Notices
Results 1 to 7 of 7

Thread: Interpreting meaning in influenza vaccination study results

  1. #1 Interpreting meaning in influenza vaccination study results 
    Forum Freshman
    Join Date
    Feb 2013
    Posts
    7
    Here is the study: Evidence of bias in estimates of influenza vaccine effectiveness in seniors

    The authors hypothesis is that those who get the influenza vaccination are more likely to be heath conscious individuals which might account for lower incidence of infection.

    I am having some issues interpreting how the results of the authors statistical analysis correlates with the conclusions. Correct me if I'm wrong, but from what I can tell, as progression through the influenza season ensues the relationship between healthy and unhealthy individuals (as established in the study) has a tendency to approach 1. I'm not sure how that correlates with a potential bias. Please explain.

    Some other confusing issues:

    How is the relationship number established and what factors make it change with time?

    Why is it that "healthy individuals" represent a demographic with more comorbidities? Isn't the reverse true? Perhaps I'm misinterpreting the data.


    Reply With Quote  
     

  2.  
     

  3. #2  
    Moderator Moderator
    Join Date
    Nov 2011
    Location
    city of wine and roses
    Posts
    6,225
    Why is it that "healthy individuals" represent a demographic with more comorbidities?
    If I'm reading this aright, the population in question is seniors. That demographic always has more comorbidities, regardless of the health issue under examination.


    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
    Reply With Quote  
     

  4. #3  
    Forum Freshman
    Join Date
    Feb 2013
    Posts
    7
    Quote Originally Posted by adelady View Post
    Why is it that "healthy individuals" represent a demographic with more comorbidities?
    If I'm reading this aright, the population in question is seniors. That demographic always has more comorbidities, regardless of the health issue under examination.
    Correct. My confusion in regards to this specific question comes from Table 2 on page 340. I interpret this data to read that the vaccinated older adults consistently have a higher probability of having a given co-morbidity when compared to the unvaccinated older adult. This data seems counter intuitive and contrary to the authors conclusion statement made in the abstract "The reductions in risk before influenza season indicate preferential receipt of vaccine by relatively healthy seniors."

    The authors premise is that health conscious older adults are more likely to get vaccinated (than less health conscious older adults), resulting in prophylactic bias in the data, as these individuals are less likely to get sick in the first place. The fact that the data shows those elders who get vaccinated actually have more co-morbidities than elders who do not get vaccinated would deem the vaccinated group as less healthy would it not?
    Reply With Quote  
     

  5. #4  
    Forum Freshman
    Join Date
    Feb 2013
    Posts
    7
    Perhaps someone who is more statistically inclined than myself can help by explaining the meaning of the results:

    Results: The relative risk of death for vaccinated persons compared with unvaccinated
    persons was 0.39 [95% confidence interval (95% CI), 0.33–0.47] before influenza
    season, 0.56 (0.52–0.61) during influenza season, and 0.74 (0.67–0.80) after
    influenza season. The relative risk of pneumonia hospitalization was 0.72
    (0.59–0.89) before, 0.82 (0.75–0.89) during, and 0.95 (0.85–1.07) after influenza
    season. Adjustment for diagnosis code variables resulted in estimates that were
    further from the null, in all time periods.


    What is the meaning of the numbers 0.39, 0.56, 0.72 etc.?

    How did these numbers come to be?

    Lastly, what does it mean that they consistently show the tendency to approach 1 with the progression of time? (see also table 5 on page 342)


    Kind Regards
    Last edited by DBecker1988; February 15th, 2013 at 09:03 PM.
    Reply With Quote  
     

  6. #5  
    Moderator Moderator
    Join Date
    Nov 2011
    Location
    city of wine and roses
    Posts
    6,225
    The fact that the data shows those elders who get vaccinated actually have more co-morbidities than elders who do not get vaccinated would deem the vaccinated group as less healthy would it not?
    Well, sick people see their doctors more often and they'd be first cabs off the rank in getting vaccinated, the doctors would make sure of it even if the patients didn't think of it for themselves. So you'd get near total coverage for those people.

