Randomised Control Trials: Vaccines Flashcards
MMR vaccine report
- “Intestinal and behavioural pathologies may have occurred together by chance, reflecting a selection bias in a self-referred group; however, the uniformity of the intestinal pathological changes and the fact that previous studies have intestinal dysfunction in children with autistic-spectrum disorders, suggests that the connection is real and reflects a unique disease process.”
- Report suggested causal link between autism and MMR, wakefield said to stop in favour of MMR - still causes issues today
- What has happened since? - what is the issue with this?
- Was retracted
- Confounding !!
Confounding – when we mix up causes
- What is missing?
ANOTHER FACTOR
Confounding
- Additional issues in the Wakefield study:-
- Children selected because their mothers believed they had …-related health problems
- Two of the children:
- were …
- with long-standing recognised histories of … and bowel problems
- the mother was a member of an anti-vaxxers group
- A further child was put forward by the brothers’ mother and this child’s mother encouraged to participate
- Issues with the diagnosis of ‘inflammatory bowel disease’
- Additional issues in the Wakefield study:-
- Children selected because their mothers believed they had vaccine-related health problems
- Two of the children:
- were brothers
- with long-standing recognised histories of autism and bowel problems
- the mother was a member of an anti-vaxxers group
- A further child was put forward by the brothers’ mother and this child’s mother encouraged to participate
- Issues with the diagnosis of ‘inflammatory bowel disease’
Confounding
- Additional issues in the … study:-
- Children selected because their mothers believed they had vaccine-related health problems
- Two of the children:
- were brothers
- with long-standing recognised histories of autism and bowel problems
- the mother was a member of an … group
- A further child was put forward by the brothers’ mother and this child’s mother encouraged to participate
- Issues with the diagnosis of ‘inflammatory bowel disease’
- Additional issues in the Wakefield study:-
- Children selected because their mothers believed they had vaccine-related health problems
- Two of the children:
- were brothers
- with long-standing recognised histories of autism and bowel problems
- the mother was a member of an anti-vaxxers group
- A further child was put forward by the brothers’ mother and this child’s mother encouraged to participate
- Issues with the diagnosis of ‘inflammatory bowel disease’
Confounding
- Additional issues in the Wakefield study:-
- Children selected because their mothers believed they had vaccine-related health problems
- Two of the children:
- were …
- with …-standing recognised histories of autism and … problems
- the mother was a member of an anti-vaxxers group
- A further child was put forward by the brothers’ mother and this child’s mother encouraged to participate
- Issues with the diagnosis of ‘inflammatory bowel disease’
- Additional issues in the Wakefield study:-
- Children selected because their mothers believed they had vaccine-related health problems
- Two of the children:
- were brothers
- with long-standing recognised histories of autism and bowel problems
- the mother was a member of an anti-vaxxers group
- A further child was put forward by the brothers’ mother and this child’s mother encouraged to participate
- Issues with the diagnosis of ‘inflammatory bowel disease’
Confounding
- Additional issues in the Wakefield study:-
- Children selected because their mothers believed they had vaccine-related health problems
- Two of the children:
- were brothers
- with long-standing recognised histories of autism and bowel problems
- the mother was a member of an anti-vaxxers group
- A further child was put forward by the brothers’ mother and this child’s mother encouraged to participate
- Issues with the diagnosis of ‘inflammatory bowel disease’
- Additional issues in the Wakefield study:-
- Children selected because their mothers believed they had vaccine-related health problems
- Two of the children:
- were brothers
- with long-standing recognised histories of autism and bowel problems
- the mother was a member of an anti-vaxxers group
- A further child was put forward by the brothers’ mother and this child’s mother encouraged to participate
- Issues with the diagnosis of ‘inflammatory bowel disease’
Confounding in vaccine research
- Observational studies tend to
- Identify … and … people in the population and
- compare their … outcomes
- Or compare health outcomes of population before and after … of … programme
- But people who have vaccines tend to differ from those who don’t
- People with chronic diseases are more likely to be vaccinated than people
- without chronic diseases
- People with vaccines more likely to have had previous vaccines
- Same risk factors may affect vaccine uptake and disease/adverse reaction incidence
- e.g parentaleducation,smokinginpregnancy,lowbirthweight,familyhistoryof disease, healthcare access and uptake
- Placebo / nocebo effects
- Observational studies tend to
- Identify vaccinated and non-vaccinated people in the population and
- compare their health outcomes
- Or compare health outcomes of population before and after implementation of vaccine programme
- But people who have vaccines tend to differ from those who don’t
- People with chronic diseases are more likely to be vaccinated than people
- without chronic diseases
- People with vaccines more likely to have had previous vaccines
