many years to be well tolerated in both adults and children and to be highly efficacious.

Influenza: vaccination and treatment

Few conditions exert such an enormous toll of absenteeism, suffering, medical consultations, hospitalization, death and economic loss as influenza. Patients at high risk of complications and mortality include the elderly and those with pre-existing cardiopulmonary disease. The outbreak in 1997 in Hong Kong, of avian H5N1 influenza in man, which resulted in six deaths among 18 hospitalized cases, and the recent isolation of H9N2 viruses from two children in Hong Kong, are reminders that preparation must be made for the next pandemic. Since the 1970s, efforts to control influenza have mostly focussed on the split product and surface antigen vaccines. These vaccines are of proven efficacy in healthy adults and are effective in elderly people with and without medical conditions putting them at high risk of complications and death following influenza infection. However, vaccine coverage is patchy and often low, and outbreaks of influenza are not uncommon in well-immunized residents of nursing homes. New vaccines and methods of vaccine delivery are being developed in attempts to overcome the limitations of existing vaccines. The antiviral drugs amantadine and rimantadine were developed in the 1960s, but have not been used widely due to their spectrum of activity, rapid emergence of resistance, and adverse effects associated with amantadine. The site of enzyme activity of the influenza neuraminidase is highly conserved between types, subtypes and strains of influenza and has emerged as the target of an exciting new class of antiviral agents that are effective both prophylactically and as therapy.

Safety, efficacy and effectiveness of the influenza virus vaccine, trivalent, types A and B, live, cold-adapted (CAIV-T) in healthy children and healthy adults

Influenza is a major cause of illness. We have assessed the safety, efficacy, and effectiveness of CAIV-T vaccine. A two year, multicenter, double-blind, placebo-controlled, efficacy field trial in pre-school aged children was conducted; 1602 enrolled in Year One and 1358 (85%) returned in Year Two. In both study years combined, the overall vaccine efficacy against culture-confirmed influenza was 92% (95% CI: 88, 94). The vaccine efficacy was 95% (95% CI: 62, 99) against lower respiratory illness, 94% (95% CI: 90, 96) against febrile illness and 96% (95% CI: 88, 99) against otitis media associated with culture-confirmed influenza. A multicenter, double-blind, placebo-controlled, effectiveness field trial was conducted in 4561 working adults aged 18 to 64 years. Episodes and days of febrile illness (FI), severe febrile illness (SFI), febrile upper respiratory illness (FURI), work loss, and health care use were assessed. Vaccination significantly reduced the numbers of SFI, 18.8% reduction (95% CI: 7, 29), and FURI, 26.3% reduction (95% CI: 13, 33); and led to fewer days of illness (22.9% reduction for FI, 27.3% reduction for SFI), fewer days of work lost (17.9% reduction for SFI, 28.4% for FURI), and fewer days of health care provider visits (24.8% for SFI, 40.9% for FURI). Prescription antibiotics and over-the-counter medications were also reduced. The vaccine was generally safe and well tolerated with no vaccine related serious adverse events. LAIV represents an additional important option for the control of influenza.

Influenza vaccines: present and future

Immunization is the most feasible method for preventing influenza. Vaccination against influenza is recommended for everyone 65 years of age and older and for persons less than 65 years of age who are at risk for developing complications of influenza. Immune correlates of protection have been established, and a global network is in place to monitor the appearance and circulation of antigenic variants of influenza viruses, as well as the appearance of novel subtypes of influenza A. Antigenic and genetic analyses of circulating viruses and testing of serum from vaccine recipients guide vaccine composition updates. The efficacy of influenza vaccines depends in part on the closeness of the antigenic match between the vaccine strain and the epidemic strain. Currently licensed influenza vaccines are trivalent, formalin-inactivated, egg-derived vaccines; their efficacy ranges from 70 to 90% in young, healthy populations when there is a close antigenic match between vaccine strains and epidemic strains. Development of intranasally administered alternative vaccines and improvement of the existing vaccine are areas of active research. A trivalent, ca live vaccine is the most promising LAIV candidate. In a field trial, efficacy rates of LAIV in young children were 96% against influenza A (H3N2) and 91% against influenza B. However, few data are available to compare this formulation of the trivalent ca live vaccine with the trivalent, inactivated vaccine. Influenza vaccine recommendations will most likely be revised on licensure of LAIV; each vaccine may offer distinct advantages in specific populations.