    If you remember the advertisements for vaccination campaigns, they focus on certain illnesses and conditions, and they mention 'age over 60 or 65'. A lot of healthy older people don't like to think of themselves as aged, let alone vulnerable. So they skip some years, or every year. Or they mean to get around to it but never have a particular reason to go to a doctor or a clinic, so they forget about it until they suddenly realise that flu season is nearly over - or they get sick with it and vaccination is too late.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
    Reply With Quote  
     

  7. #6  
    Forum Professor arKane's Avatar
    Join Date
    Apr 2009
    Location
    Washington state
    Posts
    1,181
    Quote Originally Posted by adelady View Post
    The fact that the data shows those elders who get vaccinated actually have more co-morbidities than elders who do not get vaccinated would deem the vaccinated group as less healthy would it not?
    Well, sick people see their doctors more often and they'd be first cabs off the rank in getting vaccinated, the doctors would make sure of it even if the patients didn't think of it for themselves. So you'd get near total coverage for those people.

    If you remember the advertisements for vaccination campaigns, they focus on certain illnesses and conditions, and they mention 'age over 60 or 65'. A lot of healthy older people don't like to think of themselves as aged, let alone vulnerable. So they skip some years, or every year. Or they mean to get around to it but never have a particular reason to go to a doctor or a clinic, so they forget about it until they suddenly realize that flu season is nearly over - or they get sick with it and vaccination is too late.
    That sounds as good as anything I've heard. I might have skiped getting vaccinated this year had not my doctor pushed the issue with me. When you reach 65 They recommend a flu shot every year and your first pneumonia vaccination. Flu shot's don't guarantee you won't get the flu, however the affect of it should be considerably lessened if you do get it, and the pneumonia shot will lessen the chance of a secondary common lung infection. Most adults get the flu when they are around people with a high probability of being infected. They bring it home from work or their kids bring it home and give it to the parents. I don't go to work and rarely come into contact with kids. My chance of being exposed is very low and I have my shots for those rare occasions when I might be exposed, so I don't expect to get the flu. I have had very bad cases of flu when I was younger and don't need that experience ever again. So I consider the shots worth it.
    Reply With Quote  
     

  8. #7  
    Forum Freshman
    Join Date
    Feb 2013
    Posts
    7
    Your analysis correctly accounts for the statistical differences between the two groups. The issue is that the author makes no mention of this, but rather concludes that the vaccinated group is the healthier group. The data says differently and this is one of the issues I am having. Why did the author come to this conclusion?

    The first sentence of the discussion section reads:

    "In this study, the reductions in risk observed in the before influenza period suggest the presence of bias due to preferential receipt of vaccine by relatively healthy seniors on the estimates of influenza vaccine effectiveness observed during influenza season."


    The argument the author is trying to make is that healthy elders are motivated to be healthy and make healthy choices such as eating right, exercising, and getting their yearly vaccination. From this notion the author hypothesis that the main reason they are less likely to get sick is not from the vaccination, but rather from the other measures these people are taking to be healthy (exercise and diet). The author then supposedly shows this idea to be true from statistical analysis (which I don't understand).

    From what I can tell the authors argument is flawed related to your discussion in post #5. I'm also suspect of the statistical analysis, but need clarification regarding this matter before I can comment.
    Reply With Quote  
     

Similar Threads

  1. Need help Interpreting a Graph
    By chrisman10 in forum Earth Sciences
    Replies: 31
    Last Post: February 24th, 2013, 05:47 PM
  2. Influenza: A Laymans Explanation, Please!
    By Guvna in forum Biology
    Replies: 2
    Last Post: September 13th, 2009, 05:49 PM
  3. HPV vaccination for males
    By i_feel_tiredsleepy in forum Health & Medicine
    Replies: 15
    Last Post: March 23rd, 2009, 05:01 PM
  4. Vaccination, is it really worth it?
    By timel in forum Biology
    Replies: 17
    Last Post: October 7th, 2008, 03:58 AM
  5. Replies: 0
    Last Post: July 27th, 2008, 04:12 PM
Tags for this Thread

View Tag Cloud

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •