Studies in man with a cold-recombinant live influenza B virus vaccine

Vaccines for preventing influenza in healthy adults

BACKGROUND

The consequences of influenza in adults are mainly time off work. Vaccination of pregnant women is recommended internationally. This is an update of a review published in 2014. Future updates of this review will be made only when new trials or vaccines become available. Observational data included in previous versions of the review have been retained for historical reasons but have not been updated due to their lack of influence on the review conclusions.

OBJECTIVES

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in healthy adults, including pregnant women.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 12), MEDLINE (January 1966 to 31 December 2016), Embase (1990 to 31 December 2016), the WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017), and ClinicalTrials.gov (1 July 2017), as well as checking the bibliographies of retrieved articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy individuals aged 16 to 65 years. Previous versions of this review included observational comparative studies assessing serious and rare harms cohort and case-control studies. Due to the uncertain quality of observational (i.e. non-randomised) studies and their lack of influence on the review conclusions, we decided to update only randomised evidence. The searches for observational comparative studies are no longer updated.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We rated certainty of evidence for key outcomes (influenza, influenza-like illness (ILI), hospitalisation, and adverse effects) using GRADE.

MAIN RESULTS

We included 52 clinical trials of over 80,000 people assessing the safety and effectiveness of influenza vaccines. We have presented findings from 25 studies comparing inactivated parenteral influenza vaccine against placebo or do-nothing control groups as the most relevant to decision-making. The studies were conducted over single influenza seasons in North America, South America, and Europe between 1969 and 2009. We did not consider studies at high risk of bias to influence the results of our outcomes except for hospitalisation.Inactivated influenza vaccines probably reduce influenza in healthy adults from 2.3% without vaccination to 0.9% (risk ratio (RR) 0.41, 95% confidence interval (CI) 0.36 to 0.47; 71,221 participants; moderate-certainty evidence), and they probably reduce ILI from 21.5% to 18.1% (RR 0.84, 95% CI 0.75 to 0.95; 25,795 participants; moderate-certainty evidence; 71 healthy adults need to be vaccinated to prevent one of them experiencing influenza, and 29 healthy adults need to be vaccinated to prevent one of them experiencing an ILI). The difference between the two number needed to vaccinate (NNV) values depends on the different incidence of ILI and confirmed influenza among the study populations. Vaccination may lead to a small reduction in the risk of hospitalisation in healthy adults, from 14.7% to 14.1%, but the CI is wide and does not rule out a large benefit (RR 0.96, 95% CI 0.85 to 1.08; 11,924 participants; low-certainty evidence). Vaccines may lead to little or no small reduction in days off work (-0.04 days, 95% CI -0.14 days to 0.06; low-certainty evidence). Inactivated vaccines cause an increase in fever from 1.5% to 2.3%.We identified one RCT and one controlled clinical trial assessing the effects of vaccination in pregnant women. The efficacy of inactivated vaccine containing pH1N1 against influenza was 50% (95% CI 14% to 71%) in mothers (NNV 55), and 49% (95% CI 12% to 70%) in infants up to 24 weeks (NNV 56). No data were available on efficacy against seasonal influenza during pregnancy. Evidence from observational studies showed effectiveness of influenza vaccines against ILI in pregnant women to be 24% (95% CI 11% to 36%, NNV 94), and against influenza in newborns from vaccinated women to be 41% (95% CI 6% to 63%, NNV 27).Live aerosol vaccines have an overall effectiveness corresponding to an NNV of 46. The performance of one- or two-dose whole-virion 1968 to 1969 pandemic vaccines was higher (NNV 16) against ILI and (NNV 35) against influenza. There was limited impact on hospitalisations in the 1968 to 1969 pandemic (NNV 94). The administration of both seasonal and 2009 pandemic vaccines during pregnancy had no significant effect on abortion or neonatal death, but this was based on observational data sets.

