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Vaccines for preventing influenza in healthy adults.

Abstract

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.

Authors+Show Affiliations

Vaccines Field, The Cochrane Collaboration, Via Adige 28a, Anguillara Sabazia, Roma, Italy, 00061.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Meta-Analysis
Review
Systematic Review

Language

eng

PubMed ID

20614424

Citation

Jefferson, Tom, et al. "Vaccines for Preventing Influenza in Healthy Adults." The Cochrane Database of Systematic Reviews, 2010, p. CD001269.
Jefferson T, Di Pietrantonj C, Rivetti A, et al. Vaccines for preventing influenza in healthy adults. Cochrane Database Syst Rev. 2010.
Jefferson, T., Di Pietrantonj, C., Rivetti, A., Bawazeer, G. A., Al-Ansary, L. A., & Ferroni, E. (2010). Vaccines for preventing influenza in healthy adults. The Cochrane Database of Systematic Reviews, (7), CD001269. https://doi.org/10.1002/14651858.CD001269.pub4
Jefferson T, et al. Vaccines for Preventing Influenza in Healthy Adults. Cochrane Database Syst Rev. 2010 Jul 7;(7)CD001269. PubMed PMID: 20614424.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Vaccines for preventing influenza in healthy adults. AU - Jefferson,Tom, AU - Di Pietrantonj,Carlo, AU - Rivetti,Alessandro, AU - Bawazeer,Ghada A, AU - Al-Ansary,Lubna A, AU - Ferroni,Eliana, Y1 - 2010/07/07/ PY - 2010/7/9/entrez PY - 2010/7/9/pubmed PY - 2010/8/12/medline SP - CD001269 EP - CD001269 JF - The Cochrane database of systematic reviews JO - Cochrane Database Syst Rev IS - 7 N2 - 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. SN - 1469-493X UR - https://www.unboundmedicine.com/medline/citation/20614424/Vaccines_for_preventing_influenza_in_healthy_adults_ L2 - https://doi.org/10.1002/14651858.CD001269.pub4 DB - PRIME DP - Unbound Medicine ER -