- Same risk factors may affect vaccine uptake and disease/adverse reaction incidence
- e.g parentaleducation,smokinginpregnancy,lowbirthweight,familyhistoryof disease, healthcare access and uptake
- Placebo / nocebo effects
Confounding in vaccine research
- Observational studies tend to
- Identify vaccinated and non-vaccinated people in the population and
- compare their health outcomes
- Or compare health outcomes of population before and after implementation of vaccine programme
- But people who have … tend to … from those who don’t
- People with chronic diseases are … likely to be vaccinated than people
- without chronic diseases
- People with vaccines … likely to have had previous vaccines
- Same risk factors may affect vaccine uptake and disease/adverse reaction incidence
- e.g parentaleducation,smokinginpregnancy,lowbirthweight,familyhistoryof disease, healthcare access and uptake
- Placebo / nocebo effects
- Observational studies tend to
- Identify vaccinated and non-vaccinated people in the population and
- compare their health outcomes
- Or compare health outcomes of population before and after implementation of vaccine programme
- But people who have vaccines tend to differ from those who don’t
- People with chronic diseases are more likely to be vaccinated than people
- without chronic diseases
- People with vaccines more likely to have had previous vaccines
- Same risk factors may affect vaccine uptake and disease/adverse reaction incidence
- e.g parentaleducation,smokinginpregnancy,lowbirthweight,familyhistoryof disease, healthcare access and uptake
- Placebo / nocebo effects
Confounding in vaccine research
- Observational studies tend to
- Identify vaccinated and non-vaccinated people in the population and
- compare their health outcomes
- Or compare health outcomes of population before and after implementation of vaccine programme
- But people who have vaccines tend to differ from those who don’t
- People with chronic diseases are more likely to be vaccinated than people
- without chronic diseases
- People with vaccines more likely to have had previous vaccines
- Same … factors may affect … uptake and …/… reaction incidence
- e.g parentaleducation,smokinginpregnancy,lowbirthweight,familyhistoryof disease, healthcare access and uptake
- Placebo / nocebo effects
- Observational studies tend to
- Identify vaccinated and non-vaccinated people in the population and
- compare their health outcomes
- Or compare health outcomes of population before and after implementation of vaccine programme
- But people who have vaccines tend to differ from those who don’t
- People with chronic diseases are more likely to be vaccinated than people
- without chronic diseases
- People with vaccines more likely to have had previous vaccines
- Same risk factors may affect vaccine uptake and disease/adverse reaction incidence
- e.g parentaleducation,smokinginpregnancy,lowbirthweight,familyhistoryof disease, healthcare access and uptake
- Placebo / nocebo effects
Confounding in vaccine research
- Observational studies tend to
- Identify vaccinated and non-vaccinated people in the population and
- compare their … outcomes
- Or compare … outcomes of population before and after implementation of vaccine programme
- But people who have vaccines tend to differ from those who don’t
- People with chronic diseases are more likely to be vaccinated than people
- without chronic diseases
- People with vaccines more likely to have had previous vaccines
- Same risk factors may affect vaccine uptake and disease/adverse reaction incidence
- e.g parentaleducation,smokinginpregnancy,lowbirthweight,familyhistoryof disease, healthcare access and uptake
- … / … effects
- Observational studies tend to
- Identify vaccinated and non-vaccinated people in the population and
- compare their health outcomes
- Or compare health outcomes of population before and after implementation of vaccine programme
- But people who have vaccines tend to differ from those who don’t
- People with chronic diseases are more likely to be vaccinated than people
- without chronic diseases
- People with vaccines more likely to have had previous vaccines
- Same risk factors may affect vaccine uptake and disease/adverse reaction incidence
- e.g parentaleducation,smokinginpregnancy,lowbirthweight,familyhistoryof disease, healthcare access and uptake
- Placebo / nocebo effects
Confounding across study designs
Confounding across study designs
Confounding across study designs
Confounding across study designs
Randomisation
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
Because cohort studies can be prospective, we can establish …
Because cohort studies can be prospective, we can establish temporality
Randomisation
- If random, the probability of any individual receiving one intervention or the other is decided solely by …
- So people of different levels of a … are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
Randomisation
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If … … is sufficient, all the … influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
Randomisation
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these … on the outcome of interest is then happening … within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
Randomisation
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the … rather than any other …
- If random, the probability of any individual receiving one intervention or the other is decided solely by chance
- So people of different levels of a confounder are just as likely to be allocated to each group within the study