Is there a role for a mucosal influenza vaccine in the elderly?

Influenza infection is an acute respiratory disease with a high morbidity and significant mortality, particularly among the elderly and individuals with chronic diseases. The majority of countries now recommend annual influenza vaccination for all people aged 65 years or older, and for those with high risk conditions. Most commercially available influenza vaccines are administered systemically and while these are effective in children and young adults, efficacy levels in elderly individuals have been reported to be much lower. Mucosal vaccines may offer an improved vaccine strategy for protection of the elderly. As the influenza virus causes a respiratory infection, it is potentially more beneficial to administer a vaccine that will boost protection in the mucosal surfaces of the upper and lower respiratory tract. Mucosal influenza vaccines are aimed at stimulating protective immunity in the respiratory tract via oral or intranasal immunisation. This review examines our present knowledge of mucosal immunity and current strategies for mucosal vaccination. It also stresses that the use of serum antibody levels as a 'surrogate marker' for protection against influenza is potentially misleading; serum antibody, for example, may be a quite inappropriate marker to assess a mucosal vaccine. This marker does not reflect other immune responses to vaccination that are crucial for protection.

Immune responses of infants to infection with respiratory viruses and live attenuated respiratory virus candidate vaccines

Respiratory viruses such as respiratory syncytial virus (RSV), the parainfluenza viruses (PIV), and the influenza viruses cause severe lower respiratory tract diseases in infants and children throughout the world. Experimental live attenuated vaccines for each of these viruses are being developed for intranasal administration in the first weeks or months of life. A variety of promising RSV, PIV-3, and influenza virus vaccine strains have been developed by classical biological methods, evaluated extensively in preclinical and clinical studies, and shown to be attenuated and genetically stable. The ongoing clinical evaluation of these vaccine candidates, coupled with recent major advances in the ability to develop genetically engineered viruses with specified mutations, may allow the rapid development of respiratory virus strains that possess ideal levels of replicative capacity and genetic stability in vivo. A major remaining obstacle to successful immunization of infants against respiratory virus associated disease may be the relatively poor immune response of very young infants to primary virus infection. This paper reviews the immune correlates of protection against disease caused by these viruses, immune responses of infants to naturally-acquired infection, and immune responses of infants to experimental infection with candidate vaccine viruses.

Influenza virus vaccination of patients with chronic lung disease

STUDY OBJECTIVES

To evaluate the safety of, and mucosal and systemic immune responses induced by two influenza virus vaccine regimens in subjects with COPD.

DESIGN

Single-center, blinded, randomized, prospective clinical trial evaluating two vaccine regimens.

SETTING

Outpatient clinics of St. Louis Department of Veterans Affairs Medical Center.

PARTICIPANTS

Volunteers (age range, 42 to 88 years) had preexisting COPD with severe obstruction to airflow on average, were male, and were not receiving immunosuppressive medication.

INTERVENTIONS

Twenty-nine volunteers were randomly assigned to receive either bivalent live attenuated influenza A virus vaccine (CAV) or saline solution placebo intranasally. All subjects also received an i.m. injection of trivalent inactivated influenza virus vaccine (TVV) simultaneously.

