Posted by: Chris Maloney | January 18, 2013

Will The Flu Shot Protect Me From This Year’s Flu?

110925-N-SF704-056.jpg

110925-N-SF704-056.jpg (Photo credit: Commander, U.S. 7th Fleet)

Short answer: maybe, depending on your age.

Full answer:  Every year the CDC estimates the effectiveness of the vaccine.  This year’s estimate is 62% (Complete study abstract below).  If you look at the Lancet meta-analysis of all the studies, the average effectiveness rate is 69%.  So we’re not doing well even by the CDC’s estimates.

For the uninitiated, effectiveness is an estimate based on observation, not on a randomized, double-blind study.  For those results we have to look backward a couple of years.

Here I quote last year’s Cochrane Database meta-analysis, starting with their conclusion (complete abstract below):  “The review showed that reliable evidence on influenza vaccines is thin but there is evidence of widespread manipulation of conclusions.”  For the uninitiated, these are more than fighting words; these are the equivalent of flipping the bird to the influenza researchers.  The review pointed out that industry funded research came to more positive conclusions about the vaccines than independent research.

Other choice bits of the review include:  “In specific cases, influenza vaccines were associated with serious harms such as narcolepsy and febrile convulsions. It was surprising to find only one study of inactivated vaccine in children under two years, given current recommendations to vaccinate healthy children from six months of age in the USA, Canada, parts of Europe and Australia. If immunisation in children is to be recommended as a public health policy, large-scale studies assessing important outcomes, and directly comparing vaccine types are urgently required.”

When we switch to the Lancet meta-analysis from September of 2012 (complete abstract below), they have this to say about influenza research: “Efficacy of TIV (trivalent inactivated vaccine) was shown in eight (67%) of the 12 seasons analysed in ten randomized controlled trials (pooled efficacy 59% [95% CI 51-67] in adults aged 18-65 years). No such trials met inclusion criteria for children aged 2-17 years or adults aged 65 years or older.”

To be exact (Lancet quote): “Influenza vaccines can provide moderate protection against virologically confirmed influenza, but such protection is greatly reduced or absent in some seasons. Evidence for protection in adults aged 65 years or older is lacking.”

But who cares about the rest of the world.  What’s happening here in Maine?  Fortunately we’ve had two studies of the influenza vaccine here in Maine in the last couple of years.  The results?  Maine is on par “after adjusting for a diagnosis of asthma, 1 dose of 2009 H1N1 vaccine provided 69% protection.”

So how does that increased protection show up in dollars and cents?  How much less absenteeism did we see as a result of vaccination?  Here’s the quote:  “as immunization coverage during the peak week of pandemic virus circulation increased from 38% to 69% (the 10th and 90th percentiles of observed coverage, respectively), relative reductions in daily absenteeism among all students, unimmunized students, and teachers were 8.2% (95% confidence interval [CI]: 6.5, 9.9), 5.7% (95% CI: 4.2, 7.3), and 8.7% (95% CI: 1.3, 16), respectively. Increased vaccination coverage among school-aged Maine children had modest overall and indirect effects on student and teacher absenteeism.”  In other words, we doubled our vaccinations during peak season, and really didn’t see that much difference in absenteeism.  Mind you, these aren’t decreases in severe side effects from influenza (like that six-year-old who died and we keep having mentioned over and over and over in every newscast).  What does the vaccine do for those severe side effects?  Here’s the Cochrane meta-analysis:  “no evidence of effect on secondary cases, lower respiratory tract disease, drug prescriptions, otitis media and its consequences and socioeconomic impact.”

So to paraphrase the experts, the vaccine might help prevent you from getting the flu, but not for many subgroups, which haven’t been studied.  We have no evidence that the vaccine will prevent you from getting secondary infections and dying.  This year’s vaccine doesn’t seem to be a particularly good match for the circulating viruses.  So make your own decision.

For other things to do besides getting the vaccine, check out: http://www.maloneymedical.com/id90.html

 

Here are the abstracts (for the geeks among us who just need their data hit direct):

MMWR Morb Mortal Wkly Rep. 2013 Jan 18;62:32-5.