- If sample size is sufficient, all the factors influential in the outcome are distributed equally between the groups
- Any effect of these confounders on the outcome of interest is then happening equally within each of the groups
- Therefore, any observed difference in the observed outcome between the groups is likely to be due to the intervention rather than any other factors
Confounding in vaccine research
Study - confounding
- Crude results suggest vaccine is … and … complications
- … (for confounding variables) - e.g. age, number of GP visits etc
- age, disease and GP visits make a massive difference = adjustments - vaccine … from these health outcomes
- Crude results suggest vaccine is ineffective and increase complications
- Adjustments (for confounding variables) - e.g. age, number of GP visits etc
- age, disease and GP visits make a massive difference = adjustments - vaccine protects from these health outcomes
Randomised controlled trial
Ethical and political issues in randomisation
- Ethical
- … = ethical basis for medical research that involves assigning patients to different treatments
- Clinical … = genuine uncertainty in the expert medical community over whether one treatment will be more beneficial
- It is not ethically acceptable to randomise patients to a treatment known to be inferior
- Political
- Even when there is genuine uncertainty, new intervention believed superior = non-randomised studies, waitlist controls more attractive
- Policy makers, commissioners, service leads can be unwilling to admit uncertainty
- Broader political reasons for preferring one treatment type over another
- Ethical
- Equipoise = ethical basis for medical research that involves assigning patients to different treatments
- Clinical equipoise = genuine uncertainty in the expert medical community over whether one treatment will be more beneficial
- It is not ethically acceptable to randomise patients to a treatment known to be inferior
- Political
- Even when there is genuine uncertainty, new intervention believed superior = non-randomised studies, waitlist controls more attractive
- Policy makers, commissioners, service leads can be unwilling to admit uncertainty
- Broader political reasons for preferring one treatment type over another
Ethical and political issues in randomisation
- Ethical
- Equipoise = ethical basis for medical research that involves assigning patients to different treatments
- Clinical equipoise = genuine uncertainty in the expert medical community over whether one treatment will be more beneficial
- It is not ethically … to randomise patients to a treatment known to be inferior
- Political
- Even when there is genuine uncertainty, new intervention … superior = non-randomised studies, waitlist controls more …
- Policy makers, commissioners, service leads can be unwilling to admit uncertainty
- Broader political reasons for preferring one treatment type over another
- Ethical
- Equipoise = ethical basis for medical research that involves assigning patients to different treatments
- Clinical equipoise = genuine uncertainty in the expert medical community over whether one treatment will be more beneficial
- It is not ethically acceptable to randomise patients to a treatment known to be inferior
- Political
- Even when there is genuine uncertainty, new intervention believed superior = non-randomised studies, waitlist controls more attractive
- Policy makers, commissioners, service leads can be unwilling to admit uncertainty
- Broader political reasons for preferring one treatment type over another
Ethical and political issues in randomisation
- Ethical
- Equipoise = ethical basis for medical research that involves assigning patients to different treatments
- Clinical equipoise = genuine uncertainty in the expert medical community over whether one treatment will be more beneficial
- It is not ethically acceptable to randomise patients to a treatment known to be inferior
- Political
- Even when there is genuine uncertainty, new intervention believed superior = non-randomised studies, waitlist controls more attractive
- Policy makers, commissioners, service leads can be unwilling to admit …
- Broader political reasons for … one treatment type over another
- Ethical
- Equipoise = ethical basis for medical research that involves assigning patients to different treatments
- Clinical equipoise = genuine uncertainty in the expert medical community over whether one treatment will be more beneficial
- It is not ethically acceptable to randomise patients to a treatment known to be inferior
- Political
- Even when there is genuine uncertainty, new intervention believed superior = non-randomised studies, waitlist controls more attractive
- Policy makers, commissioners, service leads can be unwilling to admit uncertainty
- Broader political reasons for preferring one treatment type over another
Equipoise = ethical basis for medical … that involves assigning … to different …
Equipoise = ethical basis for medical research that involves assigning patients to different treatments
Clinical … = genuine uncertainty in the expert medical community over whether one treatment will be more beneficial
Clinical equipoise = genuine uncertainty in the expert medical community over whether one treatment will be more beneficial
Practical issues in randomisation
- Practical:-
- … and …
- … randomisation needed for some scenarios; cluster-based
- There may be no research evidence suggesting a difference in efficacy between two arms of a trial but that does not stop participants from having a preference.