MEASUREMENTS AND RESULTS

Clinical status and pulmonary function measured by spirometry did not change significantly after vaccination. Using hemagglutinins (H1 and H3 HA) which more closely resembled those in CAV, mean levels of anti-HA immunoglobulin A (IgA) antibodies in nasal washings increased significantly after vaccination with CAV and TVV compared to prevaccination, but they did not increase significantly after TVV and intranasal placebo. Mean levels of influenza A virus-stimulated interleukin-2 and -4 produced by peripheral blood mononuclear cells in vitro increased significantly after administration of the combination vaccine regimen and to a lesser extent after TVV and intranasal placebo compared to respective prevaccination levels. The timing of the cytokine response appeared different following CAV and TVV compared to TVV and intranasal placebo.

CONCLUSIONS

Intranasally administered CAV was safe when given with i.m. administered TVV and there may be an immunologic advantage to administration of the combination vaccine regimen compared to TVV with intranasal placebo.

Evaluation of bivalent live attenuated influenza A vaccines in children 2 months to 3 years of age: safety, immunogenicity and dose-response

1126 children, 2 months to 3 years old, received a single intranasal dose of 10(4), 10(6), or 10(7) TCID50 of cold adapted (ca) A/Kawasaki/9/86 (H1N1) and A/Beijing/352/89 (H3N2) or placebo, in a double blind, placebo-controlled, safety and immunogenicity trial. No reactogenicity attributable to vaccine was demonstrated. A single bivalent 10(6) or 10(7) dose produced high rates of seroconversion to H1N1 (77%) and H3N2 (92%) in seronegative children > 6 months old; serologic responses were lower to H1N1 (P < 0.001) and H3N2 (P = 0.01) in younger infants. A single 10(6) dose of bivalent ca influenza A vaccine can be immunogenic in children, but response is age dependent.

Antibody efficacy as a keen index to evaluate influenza vaccine effectiveness

The efficacy of the influenza vaccine is often understimated, due to the dilution of the outcome by noninfluenzal illnesses. We thus explored the methodology to evaluate the effect of the inactivated influenza vaccine under the following strict conditions: an assessment of the effectiveness on clinical illness among healthy adults in a small-scale mixed epidemic during the 1991-1992 season. The vaccine antigens included were A/Yamagata/32/89 (H1N1), A/Beijing/352/89 (H3N2), and B/Bangkok/163/90. Two indices were analyzed: "vaccine efficacy", a comparison between the vaccinees and the nonvaccinees; and "antibody efficacy", a comparison between those with and those without a protective level of pre-epidemic hemagglutination-inhibition (HAI) antibody. The odds ratio (OR) and its 95% confidence interval (95% CI) was calculated by the logistic regression model. A decrease in the age-adjusted OR of vaccination was not statistically significant: 0.54 (95% CI: 0.19-1.53) corresponding to vaccine efficacy (1-OR) of 46% (-53% to 81%). Among the vaccinees, a significantly decreased OR in those with a higher titer to A/Beijing was observed: 0.14 (0.02-0.92) adjusted for the mutual effects of pre-epidemic antibodies to different vaccine antigens. The adjusted ORs thus calculated for A/Yamagata and B/Bangkok were not found to be statistically significant. The antibody efficacy (1-OR) was estimated to be 86% (8% to 98%) against illnesses related to A/Beijing-like viruses. The product of antibody efficacy (86%) and the proportion of those who achieved a protective level of antibody after vaccination (73% for A/Beijing strain) was 63%, which is theoretically equivalent to the vaccine efficacy. Thus, the antibody efficacy is considered to be an important index, while the vaccine efficacy against clinical illnesses is easily disturbed by extraneous factors in the field trials.

