Week 4 (Part 2): Vaccine Controversies

Question 1

What did Andrew Wakefields paper suggest?

- Why did it cause a drop in vaccination rates?

Answer 1

In 1998, Andrew Wakefield and 12 of his colleagues published a case series in theLancet, which suggested that the measles, mumps, and rubella (MMR) vaccine may predispose to behavioral regression and pervasive developmental disorder in children.
- Despite the small sample size (n=12), the uncontrolled design, and the speculative nature of the conclusions, the paper received wide publicity, and MMR vaccination rates began to drop because parents were concerned about the risk of autism after vaccination

Question 2

Why was Andrew Wakefield’s paper retracted?

Answer 2

There was a short retraction of the interpretation of the original data by 10 of the 12 co-authors of the paper.

• According to the retraction, “no causal link was established between MMR vaccine and autism as the data were insufficient”.
• This was accompanied by an admission by theLancet that Wakefieldet al. had failed to disclose financial interests (e.g., Wakefield had been funded by lawyers who had been engaged by parents in lawsuits against vaccine-producing companies).
• However, theLancetexonerated Wakefield and his colleagues from charges of ethical violations and scientific misconduct.

Question 3

Why did the Lancet retract Andrew Wakefields paper?

Answer 3

TheLancetcompletely retracted the Wakefieldet al.paper in February 2010, admitting that several elements in the paper were incorrect, contrary to the findings of the earlier investigation.

• Wakefieldet al.were held guilty of ethical violations (they had conducted invasive investigations on the children without obtaining the necessary ethical clearances) and scientific misrepresentation (they reported that their sampling was consecutive when, in fact, it was selective).
• This retraction was published as a small, anonymous paragraph in the journal, on behalf of the editors.

Question 4

What was Andrew Wakefield found guilty of?

Answer 4

Finally Wakefieldet al. were guilty of deliberate fraud (they picked and chose data that suited their case; they falsified facts).

• TheBritish Medical Journalhas published a series of articles on the exposure of the fraud, which appears to have taken place for financial gain.
• The Wakefield fraud is likely to go down as one of the most serious frauds in medical history

Question 5

What did epidemiology studies reveal after Andrew Wakefields article was posted?

Answer 5

Almost immediately afterward, epidemiological studies were conducted and published, refuting the posited link between MMR vaccination and autism.
- The logic that the MMR vaccine may trigger autism was also questioned because a temporal link between the two is almost predestined:
both events, by design (MMR vaccine);
or definition (autism), occur in early childhood.
- Taken together, some dozen studies have now shown that the age of onset of ASD, the severity or course of ASD, and the risk of ASD recurrence in families does not differ between vaccinated and unvaccinated children.
- In the largest-ever study of its kind (95,727 children), researchers again found that the measles-mumps-rubella (MMR) vaccine did not increase risk for autism spectrum disorder (ASD) - This proved true even among children already considered at high risk for the disorder.

Question 6

What did the release of Andrew Wakefields article spark?

• Why?
• Who did it affect?

Answer 6

Sparked new measles cases and outbreaks because parents were fearful of autism

• Immunization rates were decreasing, and number of infections were increasing
• The majority of the people getting measles were the unvaccinated ones

Question 7

What is vaccine efficacy vs. vaccine effectiveness?

Answer 7

Vaccine efficacy refers to the vaccine’s ability to prevent illness in people vaccinated in controlled studies.

Vaccine effectiveness refers to the vaccine’s ability to prevent illness in people in the “real world”.

Question 8

How do vaccines prevent against disease (2)?

Answer 8

1) First, vaccine administration results in immunity to the recipient.
- However, this is not a perfect system because not all healthy individuals respond optimally to all vaccines, leaving some susceptible to disease despite immunization.

2) Another caveat is that due to age or medical reasons, not all individuals can be immunized.
- Examples include infants who will not be fully protected until they have completed a series of immunizations and children with cancer who are undergoing chemotherapy who cannot be vaccinated or, if vaccinated, will not respond well.
- These special groups must therefore rely on a second, indirect form of protection termed community immunity (or herd immunity).

Question 9

What is herd immunity?

Answer 9

Herd immunity refers to the phenomenon whereby if enough individuals in a community are immunized, diseases cannot spread as well in the immunity of a population against a specific infectious disease.
- The resistance of that population to the spread of an infectious disease is based on the percentage of people who are immune and the probability that those who are still susceptible will come into contact with an infected person.

Question 10

The proportion of the population required to be immune to reach herd immunity depends on… a number of factors, the most important one being the transmissibility of the infectious agent either from a symptomatically infected person or from an asymptomatically colonized person.

Answer 10

… a number of factors, the most important one being the transmissibility of the infectious agent either from a symptomatically infected person or from an asymptomatically colonized person.

Question 11

What is the reproductive number (Ro)?

- High vs. low infectious diseases?

Answer 11

The reproduction number (R0), also called the basic reproductive rate, is defined as the average number of transmissions expected from a single primary case introduced into a totally susceptible population.
- Diseases that are highly infectious have a high R0(for example, measles) and require higher immunization (vaccine) coverage to attain herd immunity than a disease with a lower R0(for example, rubella,Haemophilus influenzaetype b).
Immunization coverage refers to the proportion of the population (either overall or for particular risk groups) that has been immunized against a disease.

Question 12

How is transmission stopped?

- Example

Answer 12

To stop transmission of a given disease, there needs to be at least a specified percentage (1 minus (1/R0)) of the population immune to the disease.
- For example, measles has an estimated R0of 15; therefore, at least 94% (1 minus (1/15) = 94%) of the population needs to be immune to prevent transmission of measles

Question 13

What % of children in Canada have never had a vaccine?

Answer 13

1.5-3%

Question 14

How many parents believe vaccines are directly linked to Austism?

Answer 14

20%

Question 15

What % of parents believe that a vaccine can cause the same disease it is meant to prevent?

Answer 15

37%

Question 16

What % of parents are concerned about potential side effects from vaccines.

Answer 16

70%

Question 17

What is a minority belief of vaccine elimination?

Answer 17

The belief that homeopathy and chiropractic manipulations can eliminate the need for vaccines

Question 18

Is it true that vaccines contain antigens that children can actually get the disease from in a vaccine?
- Dead vs. Live Virus

Answer 18

The answer is almost never.

• With inactivated (killed) vaccines, it isn’t possible.
• A vaccine causing full-blown disease would be extremely unlikely.

A dead virus or bacteria, or part of a virus or bacteria, can’t cause disease.

With live vaccines, some children get what appears to be a mild case of the disease (for exam- ple what looks like a measles or chickenpox rash, but with only a few spots).

Question 19

Why should parents not be concerned with the number of shots their children receive?

Answer 19

The reason why most vaccines require multiple doses is that inactivated vaccines contain a fixed amount of disease antigen (virus or bacteria) that builds immunity in phases by boosting with each dose to a protective level whereas in the case of live vaccines, the antigen in the vaccine reproduces itself and spreads throughout the body.

• A single dose, therefore, produces satisfactory immunity in most children.
• However, because not all children respond to the first dose, a second is given to assure immunity.

Question 20

Why should parents not be concerned to adverse reactions of vaccines?

Answer 20

While vaccines are safe, and although some children can experience adverse reactions, they are mostly local and self- limited.

• Minor reactions include redness, pain at site of injection, which occurs, depending on the study, in 5 to 25 percent; fever in 10 to 25 percent; prolonged crying in 0.001 percent (diphtheria, tetanus and acellular pertussis vaccine) to 2 percent (Haemophilus influenza type b); vom- iting in 2 to 5 percent and headache in 5 to 50 percent.
• Moderate reactions like febrile seizures have been estimat- ed to occur in one in 1,000 to one in 14,000 children.
• Severe adverse effects including anaphylactic reactions (life threatening allergic reactions) are rare (less than one in 1 million).
• The risk of encephalitis/encephalopathy with measles vaccine is one in 3 million; however, the risk of encephalitis from measles infection is one in 1,000.

Question 21

Why should parents not be concerned with what is in vaccines?

Answer 21

Arguably the most important of the controversies regarding both the fears of direct adverse effect and allergic response to immunization surrounds the question, “So, what is in vaccines?”
- Some vaccines also contain adjuvants, which are substances that help vaccines produce a stronger immune response.

In addition, some vaccines come in multiple dose vials which often contain a preservative – thimerosol, formaldehyde, aluminum
- In many of these examples, vaccine ingredients could be toxic . . . at much higher doses.
- But at a very low dose, even a highly toxic substance can be safe.
We might not be aware of it, but we are exposed to small amounts of these same “toxic” substances every day.