Wednesday, November 7, 2012

Should I Get A Flu Shot?


It's that time of year again. Everyone seems to be advertising the flu vaccine. Your doctor, your local hospital, walk-in clinics, and even the local pharmacy all have the flu vaccine ready and waiting for you to get vaccinated. But, should you get it? I'm not going to tell you either way. What I will do is supply you with the evidence from a number of comprehensive reviews on the scientific and medical literature done on the flu vaccine. This way you can make an informed decision on your own on whether or not to get the flu shot.

As a clinical pharmacist, I'm just as interested as you are on whether or not the flu shot is worth getting. For this reason, I did what any respective healthcare professional would do. I turned to the Cochrane Collaboration for answers.

The Cochrane Collaboration is a non-profit, international network of over 28,000 individuals from over 100 countries. These individuals work to provide unbiased, evidence-based reviews from available scientific and medical research studies to help healthcare providers, policy-makers, patients and their advocates make informed decisions regarding their health care. These reviews are called the Cochrane Reviews. These reviews are highly trusted and credible because they are free of commercial bias. The Cochrane Collaboration doesn't allow big money or special interest groups to taint their organization or their highly respected work. This is made evident in their commercial sponsorship policy:

"The Cochrane Collaboration has gained an international reputation for producing evidence of the highest standard to inform healthcare decision-making. To maintain this reputation, we are committed to ensuring that the results of Cochrane Reviews are not influenced by personal or commercial interests, particularly from the pharmaceutical industry and medical device manufacturers. Sponsorship of Cochrane Reviews, their derivative products, author teams and the Cochrane 'entities' who produce them, by any commercial source, is strictly prohibited."


This doesn't mean that the Cochrane Collaboration avoids reviewing studies that are funded by drug companies or medical device companies. It only means they, as an organization, provide unbiased reviews based on ALL the available data whether or not it was industry funded, government funded, or privately funded. They do an excellent job in reporting whether or not studies reviewed by their organization were funded (and ultimately biased) by industry or not.

Below are the conclusions from the Cochrane Collaboration on the use of influenza vaccinations in different segments of the human population.

Flu Vaccines To Prevent Influenza In Healthy Adults


"Over 200 viruses cause influenza and influenza-like illness which produce the same symptoms (fever, headache, aches and pains, cough and runny noses). Without laboratory tests, doctors cannot tell the two illnesses apart. Both last for days and rarely lead to death or serious illness. At best, vaccines might be effective against only influenza A and B, which represent about 10% of all circulating viruses. Each year, the World Health Organization recommends which viral strains should be included in vaccinations for the forthcoming season.

Authors of this review assessed all trials that compared vaccinated people with unvaccinated people. The combined results of these trials showed that under ideal conditions (vaccine completely matching circulating viral configuration) 33 healthy adults need to be vaccinated to avoid one set of influenza symptoms. In average conditions (partially matching vaccine) 100 people need to be vaccinated to avoid one set of influenza symptoms. Vaccine use did not affect the number of people hospitalised or working days lost but caused one case of Guillian-Barré syndrome (a major neurological condition leading to paralysis) for every one million vaccinations. Fifteen of the 36 trials were funded by vaccine companies and four had no funding declaration. Our results may be an optimistic estimate because company-sponsored influenza vaccines trials tend to produce results favorable to their products and some of the evidence comes from trials carried out in ideal viral circulation and matching conditions and because the harms evidence base is limited.

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."

Reviewing the main points:
  1. At best, the flu vaccine covers approximately 10% of the 200 or more viruses that may cause the flu.
  2. For the average, healthy everyday person a total of 1 case of influenza was prevented for every 100 persons vaccinated.
  3. Flu vaccine use did not affect total number of people hospitalized from the disease.
  4. Flu vaccine use did not reduce total number of working days lost (sick days) due to the flu.
  5. There is a one in a million chance those vaccinated could develop Guillan-Barré syndrome (serious neurological condition leading to paralysis).
  6. The most highly publicized studies in the most prestigious medical journals are funded by industry (aka drug companies) and produce more favorable outcomes, while publicly funded (aka government funded) studies reported less favorable outcomes for getting the flu vaccine.

Flu Vaccines To Prevent Influenza In People Aged 65 And Older


"Influenza vaccination of elderly individuals is recommended worldwide as people aged 65 and older are at a higher risk of complications, hospitalisations and deaths from influenza. This review looked at evidence from experimental and non-experimental studies carried out over 40 years of influenza vaccination. We included 75 studies. These were grouped first according to study design and then the setting (community or long-term care facilities). The results are mostly based on non-experimental (observational) studies, which are at greater risk of bias, as not many good quality trials were available. Trivalent inactivated vaccines are the most commonly used influenza vaccines. Due to the poor quality of the available evidence, any conclusions regarding the effects of influenza vaccines for people aged 65 years or older cannot be drawn. The public health safety profile of the vaccines appears to be acceptable.