Studies on reactogenicity and immunogenicity of attenuated bivalent cold recombinant influenza type A (CRA) and inactivated trivalent influenza virus (TI) vaccines in infants and young children

Fifty-two infants seronegative to or without prior infection with influenza type A viruses were enrolled in a study to evaluate reactogenicity and immunogenicity of three bivalent cold recombinant type A (CRA) and two trivalent inactivated influenza (TI) vaccines. Controls consisted of infants receiving normal saline by nose drops (Pli.n.) or intramuscularly (Pli.m.). CRA and TI vaccines were monitored for local and systemic reactions after vaccination. Serum specimens obtained prior to and 6 weeks postvaccination were analysed for neutralizing antibody to influenza H1N1 and H3N2 viruses. CRA vaccines and Pli.n. recipients had similar numbers of acute respiratory infections and comparable rates of illnesses during the trial. Significantly fewer CRA vaccinees without an intercurrent viral infection had fever (0/16 versus 4/10, p = 0.04) and cough (4/16 versus 9/10, p = 0.002) than CRA vaccinees with a confirmed intercurrent viral infection. Recipients of TI vaccine and Pli.m. did not develop reactions at the injection site. For each of the CRA vaccines tested, a dominant CRA virus was identified. The dominant CRA viruses were isolated from a greater number of infants or for a longer duration than the non-dominant CRA viruses. All 14 non-dominant CRA viruses were recovered from infants within the first week after vaccination; 24 of 77 dominant CRA viruses were recovered more than 7 days after vaccination. The immunogenicity of CRA vaccines was not affected by a confirmed intercurrent viral infection or low titres of influenza-specific antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunization of institutionalized asthmatic children and patients with psychomotor retardation using live attenuated cold-adapted reassortment influenza A H1N1, H3N2 and B vaccines

Live attenuated cold-adapted reassortant (CR) influenza virus vaccines were evaluated in institutionalized asthmatic children and severe psychomotor-retarded (SPR) patients. Almost all the vaccinees were seropositive to the vaccine strains before immunization. Trivalent CR vaccine (containing A H1N1 (CR-125), A H3N2 (CR-149) and B (CRB-117)), bivalent CR vaccine (CR-125 and CR-149) and monovalent CRB-117 were inoculated to 19 asthmatic children and 36 and 16 SPR patients, respectively. Overall 49, 22, and 11% of vaccinees were infected by A H1N1, A H3N2 or B vaccine viruses, respectively, as indicated by significant haemagglutination-inhibition (HI) antibody titre rises 4 weeks after inoculation. No severe adverse reactions associated with CR vaccination were observed in the handicapped patients. A nosocomial outbreak of influenza A H1N1 occurred in the ward with asthmatic children, but none of the 19 CR-trivalent vaccinees became infected. However, five of 20 non-vaccinees in the same ward, and ten of 30 vaccinees in another ward that received inactivated split vaccine became infected. The CR vaccines demonstrated significant protective effects against natural exposure to the A H1N1 virus, and were well tolerated and safe when given to patients with bronchial asthma and severe psychomotor retardation.

Evaluation of a live attenuated, cold-adapted parainfluenza virus type 3 vaccine in children

Cold passage 18 (CP18) parainfluenza virus type 3 (PIV-3) vaccine was evaluated in a double-blind, randomized, placebo-controlled study of 95 infants and young children. None of 19 seropositive older children 41 to 124 months old became infected when 10(6) 50% tissue culture infective doses (TCID50) of vaccine virus was administered intranasally. Two of nine and seven of twenty-four young seropositive children given 10(5) or 10(6) TCID50 of CP18 PIV-3, respectively, became infected. Each of four seronegative young children became infected, as indicated by virus shedding and antibody response, when given 10(6) TCID50 of CP18 PIV-3 intranasally. Illness was not observed in seropositive children. Two of the four seronegative children developed a mild illness characterized by rhinorrhea and wheezing on auscultation; none had fever. In one case, vaccine virus spread from a vaccine to a sibling control but did not cause illness. The vaccine is attenuated relative to wild-type PIV-3, but additional attenuation will be required to achieve a satisfactory PIV-3 vaccine.

Reduced infectivity of cold-adapted influenza A H1N1 viruses in the elderly: correlation with serum and local antibodies

OBJECTIVE

To compare young and elderly adults in terms of their immune responses and rates of infection following intranasal vaccination with a live attenuated influenza virus.