AUTHORS' CONCLUSIONS

Healthy adults who receive inactivated parenteral influenza vaccine rather than no vaccine probably experience less influenza, from just over 2% to just under 1% (moderate-certainty evidence). They also probably experience less ILI following vaccination, but the degree of benefit when expressed in absolute terms varied across different settings. Variation in protection against ILI may be due in part to inconsistent symptom classification. Certainty of evidence for the small reductions in hospitalisations and time off work is low. Protection against influenza and ILI in mothers and newborns was smaller than the effects seen in other populations considered in this review.Vaccines increase the risk of a number of adverse events, including a small increase in fever, but rates of nausea and vomiting are uncertain. The protective effect of vaccination in pregnant women and newborns is also very modest. We did not find any evidence of an association between influenza vaccination and serious adverse events in the comparative studies considered in this review. Fifteen included RCTs were industry funded (29%).

Duration of Virus Shedding After Trivalent Intranasal Live Attenuated Influenza Vaccination in Adults

Objective:

To characterize the probability and duration of viral shedding among adults given trivalent live attenuated influenza vaccine (LATV).

Design:

Prospective surveillance study.

Methods:

Nasal wash samples were collected from adult volunteers at baseline and on days 3, 7, and 10 and between days 17 and 21 following intranasal LAIV vaccination. The presence, titer, and identification of each specific strain of influenza virus shed were determined by standard methodology.

Results:

Twenty subjects received LATV. No samples were positive for influenza virus at baseline. After LAIV vaccination, influenza virus was recovered from 10 of 20 vaccinees on day 3, from 1 of 18 vaccinees on day 7, and from none of the samples on days 10 or 17 through 21. Vaccinees who shed vaccine virus were significantly younger than those who did not (mean age, 26.4 vs 38.6 years;P< .01). Although the presence of specific mucosal immunoglobulin A to influenza B was associated with significantly less shedding of influenza B after vaccination (P= .02), associations of shedding with other measures of immunity were not detected.

Conclusion:

The duration of shedding of vaccine virus after LAIV in adults is limited and may be associated with an individual's prior influenza vaccination history.

Vaccines for preventing influenza in healthy adults

BACKGROUND

Different types of influenza vaccines are currently produced worldwide. Vaccination of pregnant women is recommended internationally, while healthy adults are targeted in North America.

OBJECTIVES

To identify, retrieve and assess all studies evaluating the effects (efficacy, effectiveness and harm) of vaccines against influenza in healthy adults, including pregnant women.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 2), MEDLINE (January 1966 to May 2013) and EMBASE (1990 to May 2013).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy individuals aged 16 to 65 years. We also included comparative studies assessing serious and rare harms.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included 90 reports containing 116 data sets; among these 69 were clinical trials of over 70,000 people, 27 were comparative cohort studies (about eight million people) and 20 were case-control studies (nearly 25,000 people). We retrieved 23 reports of the effectiveness and safety of vaccine administration in pregnant women (about 1.6 million mother-child couples).The overall effectiveness of parenteral inactivated vaccine against influenza-like illness (ILI) is limited, corresponding to a number needed to vaccinate (NNV) of 40 (95% confidence interval (CI) 26 to 128). The overall efficacy of inactivated vaccines in preventing confirmed influenza has a NNV of 71 (95% CI 64 to 80). The difference between these two values depends on the different incidence of ILI and confirmed influenza among the study populations: 15.6% of unvaccinated participants versus 9.9% of vaccinated participants developed ILI symptoms, whilst only 2.4% and 1.1%, respectively, developed laboratory-confirmed influenza.No RCTs assessing vaccination in pregnant women were found. The only evidence available comes from observational studies with modest methodological quality. On this basis, vaccination shows very limited effects: NNV 92 (95% CI 63 to 201) against ILI in pregnant women and NNV 27 (95% CI 18 to 185) against laboratory-confirmed influenza in newborns from vaccinated women.Live aerosol vaccines have an overall effectiveness corresponding to a NNV 46 (95% CI 29 to 115).The performance of one-dose or two-dose whole virion pandemic vaccines was higher, showing a NNV of 16 (95% CI 14 to 20) against ILI and a NNV of 35 (95% CI 33 to 47) against influenza, while a limited impact on hospitalisation was found (NNV 94, 95% CI 70 to 1022).Vaccination had a modest effect on time off work and had no effect on hospital admissions or complication rates. Inactivated vaccines caused local harms. No evidence of association with serious adverse events was found, but the harms evidence base was limited.The overall risk of bias in the included trials is unclear because it was not possible to assess the real impact of bias.

AUTHORS' CONCLUSIONS

Influenza vaccines have a very modest effect in reducing influenza symptoms and working days lost in the general population, including pregnant women. No evidence of association between influenza vaccination and serious adverse events was found in the comparative studies considered in the review. This review includes 90 studies, 24 of which (26.7%) were funded totally or partially by industry. Out of the 48 RCTs, 17 were industry-funded (35.4%).

Vaccines for preventing influenza in healthy adults

BACKGROUND

Different types of influenza vaccines are currently produced worldwide. Healthy adults are presently targeted mainly in North America.

OBJECTIVES

Identify, retrieve and assess all studies evaluating the effects of vaccines against influenza in healthy adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2010, issue 2), MEDLINE (January 1966 to June 2010) and EMBASE (1990 to June 2010).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally-occurring influenza in healthy individuals aged 16 to 65 years. We also included comparative studies assessing serious and rare harms.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included 50 reports. Forty (59 sub-studies) were clinical trials of over 70,000 people. Eight were comparative non-RCTs and assessed serious harms. Two were reports of harms which could not be introduced in the data analysis. In the relatively uncommon circumstance of vaccine matching the viral circulating strain and high circulation, 4% of unvaccinated people versus 1% of vaccinated people developed influenza symptoms (risk difference (RD) 3%, 95% confidence interval (CI) 2% to 5%). The corresponding figures for poor vaccine matching were 2% and 1% (RD 1, 95% CI 0% to 3%). These differences were not likely to be due to chance. Vaccination had a modest effect on time off work and had no effect on hospital admissions or complication rates. Inactivated vaccines caused local harms and an estimated 1.6 additional cases of Guillain-Barré Syndrome per million vaccinations. The harms evidence base is limited.

AUTHORS' CONCLUSIONS

Influenza vaccines have a modest effect in reducing influenza symptoms and working days lost. There is no evidence that they affect complications, such as pneumonia, or transmission.WARNING: This review includes 15 out of 36 trials funded by industry (four had no funding declaration). An earlier systematic review of 274 influenza vaccine studies published up to 2007 found industry funded studies were published in more prestigious journals and cited more than other studies independently from methodological quality and size. Studies funded from public sources were significantly less likely to report conclusions favorable to the vaccines. The review showed that reliable evidence on influenza vaccines is thin but there is evidence of widespread manipulation of conclusions and spurious notoriety of the studies. The content and conclusions of this review should be interpreted in light of this finding.

Viral infections of the respiratory tract: prevention and treatment

The rapid discovery of specific viral agents as the cause of many acute respiratory diseases was accompanied by considerable optimism that vaccines or other control measures could be developed quickly. Subsequent experience has demonstrated that effective control of these important public health problems has been an elusive goal. However, recent exciting developments in our understanding of the molecular biology and immunology of these viruses may provide the basis for more effective strategies in the future.

Vaccines for preventing influenza in healthy adults

BACKGROUND

Different types of influenza vaccines are currently produced world-wide. Healthy adults are at present targeted only in North America. Despite the publication of a large number of clinical trials, there is still substantial uncertainty about the clinical effectiveness of influenza vaccines and this has a negative impact on their acceptance and uptake.

OBJECTIVES

To identify, retrieve and assess all studies evaluating the effects (efficacy, effectiveness and harms) of vaccines against influenza in healthy adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2005) which contains the Cochrane Acute Respiratory Infections Group trials register; MEDLINE (January 1966 to January 2006); and EMBASE (1990 to January 2006). We wrote to vaccine manufacturers and first or corresponding authors of studies in the review.

SELECTION CRITERIA

Any randomised or quasi-randomised studies comparing influenza vaccines in humans with placebo, no intervention. Live, attenuated, or killed vaccines or fractions of them administered by any route, irrespective of antigenic configuration were assessed. Only studies assessing protection from exposure to naturally occurring influenza in healthy individuals aged 16 to 65 years were considered. Comparative non-randomised studies were included if they assessed evidence of the possible association between influenza vaccines and serious harms.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

Forty-eight reports were included: 38 (57 sub-studies) were clinical trials providing data about effectiveness, efficacy and harms of influenza vaccines and involved 66,248 people; 8 were comparative non-randomised studies and tested the association of the vaccines with serious harms; 2 were reports of harms which could not be introduced in the data analysis. Inactivated parenteral vaccines were 30% effective (95% CI 17% to 41%) against influenza-like illness, and 80% (95% CI 56% to 91%) efficacious against influenza when the vaccine matched the circulating strain and circulation was high, but decreased to 50% (95% CI 27% to 65%) when it did not. Excluding the studies of the 1968 to 1969 pandemic, effectiveness was 15% (95% CI 9% to 22%) and efficacy was 73% (95% CI 53% to 84%). Vaccination had a modest effect on time off work, but there was insufficient evidence to draw conclusions on hospital admissions or complication rates. Inactivated vaccines caused local tenderness and soreness and erythema. Spray vaccines had more modest performance. Monovalent whole-virion vaccines matching circulating viruses had high efficacy (VE 93%, 95% CI 69% to 98%) and effectiveness (VE 66%, 95% CI 51% to 77%) against the 1968 to 1969 pandemic.

AUTHORS' CONCLUSIONS

Influenza vaccines are effective in reducing cases of influenza, especially when the content predicts accurately circulating types and circulation is high. However, they are less effective in reducing cases of influenza-like illness and have a modest impact on working days lost. There is insufficient evidence to assess their impact on complications. Whole-virion monovalent vaccines may perform best in a pandemic.

A placebo-controlled dose response study of the reactogenicity and immunogenicity of a live cold-recombinant influenza B virus vaccine in healthy volunteers

A live cold-recombinant influenza B virus vaccine (RB77) was given intranasally in a placebo-controlled, double blind study to volunteers in dosages of 10(7.9) EID50/ml, 10(7.25) EID50/ml, 10(5.7) EID50/ml. The tolerability, safety, and immunogenicity of the vaccine were investigated. No revertant virus was found in nasal swabs taken after immunisation. Local reactions were mild and showed a significant increase over the placebo only in the highest dose group. Systemic reactions were not different from the placebo. A significant increase in haemagglutinin inhibition titre was found in the highest dose group against the immunising strain (RB77) and the two wild strains B/TEC and B/Sing.

A mutation in the PA protein gene of cold-adapted B/Ann Arbor/1/66 influenza virus associated with reversion of temperature sensitivity and attenuated virulence

Reassortant SG3 inherits only the acidic polymerase (PA) protein gene from the cold-adapted B/AA/1/66 influenza virus (ca B/AA/1/66) and all remaining genes from a virulent, wild-type virus. This reassortant demonstrates attenuated virulence in ferrets and expresses a ts phenotype characteristic of the ca parent. During virulence evaluation of SG3, a virulent, non-ts revertant virus (designated SG3rFL) was isolated from the lungs of one ferret. In order to determine whether the reversion of SG3 resulted from mutation of the PA gene and/or as the result of extragenic supressor mutations, the revertant PA gene of SG3rFL was transferred to a reassortant (SG3r) inheriting only the revertant PA gene from SG3rFL and all remaining genes from SG3. Reassortant SG3r was non-ts and virulent, indicating that mutation of the PA gene was sufficient for the reversion of the ts and attenuation phenotypes expressed by SG3rFL. The nucleotide and predicted amino acid sequences of the SG3rFL PA gene were determined and compared to those of wt and ca B/AA/1/66. The predicted PA proteins of wt and ca B/AA/1/66 are known to differ by six amino acid substitutions including a valine to methionine substitution at residue 431. The PA proteins of ca B/AA/1/66 and SG3rFL were distinguished by only the single amino acid substitution of methionine to isoluecine also occurring at residue 431. Thus, the methionine residue was implicated in the attenuation of ca B/AA/1/66 and its reassortants. The hydropathic properties of valine, isoleucine, and methionine suggested that reversion involved the restoration of hydrophobic character at this site.