Early estimates of seasonal influenza vaccine effectiveness – United States, january 2013.

Centers for Disease Control and Prevention (CDC).

Abstract

In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months. Each season since 2004-05, CDC has estimated the effectiveness of seasonal influenza vaccine to prevent influenza-associated, medically attended acute respiratory infection (ARI). This season, early data from 1,155 children and adults with ARI enrolled during December 3, 2012-January 2, 2013 were used to estimate the overall effectiveness of seasonal influenza vaccine for preventing laboratory-confirmed influenza virus infection associated with medically attended ARI. After adjustment for study site, but not for other factors, the estimated vaccine effectiveness (VE) was 62% (95% confidence intervals [CIs] = 51%-71%). This interim estimate indicates moderate effectiveness, and is similar to a summary VE estimate from a meta-analysis of randomized controlled clinical trial data; final estimates likely will differ slightly. As of January 11, 2013, 24 states and New York City were reporting high levels of influenza-like illness, 16 states were reporting moderate levels, five states were reporting low levels, and one state was reporting minimal levels. CDC and the Advisory Committee on Immunization Practices routinely recommend that annual influenza vaccination efforts continue as long as influenza viruses are circulating. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated. However, these early VE estimates underscore that some vaccinated persons will become infected with influenza; therefore, antiviral medications should be used as recommended for treatment in patients, regardless of vaccination status. In addition, these results highlight the importance of continued efforts to develop more effective vaccines.

PMID: 23325354

Cochrane Database Syst Rev. 2012 Aug 15;8:CD004879. doi: 10.1002/14651858.CD004879.pub4.

Vaccines for preventing influenza in healthy children.

Jefferson T, Rivetti A, Di Pietrantonj C, Demicheli V, Ferroni E.

Source

The Cochrane Collaboration, Roma, Italy. jefferson.tom@gmail.com

Abstract

BACKGROUND:

The consequences of influenza in children and adults are mainly absenteeism from school and work. However, the risk of complications is greatest in children and people over 65 years of age.

OBJECTIVES:

To appraise all comparative studies evaluating the effects of influenza vaccines in healthy children, assess vaccine efficacy (prevention of confirmed influenza) and effectiveness (prevention of influenza-like illness (ILI)) and document adverse events associated with influenza vaccines.

SEARCH METHODS:

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 3) which includes the Acute Respiratory Infections Group’s Specialised Register, OLD MEDLINE (1950 to 1965), MEDLINE (1966 to November 2011), EMBASE (1974 to November 2011), Biological Abstracts (1969 to September 2007), and Science Citation Index (1974 to September 2007).

SELECTION CRITERIA:

Randomised controlled trials (RCTs), cohort and case-control studies of any influenza vaccine in healthy children under 16 years of age.

DATA COLLECTION AND ANALYSIS:

Four review authors independently assessed trial quality and extracted data.

MAIN RESULTS:

We included 75 studies with about 300,000 observations. We included 17 RCTs, 19 cohort studies and 11 case-control studies in the analysis of vaccine efficacy and effectiveness. Evidence from RCTs shows that six children under the age of six need to be vaccinated with live attenuated vaccine to prevent one case of influenza (infection and symptoms). We could find no usable data for those aged two years or younger.Inactivated vaccines in children aged two years or younger are not significantly more efficacious than placebo. Twenty-eight children over the age of six need to be vaccinated to prevent one case of influenza (infection and symptoms). Eight need to be vaccinated to prevent one case of influenza-like-illness (ILI). We could find no evidence of effect on secondary cases, lower respiratory tract disease, drug prescriptions, otitis media and its consequences and socioeconomic impact. We found weak single-study evidence of effect on school absenteeism by children and caring parents from work. Variability in study design and presentation of data was such that a meta-analysis of safety outcome data was not feasible. Extensive evidence of reporting bias of safety outcomes from trials of live attenuated influenza vaccines (LAIVs) impeded meaningful analysis. One specific brand of monovalent pandemic vaccine is associated with cataplexy and narcolepsy in children and there is sparse evidence of serious harms (such as febrile convulsions) in specific situations.