The available evidence is of poor quality and provides no guidance regarding the safety, efficacy or effectiveness of influenza vaccines for people aged 65 years or older. To resolve the uncertainty, an adequately powered publicly-funded randomised, placebo-controlled trial run over several seasons should be undertaken."

Reviewing the main points:
  1. Individuals over the age of 65 are at higher risk of complications (hospitalizations and death) from getting the flu.
  2. Data spanning a 40 year period and including 75 studies were of poor quality and no conclusions could be drawn on recommendations regarding the safety and efficacy of the flu vaccine in the elderly.


"Children (less than 16 years old) and the elderly (above 65 years old) are the two age groups that appear to have the most complications following an influenza infection. Influenza has a viral origin and often results in an acute respiratory illness affecting the lower or upper parts of the respiratory tract, or both. Viruses are mainly of two subtypes (A or B) and spread periodically during the autumn-winter months. However, many other viruses can also cause respiratory tract illnesses.

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).

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."

Reviewing the main points:

  1. Flu vaccines are no better than placebo in children aged 2 and younger.
  2. One case of influenza is prevented for every 6 children vaccinated in children aged 2-6 years old.
  3. One case of influenza is prevented for every 28 children vaccinated in children aged 6 and over.
  4. One case of "flu-like" illness is prevented for every 8 children vaccinated in children 6 and over.
  5. Cases of narcolepsy and febrile seizures have been associated with the administration of flu vaccines in children.
  6. The most highly publicized studies in the most prestigious medical journals are funded by industry (aka drug companies) and produce more favorable outcomes, while publicly funded (aka government funded) studies reported less favorable outcomes for getting the flu vaccine.


"Older individuals in long-term care institutions (LTCIs) at risk of influenza may be infected by their healthcare workers. There are no accurate data on rates of laboratory-proven influenza in healthcare workers. Vaccinating healthcare workers against influenza may reduce infections acquired from this source. Because the signs and symptoms of influenza are similar to those of many other respiratory illnesses, it is important in studies testing the effects of influenza vaccination to prove by laboratory tests which are highly accurate whether residents in LTCIs actually have influenza or another respiratory illness.

This review did not find information on other interventions used in conjunction with vaccinating healthcare workers (hand-washing, face masks, early detection of laboratory-proven influenza, quarantine, avoiding new admissions, prompt use of antivirals and asking healthcare workers with an influenza-like illness not to work.)

There is no evidence that only vaccinating healthcare workers prevents laboratory-proven influenza or its complications (lower respiratory tract infection, hospitalisation or death due to lower respiratory tract infection) in individuals aged 60 or over in LTCIs and thus no evidence to mandate compulsory vaccination of healthcare workers. Other interventions, such as hand-washing, masks, early detection of influenza with nasal swabs, antivirals, quarantine, restricting visitors and asking healthcare workers with an influenza-like illness not to attend work, might protect individuals over 60 in LTCIs. High-quality randomised controlled trials testing combinations of these interventions are needed.

The results for specific outcomes: laboratory-proven influenza or its complications (lower respiratory tract infection, or hospitalisation or death due to lower respiratory tract illness) did not identify a benefit of healthcare worker vaccination on these key outcomes. This review did not find information on co-interventions with healthcare worker vaccination: hand-washing, face masks, early detection of laboratory-proven influenza, quarantine, avoiding admissions, antivirals and asking healthcare workers with influenza or influenza-like-illness (ILI) not to work. This review does not provide reasonable evidence to support the vaccination of healthcare workers to prevent influenza in those aged 60 years or older resident in LTCIs. High-quality RCTs are required to avoid the risks of bias in methodology and conduct identified by this review and to test further these interventions in combination."

Reviewing the main points:

  1. All available studies on flu vaccinations in healthcare workers were found by Cochrane reviewers to have some risk of bias. Please read actual review for bias potential.
  2. No conclusive evidence could be found that vaccinating healthcare workers prevents cases of flu or pneumonia illnesses in elderly residents of long term care facilities based on positively confirmed laboratory tests.
  3. Other common sense approaches (hand washing, wearing masks, quarantining sick patients, restricting visitors, staying home from work when sick, etc.) may be more useful in preventing flu-like illnesses in the elderly in long-term care settings.

Summary


Should you get the flu vaccine or not? That's completely up to you. You now have the evidence needed to make an informed healthcare decision. Regardless of whether or not you get the flu shot, I would encourage you to focus on some simple everyday habits to improve your ability to fight off infections (watch video below). These habits include eating a health promoting, plant-based diet and staying physically active. Both are vital tools to remaining in good health. For you and your family's sake, I hope the cold and flu season doesn't get the best of you. May you and your loved ones have a happy and healthy holiday season. Thank you for visiting my site.








Photo credits: Freedigitalphotos.net

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by Dustin Rudolph, PharmD
Clinical Pharmacist

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