DESIGN

Time series, comparing outcomes in young and elderly convenience sample.

METHOD

Retrospective laboratory analysis of serum and nasal wash specimens collected during prior studies in which young or elderly volunteers had been inoculated with cold-adapted influenza A/Kawasaki/86 (H1N1) reassortant virus.

SETTING

Johns Hopkins Center for Immunization Research.

PARTICIPANTS

Healthy young and elderly adults with pre-vaccination serum hemagglutination inhibition (HAI) antibody titers less than or equal to 1:8.

OUTCOME MEASUREMENTS

Antibody responses in serum and nasal washes.

MAIN RESULTS

The proportion of vaccinees who developed any serum or local antibody response was higher in young compared with elderly subjects (20/20 vs 5/14, P less than 0.0005). Resistance to infection with cold-adapted virus correlated with pre-vaccination levels of serum immunoglobulin G (IgG), serum IgA, and nasal wash IgA antibody to whole virus antigen. Age was highly correlated with a lack of response to vaccine by simple regression, but not when data were adjusted for pre-existing antibody levels.

CONCLUSIONS

Cold-adapted reassortant influenza A H1N1 viruses achieve lower rates of infection in elderly than young adults, primarily due to age-related differences in preexisting levels of immunity which may not be reflected by HAI titer.

In elderly persons live attenuated influenza A virus vaccines do not offer an advantage over inactivated virus vaccine in inducing serum or secretory antibodies or local immunologic memory

In a double-blind, randomized trial, 102 healthy elderly subjects were inoculated with one of four preparations: (i) intranasal bivalent live attenuated influenza vaccine containing cold-adapted A/Kawasaki/86 (H1N1) and cold-adapted A/Bethesda/85 (H3N2) viruses; (ii) parenteral trivalent inactivated subvirion vaccine containing A/Taiwan/86 (H1N1), A/Leningrad/86 (H3N2), and B/Ann Arbor/86 antigens; (iii) both vaccines; or (iv) placebo. To determine whether local or systemic immunization augmented mucosal immunologic memory, all volunteers were challenged intranasally 12 weeks later with the inactivated virus vaccine. We used a hemagglutination inhibition assay to measure antibodies in sera and a kinetic enzyme-linked immunosorbent assay to measure immunoglobulin G (IgG) and IgA antibodies in sera and nasal washes, respectively. In comparison with the live virus vaccine, the inactivated virus vaccine elicited higher and more frequent rises of serum antibodies, while nasal wash antibody responses were similar. The vaccine combination induced serum and local antibodies slightly more often than the inactivated vaccine alone did. Coadministration of live influenza A virus vaccine did not alter the serum antibody response to the influenza B virus component of the inactivated vaccine. The anamnestic nasal antibody response elicited by intranasal inactivated virus challenge did not differ in the live, inactivated, or combined vaccine groups from that observed in the placebo group not previously immunized. These results suggest that in elderly persons cold-adapted influenza A virus vaccines offer little advantage over inactivated virus vaccines in terms of inducing serum or secretory antibody or local immunological memory. Studies are needed to determine whether both vaccines in combination are more efficacious than inactivated vaccine alone in people in this age group.

Systemic and local antibody responses in elderly subjects given live or inactivated influenza A virus vaccines