Sequence comparison of wild-type and cold-adapted B/Ann Arbor/1/66 influenza virus genes

Consensus sequences for both wt and ca B/Ann Arbor/1/66 viral PB2, PB1, PA, NP, M, and NS genes were directly determined from vRNA using a combination of chemical and chain-termination sequencing methods. There were 105 sites of difference between the wt and ca sets of these six RNA genes. The differences resulted in 26 amino acid substitutions distributed over the six proteins. The sequence changes were compared to the sequences of other known influenza type B wt viruses to pinpoint those changes that were unique to the ca B/ann Arbor/1/66 virus. Of the 26 amino acid differences, only 11 were unique to the cold-adapted virus. These unique sites were distributed among five of the six genes. The NS protein had no amino acid substitutions. The sequence changes are discussed in terms of their probable mode of origin and selection, and in terms of their importance to the cold-adapted, temperature-sensitive, and attenuation phenotypes of ca B/AA/1/66 virus. The sequence and organization of the PB2 gene and predicted protein are also given. The PB2 gene was 2396 nucleotides long, and it encoded a predicted protein of 770 amino acids with a molecular weight of 88,035 Da for the wt virus and 88,072 Da for the ca virus. Both proteins were predominantly hydrophilic, and each had an overall charge of +24.5 at pH 7.0.

Genetics of cold-adapted B/Ann Arbor/1/66 influenza virus reassortants: the acidic polymerase (PA) protein gene confers temperature sensitivity and attenuated virulence

The cold-adapted B/Ann Arbor/1/66 influenza virus (ca B/AA/1/66) expresses temperature-sensitive (ts), cold-adapted (ca) and attenuation phenotypes. Reassortants which inherit one or more genes from ca B/AA/1/66 and all other genes from a virulent, wild-type influenza virus, B/Houston/1732/76, were produced and evaluated in order to identify the gene(s) responsible for the ts, ca and attenuation phenotypes. Only reassortants which inherited the PA gene from ca B/AA/1/66 expressed the ts phenotype in MDCK cells at 39 degrees C. None of the reassortants tested expressed the ca phenotype in embryonated eggs at 25 degrees C. The virulence of several reassortants was evaluated in ferrets. Inheritance of the PA gene from ca B/AA/1/66 was correlated with significant febrile attenuation and the apparent restriction of viral replication in the lower respiratory tract. Isolation of a virulent, non-ts revertant virus inheriting only the PA gene from ca B/AA/1/66 established a direct relationship between expression of the ts phenotype and attenuated virulence. Evidence for the contribution of at least one other gene from ca B/AA/1/66 to attenuation was observed. Thus, based on the methods used to determine reassortant gene compositions, these results indicate that the PA gene is primarily responsible for attenuation of ca B/AA/1/66 and its reassortants.

The use of the single radial haemolysis test for assessing antibody response and protective antibody levels in an influenza B vaccine study

Single radial haemolysis (SRH) and HAI tests were used to determine the levels of antibody in sera obtained from 118 volunteers taking part in a study of influenza B/Hong Kong/73 subunit vaccine. The two tests gave similar overall results, and showed good correlation, but SRH appeared to be more sensitive for the detection of low concentrations of antibody. A greater than or equal to 45% increase in SRH zone area was found to be equivalent to a significant increase in antibody titre and on the basis of this value, the HAI and SRH tests gave similar results for responses to immunization. The concentration of antibody equivalent to a 50% protective level against a challenge virus infection was a zone area of 45 mm2 for the SRH test; this was equivalent to an HAI titre of 1:20 which has previously been established as the 50% protective level.