AUTHORS’ CONCLUSIONS:

Influenza vaccines are efficacious in preventing cases of influenza in children older than two years of age, but little evidence is available for children younger than two years of age. There was a difference between vaccine efficacy and effectiveness, partly due to differing datasets, settings and viral circulation patterns. No safety comparisons could be carried out, emphasising the need for standardisation of methods and presentation of vaccine safety data in future studies. In specific cases, influenza vaccines were associated with serious harms such as narcolepsy and febrile convulsions. It was surprising to find only one study of inactivated vaccine in children under two years, given current recommendations to vaccinate healthy children from six months of age in the USA, Canada, parts of Europe and Australia. If immunisation in children is to be recommended as a public health policy, large-scale studies assessing important outcomes, and directly comparing vaccine types are urgently required. The degree of scrutiny needed to identify all global cases of potential harms is beyond the resources of this review. This review includes trials funded by industry. 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 favourable 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 the light of this finding.

Update of

Cochrane Database Syst Rev. 2008;(2):CD004879.

PMID: 22895945

Lancet Infect Dis. 2012 Jan;12(1):36-44. doi: 10.1016/S1473-3099(11)70295-X. Epub 2011 Oct 25.

Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis.

Osterholm MT, Kelley NS, Sommer A, Belongia EA.

Source

Center for Infectious Disease Research and Policy, University of Minnesota, MN 55455, USA. mto@umn.edu

Erratum in

Lancet Infect Dis. 2012 Sep;12(9):655.

Abstract

BACKGROUND:

No published meta-analyses have assessed efficacy and effectiveness of licensed influenza vaccines in the USA with sensitive and highly specific diagnostic tests to confirm influenza.

METHODS:

We searched Medline for randomised controlled trials assessing a relative reduction in influenza risk of all circulating influenza viruses during individual seasons after vaccination (efficacy) and observational studies meeting inclusion criteria (effectiveness). Eligible articles were published between Jan 1, 1967, and Feb 15, 2011, and used RT-PCR or culture for confirmation of influenza. We excluded some studies on the basis of study design and vaccine characteristics. We estimated random-effects pooled efficacy for trivalent inactivated vaccine (TIV) and live attenuated influenza vaccine (LAIV) when data were available for statistical analysis (eg, at least three studies that assessed comparable age groups).

FINDINGS:

We screened 5707 articles and identified 31 eligible studies (17 randomised controlled trials and 14 observational studies). Efficacy of TIV was shown in eight (67%) of the 12 seasons analysed in ten randomised controlled trials (pooled efficacy 59% [95% CI 51-67] in adults aged 18-65 years). No such trials met inclusion criteria for children aged 2-17 years or adults aged 65 years or older. Efficacy of LAIV was shown in nine (75%) of the 12 seasons analysed in ten randomised controlled trials (pooled efficacy 83% [69-91]) in children aged 6 months to 7 years. No such trials met inclusion criteria for children aged 8-17 years. Vaccine effectiveness was variable for seasonal influenza: six (35%) of 17 analyses in nine studies showed significant protection against medically attended influenza in the outpatient or inpatient setting. Median monovalent pandemic H1N1 vaccine effectiveness in five observational studies was 69% (range 60-93).

INTERPRETATION:

Influenza vaccines can provide moderate protection against virologically confirmed influenza, but such protection is greatly reduced or absent in some seasons. Evidence for protection in adults aged 65 years or older is lacking. LAIVs consistently show highest efficacy in young children (aged 6 months to 7 years). New vaccines with improved clinical efficacy and effectiveness are needed to further reduce influenza-related morbidity and mortality.

FUNDING:

Alfred P Sloan Foundation.

Copyright © 2012 Elsevier Ltd. All rights reserved.

Comment in

Estimating the effect of influenza vaccines. [Lancet Infect Dis. 2012]

Review: flu vaccines provide a moderate risk reduction in healthy children. [Arch Dis Child Educ Pract Ed. 2012]

Quantifying the efficacy of influenza vaccines. [Lancet Infect Dis. 2012]

Quantifying the efficacy of influenza vaccines. [Lancet Infect Dis. 2012]

Quantifying the efficacy of influenza vaccines. [Lancet Infect Dis. 2012]

Quantifying the efficacy of influenza vaccines. [Lancet Infect Dis. 2012]

Quantifying the efficacy of influenza vaccines. [Lancet Infect Dis. 2012]

PMID: 22032844

PLoS One. 2011;6(8):e23085. doi: 10.1371/journal.pone.0023085. Epub 2011 Aug 12.

Effectiveness of non-adjuvanted pandemic influenza A vaccines for preventing pandemic influenza acute respiratory illness visits in 4 U.S. communities.

Griffin MR, Monto AS, Belongia EA, Treanor JJ, Chen Q, Chen J, Talbot HK, Ohmit SE, Coleman LA, Lofthus G, Petrie JG, Meece JK, Hall CB, Williams JV, Gargiullo P, Berman L, Shay DK; U.S. Flu-VE Network.

Collaborators (36)

Source

Department of Preventive Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America. marie.griffin@vanderbilt.edu

Abstract

We estimated the effectiveness of four monovalent pandemic influenza A (H1N1) vaccines (three unadjuvanted inactivated, one live attenuated) available in the U.S. during the pandemic. Patients with acute respiratory illness presenting to inpatient and outpatient facilities affiliated with four collaborating institutions were prospectively recruited, consented, and tested for influenza. Analyses were restricted to October 2009 through April 2010, when pandemic vaccine was available. Patients testing positive for pandemic influenza by real-time RT-PCR were cases; those testing negative were controls. Vaccine effectiveness was estimated in logistic regression models adjusted for study community, patient age, timing of illness, insurance status, enrollment site, and presence of high-risk medical conditions. Pandemic virus was detected in 1,011 (15%) of 6,757 enrolled patients. Fifteen (1%) of 1,011 influenza positive cases and 1,042 (18%) of 5,746 test-negative controls had record-verified pandemic vaccination >14 days prior to illness onset. Adjusted effectiveness (95% confidence interval) for pandemic vaccines combined was 56% (23%, 75%). Adjusted effectiveness for inactivated vaccines alone (79% of total) was 62% (25%, 81%) overall and 32% (-92%, 76%), 89% (15%, 99%), and -6% (-231%, 66%) in those aged 0.5 to 9, 10 to 49, and 50+ years, respectively. Effectiveness for the live attenuated vaccine in those aged 2 to 49 years was only demonstrated if vaccination >7 rather than >14 days prior to illness onset was considered (61%∶ 12%, 82%). Inactivated non-adjuvanted pandemic vaccines offered significant protection against confirmed pandemic influenza-associated medical care visits in young adults.

PMID: 21857999

J Infect Dis. 2012 Oct 1;206(7):1059-68. Epub 2012 Jul 30.

Effectiveness of 1 dose of influenza A (H1N1) 2009 monovalent vaccines in preventing reverse-transcription polymerase chain reaction-confirmed H1N1 infection among school-aged children in maine.

Uzicanin A, Thompson M, Smith P, Chaves SS, Foster L, Dube N, Graitcer S, Jackson R, Ferdinands J, Gargiullo P, Mills D, Monto AS, Shay DK; Maine 2009 Influenza A (H1N1) Vaccine Effectiveness Evaluation Group.

Collaborators (21)

Source

Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. aau5@cdc.gov

Abstract

BACKGROUND:

In late October 2009, school-located pandemic vaccination was initiated in Maine before or concurrent with 2009 pandemic influenza A (H1N1) virus (pH1N1) peak activity.

METHODS:

A case-control evaluation of 2009 H1N1 vaccine effectiveness was conducted in schools in Cumberland County, Maine. A case was a child who had an acute respiratory illness during 2 November-18 December 2009, and who tested positive for pH1N1 by real-time reverse-transcription polymerase chain reaction (rRT-PCR). For each case, ≥ 4 event time-matched controls were sampled among classmates present in school during the study period who did not have an influenza-like illness. Vaccine effectiveness was calculated as (1 – adjusted odds ratio [aOR])100%; aOR was estimated by using weighted logistic regression.

RESULTS:

After adjusting for a diagnosis of asthma, 1 dose of 2009 H1N1 vaccine provided 69% protection (95% confidence interval (CI), 13-89) against rRT-PCR-confirmed H1N1 infection. Vaccine effectiveness estimates for live attenuated and inactivated vaccine were 81% (95% CI, -37 to 97), and 58% (95% CI: -39 to 87), respectively. Conclusions: One dose of monovalent pandemic vaccine provided substantial protection against pH1N1 infection among school-aged children.

PMID: 22850120

Vaccine. 2012 Jul 6;30(32):4835-41. doi: 10.1016/j.vaccine.2012.05.008. Epub 2012 May 17.

Effects of immunizing school children with 2009 influenza A (H1N1) monovalent vaccine on absenteeism among students and teachers in Maine.

Graitcer SB, Dube NL, Basurto-Davila R, Smith PF, Ferdinands J, Thompson M, Uzicanin A, Gargiullo P, Chaves SS, Robinson S, Sears S, Tipton M, Monto AS, Mills D, Shay DK.

Source

Epidemic Intelligence Service, Assigned to Influenza Division (Now with Immunization Services Division), Centers for Disease Control and Prevention, Mailstop A-19, Atlanta, GA 30333, United States. SGraitcer@cdc.gov

Abstract

The overall and indirect effects of immunizing school children with influenza A (H1N1) 2009 pandemic virus vaccine prior to and during the peak of virus circulation were evaluated on student and teacher school absenteeism. We used records collected from late 2009 through early 2010 from schools in four Maine counties. Mixed logistic regression models were used to estimate the daily association between school-level immunization coverage and absenteeism by level of influenza activity, after adjusting for the proportion of students receiving reduced-cost lunches, student minority status, absences adjacent to weekends and Thanksgiving, rural school location, and the circulation of other respiratory viruses. Increasing student immunization coverage was associated with reduced absenteeism during periods of high influenza activity. For example, as immunization coverage during the peak week of pandemic virus circulation increased from 38% to 69% (the 10th and 90th percentiles of observed coverage, respectively), relative reductions in daily absenteeism among all students, unimmunized students, and teachers were 8.2% (95% confidence interval [CI]: 6.5, 9.9), 5.7% (95% CI: 4.2, 7.3), and 8.7% (95% CI: 1.3, 16), respectively. Increased vaccination coverage among school-aged Maine children had modest overall and indirect effects on student and teacher absenteeism, despite vaccination occurring just prior and during peak pandemic virus circulation.

Published by Elsevier Ltd.

PMID: 22609012

MMWR Morb Mortal Wkly Rep. 2012 Apr 6;61(13):229-32.

Influenza outbreaks at two correctional facilities — Maine, March 2011.

Centers for Disease Control and Prevention (CDC).

Abstract

On March 8, 2011, the Maine Center for Disease Control and Prevention (Maine CDC) received a laboratory report of a positive influenza specimen from an intensive-care unit patient who was an inmate at a prison (facility A). That same day, the state medical examiner notified Maine CDC of an inmate death suspected to be have been caused by influenza at another, nearby prison (facility B). On March 9, Correctional Medical Services (CMS), which provides health services to both facilities, notified Maine CDC that additional inmates and staff members from both facilities were ill with influenza-like illness (ILI). CMS reported that influenza vaccination coverage among inmates was very low (<10%), and coverage among staff members was unknown but believed to be low. Maine CDC assisted CMS and the Maine Department of Corrections (DOC) in conducting an epidemiologic investigation to gather more information about the two cases, initiate case finding, and implement control measures, which included emphasizing respiratory hygiene and cough etiquette, closing both facilities to new admissions and transfers, and offering vaccination and antiviral drugs to inmates and staff members. This report describes the public health response and highlights the importance of collaboration between public health and corrections officials to identify quickly and mitigate communicable disease outbreaks in these settings, where influenza can spread rapidly in a large and concentrated population. Correctional facilities should strongly consider implementing the following measures during each influenza season: 1) offering influenza vaccination to all inmates and staff members, 2) conducting education on respiratory etiquette, and 3) making documentation regarding the vaccination status of inmates and staff members accessible.

PMID: 22475851


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