Intranasal live attenuated cold-adapted (ca) influenza A/Kawasaki/9/86 (H1N1) reassortant virus and parenteral inactivated influenza A/Taiwan/1/86 (H1N1) virus were given alone or in combination to 80 ambulatory elderly subjects. An enzyme-linked immunosorbent assay was used to measure hemagglutinin-specific (HA) antibodies in serum and nasal wash specimens collected before vaccination and 1 and 3 months later. Serum immunoglobulin G (IgG) and nasal wash IgA HA responses were elicited in 56 and 20%, respectively, of 25 inactivated-virus vaccinees and in 67 and 48%, respectively, of 27 recipients of both vaccines but in only 36 and 25%, respectively, of 28 vaccinees given live virus alone. Inactivated virus, administered alone or with live virus vaccine, induced higher titers of serum antibody than did the live virus alone. In contrast, nasal IgA HA antibody was elicited more often and in greater quantity by the vaccine combination than by either vaccine alone. Despite these differences, the peak titers of local antibody mounted by each group of vaccinees were similar. By 3 months postvaccination, serum IgG and nasal IgA HA antibody titers remained elevated above prevaccination levels in 50 and 17%, respectively, of the inactivated-virus vaccinees and in 46 and 23%, respectively, of recipients of both vaccines but in only 19 and 7%, respectively, of the live-virus and systemic antibodies, if vaccinees. The finding that live ca influenza A virus induced short-lived local and systemic antibodies, if confirmed, suggests that live virus vaccination may not be a suitable alternative or adjunct to inactivated virus vaccination for the elderly.

Evaluation of cold-recombinant influenza A/Korea (CR-59) virus vaccine in infants

Twenty-four infants 5 to 13 months of age were intranasally vaccinated with a live cold-recombinant influenza A/Korea (CR-59, H3N2) virus vaccine. Nineteen infants served as controls. The inocula ranged from 10(3.2) to 10(6.2) 50% tissue culture infective doses (TCID50) per infant. Zero of six, one of four, seven of ten, and four of four infants receiving 10(3.2), 10(4.2), 10(5.2), and 10(6.2) TCID50, respectively, were infected by the intranasal vaccine. The amount of virus required to infect 50% of infants was calculated to be 10(4.6) TCID50. The occurrence of fever, respiratory illness, and otitis media was common among both controls and vaccinees in the postinoculation period. Maternal antibody was present in low titers in some infants and did not inhibit replication of the vaccine virus.

Local and systemic antibody responses in high-risk adults given live-attenuated and inactivated influenza A virus vaccines

Forty seropositive older adults with chronic diseases were vaccinated intranasally with either influenza A/California/10/78 (H1N1) (CR37) or influenza A/Washington/897/80 (H3N2) (CR48) virus. No clinically significant decrements in pulmonary function occurred postvaccination. Eight (62%) recipients of CR37 virus and 16 (59%) recipients of CR48 virus became infected with vaccine virus, as indicated by a fourfold rise in nasal wash immunoglobulin G (IgG) or IgA antibody titer, a fourfold rise in serum antibody titer, isolation of vaccine virus from nasal washings, or all of these. Within 2 years after cold-recombinant virus vaccination, 29 vaccinees received trivalent inactivated influenza virus vaccine parenterally. After inactivated virus vaccination, 23 (79%) vaccinees developed a fourfold rise in nasal wash or serum antibody titer to H1 antigen and 24 (83%) developed a fourfold rise in nasal wash or serum antibody titer to H3 antigen. Significantly more cold-recombinant virus vaccinees developed a fourfold rise in nasal wash IgA antibody to H1 or H3 hemagglutinin compared with inactivated virus vaccinees (17 [43%] versus 9 [17%], P = 0.01). We conclude that these cold-recombinant virus vaccines are safe and immunogenic in seropositive older high-risk adults and more often induced a nasal wash IgA antibody response than the inactivated virus vaccine.

Safety of and serum antibody response to cold-recombinant influenza A and inactivated trivalent influenza virus vaccines in older adults with chronic diseases