- Strong preferences between trial treatments may make it harder to recruit patients
- They don’t want to be randomised
- “Watch and wait” or “treatment as usual” may be seen as inferior
- Practical:-
- Money and resources
- Complex randomisation needed for some scenarios; cluster-based
- There may be no research evidence suggesting a difference in efficacy between two arms of a trial but that does not stop participants from having a preference.
- Strong preferences between trial treatments may make it harder to recruit patients
- They don’t want to be randomised
- “Watch and wait” or “treatment as usual” may be seen as inferior
Practical issues in randomisation
- Practical:-
- Money and resources
- Complex randomisation needed for some scenarios; cluster-based
- There may be no research evidence suggesting a difference in efficacy between two arms of a trial but that does not stop participants from … … …
- … preferences between trial treatments may make it … to recruit patients
- They don’t want to be …
- “Watch and wait” or “treatment as usual” may be seen as …
- Practical:-
- Money and resources
- Complex randomisation needed for some scenarios; cluster-based
- There may be no research evidence suggesting a difference in efficacy between two arms of a trial but that does not stop participants from having a preference.
-
Strong preferences between trial treatments may make it harder to recruit patients
- They don’t want to be randomised
- “Watch and wait” or “treatment as usual” may be seen as inferior
BIAS
- Generally - ‘a partiality that prevents … … of an issue or situation’
- In … - ‘a tendency of an estimate to deviate in one direction from a true value’
- Bias is any departure of results from the truth
- Bias in RCTs occurs when systematic error is introduced into sampling or testing by selecting or encouraging one outcome or answer over others
- Bias is independent of both sample size and statistical significance (sometimes greater samples increase present bias)
- Generally - ‘a partiality that prevents objective consideration of an issue or situation’
- In statistics - ‘a tendency of an estimate to deviate in one direction from a true value’
- Bias is any departure of results from the truth
- Bias in RCTs occurs when systematic error is introduced into sampling or testing by selecting or encouraging one outcome or answer over others
- Bias is independent of both sample size and statistical significance (sometimes greater samples increase present bias)
BIAS
- Generally - ‘a partiality that prevents objective consideration of an issue or situation’
- In statistics - ‘a tendency of an estimate to deviate in one direction from a true value’
- Bias is any departure of … from the truth
- Bias in RCTs occurs when … error is introduced into sampling or testing by selecting or encouraging one … or answer over others
- Bias is independent of both sample size and statistical significance (sometimes greater samples increase present bias)
- Generally - ‘a partiality that prevents objective consideration of an issue or situation’
- In statistics - ‘a tendency of an estimate to deviate in one direction from a true value’
- Bias is any departure of results from the truth
- Bias in RCTs occurs when systematic error is introduced into sampling or testing by selecting or encouraging one outcome or answer over others
- Bias is independent of both sample size and statistical significance (sometimes greater samples increase present bias)
BIAS
- Generally - ‘a partiality that prevents objective consideration of an issue or situation’
- In statistics - ‘a tendency of an estimate to … in one direction from a true value’
- Bias is any departure of results from the …
- Bias in … occurs when systematic error is introduced into sampling or testing by selecting or encouraging one outcome or answer over others
- Bias is independent of both sample size and statistical significance (sometimes greater samples increase present bias)
- Generally - ‘a partiality that prevents objective consideration of an issue or situation’
- In statistics - ‘a tendency of an estimate to deviate in one direction from a true value’
- Bias is any departure of results from the truth
- Bias in RCTs occurs when systematic error is introduced into sampling or testing by selecting or encouraging one outcome or answer over others
- Bias is independent of both sample size and statistical significance (sometimes greater samples increase present bias)
BIAS
- Generally - ‘a partiality that prevents objective consideration of an issue or situation’
- In statistics - ‘a tendency of an estimate to deviate in one direction from a true value’
- Bias is any departure of results from the truth
- Bias in RCTs occurs when systematic error is introduced into sampling or testing by selecting or encouraging one outcome or answer over others
- Bias is independent of both … … and … … (sometimes greater samples increase present bias)
- Generally - ‘a partiality that prevents objective consideration of an issue or situation’
- In statistics - ‘a tendency of an estimate to deviate in one direction from a true value’
- Bias is any departure of results from the truth
- Bias in RCTs occurs when systematic error is introduced into sampling or testing by selecting or encouraging one outcome or answer over others
- Bias is independent of both sample size and statistical significance (sometimes greater samples increase present bias)