Forty older adults with chronic diseases were vaccinated intranasally with either influenza A/California/10/78 (H1N1) (CR37) or influenza A/Washington/897/80 (H3N2) (CR48) virus. No clinically significant morbidity or decrement in pulmonary function occurred postvaccination. Two (15%) recipients of CR37 virus and twelve (44%) recipients of CR48 virus became infected with vaccine virus, as indicated by a fourfold rise in serum hemagglutination inhibition antibody titer; a fourfold rise in serum immunoglobulin G (IgG) or IgA antibody titer, indicated by enzyme-linked immunosorbent assay; isolation of vaccine virus from nasal washings; or all of these. Within 1 year after cold-recombinant vaccine virus vaccination, 18 vaccines received inactivated trivalent influenza virus vaccine parenterally. Of the vaccinees, 13 (72%) developed a fourfold rise in serum antibody titer to H1N1 antigen and 16 (89%) developed a fourfold rise in serum antibody titer to H3N2 antigen. We conclude that administration of these cold-recombinant vaccine viruses to older adults with chronic diseases was safe, but that serum antibody response rates were lower than those achieved with subsequently administered inactivated influenza virus vaccine given parenterally. However, the higher seroconversion rates attained by using the inactivated trivalent influenza virus vaccine do not necessarily mean that it is more efficacious in preventing infection or severe illness or both due to natural wild-type influenza A virus.

Comparative studies of wild-type and cold-mutant (temperature-sensitive) influenza virus: detection of mutations in all genes of the A/Ann Arbor/6/60 (H2N2) mutant vaccine donor strain

Direct biochemical evidence has been obtained for the existence of mutations in all eight RNA segments of the A/Ann Arbor/6/60 cold-adapted (ca) mutant influenza virus strain as compared with its wild-type (wt) progenitor. Polyacrylamide gel electrophoresis (PAGE) of viral RNA revealed a change in the electrophoretic migration of RNA 2 (PB1). T1 oligonucleotide mapping revealed changes in two polymerase genes (the PB2 and PA genes), the hemagglutinin (HA) gene and the nucleoprotein (NP) gene. Analysis of S1 nuclease-treated RNA hybrids on polyacrylamide gels detected changes in the HA and neuraminidase (NA) genes. Partial DNA sequence analysis demonstrated a base sequence change in the matrix (M) protein gene that predicts an amino acid change in the M2 protein and a silent mutation in the non-structural (NS) protein gene. In addition, analysis of viral polypeptides by PAGE has so far revealed changes in the viral protein, PA. These findings directly demonstrate the existence of multiple mutations in the ca vaccine strain, a property that may provide reliably and stably attenuated vaccines that derive their six internal genes from the ca A/Ann Arbor/6/60 donor strain.

Protection of weanling hamsters from experimental infection with wild-type parainfluenza virus type 3 (para 3) by cold-adapted mutants of para 3

Parainfluenza virus type 3 (para 3) was adapted to replicate at 20 degrees C, a nonpermissive temperature for wild-type (wt) para 3. Serial passage at 20 degrees C resulted in the generation of cold-adapted (ca) and temperature-sensitive (ts) mutants. These mutant viruses have been characterized both in vitro and in vivo [Belshe and Hissom (1982): Journal of Medical Virology 10:235-242; Crookshanks and Belshe (1984): Journal of Medical Virology 13:243-249]. We now report the evaluation of three mutants (clone 1150, passaged 12 times in the cold [cp12], clone 1146, passaged 18 times in the cold [cp18], and clone 1328, passaged 45 times in the cold [cp45]) for their ability to protect hamsters from infection by wild-type para 3. Ether-anesthetized male syrian hamsters were intranasally vaccinated with either wt para 3 (clone 127) or one of the ca para 3 mutants and on day 28 post-vaccination; each animal was intranasally challenged with 10(5.0) pfu of wt para 3. On days 1, 2, 3, and 4 post-challenge, 4 to 13 hamsters from each group were sacrificed, and the quantity of para 3 in the nasal turbinates and lungs was determined. Wt virus induced protection from challenge. cp12, cp18, and cp45 reduced the peak titer of wt replication in the lungs by greater than 100-fold, tenfold, and tenfold, respectively. The duration of virus replication was shortened also by intranasal vaccination with the mutants. These data give evidence of an inverse relationship between the degree of protection induced by vaccination with cold-adapted mutants and the number of passages of the virus in the cold.