Vaccines: Fact and Fiction
Pamela Wood, MD
Pediatrician
UTHSCSA
March 21, 2015
True or False?
Current vaccines protect against diseases
that are no longer a problem in the US.
• Polio (poliomyelitis) affects mainly
children under 5 years
• One in 200 infections leads to
irreversible paralysis.
• Polio cases have decreased by over
99% since 1988
• In 2014, only 3 countries
(Afghanistan, Nigeria and Pakistan)
remain polio-endemic
• Highly contagious
• One of leading causes of death
in young children globally
(145,700 deaths in 2013)
• Complications: blindness;
encephalitis; dehydration;
pneumonia
Disneyland measles outbreak
125 cases
110 in California + 7 other states
49 (45%) unvaccinated
12: too young
28: intentionally unvaccinated
47 (43%): unknown status
Vaccine components over time
1900
1960
1980
2000
Vaccine
Proteins
Vaccine
Proteins
Vaccine
Proteins
Vaccine
Proteins/Polysaccharides
Smallpox
∼200
Smallpox
∼200
Diphtheria
1
Diphtheria
1
Total
∼200
Diphtheria
1
Tetanus
1
Tetanus
1
Tetanus
1
WC-Pertussis
AC-Pertussis
2–5
WC-Pertussis
∼3000
Polio
∼3000
15
Polio
15
Polio
Total
15
Measles
Mumps
10
9
Measles
Mumps
10
9
Rubella
Total
5
Rubella
Hib
5
2
Varicella
Pneumococcus
Hepatitis B
Total
69
8
1
123–126
∼3217
∼3041
Which of the following statements is CORRECT?
A. Infants under 6 months of age cannot respond to killed
vaccines.
B. Giving multiple vaccines at the same time results in a
decreased immune response to the individual components.
C. The 2014 vaccination schedule protects against more
pathogens than the 1980 vaccination schedule.
Rationale for current vaccination schedule:
• Provide immunity early in life, before exposure
• Protect against diseases that are threats
• Vaccines tested for safety and effectiveness
• Do not overload the immune system
• No known benefits of delayed schedules
• Reviewed annually by CDC/ACIP
Changes in immunoglobulin levels with age
Antigen: foreign substance that, when introduced into the
body, is capable of stimulating an immune response; found
on surface of virus and bacteria
Antibody (immunoglobulin): a protein produced by plasma
cell when it detects harmful substances, called antigens
Macrophage:
-
Ingest virus; travel to lymph node
-
Present viral parts to T cells and B cells in the lymph
node
B cell (humeral immune response; antibody response):
- differentiate into plasma cells (make antibodies) or
memory B cells
T cells (cellular immune response): helper T; killer T
Both T and B cells can become memory cells
http://www.niaid.nih.gov/topics/vaccines/understanding/Pages/howWork.aspx
Types of Vaccines
• Live virus: contain weakened (attenuated) form of the virus
e.g. measles, mumps, and rubella (MMR) vaccine; varicella (chickenpox) vaccine
• Killed (inactivated): contain protein(s) or other small pieces taken
from a virus or bacteria. e.g. inactivated polio vaccine
• Toxoid: contain toxin or chemical made by the bacteria or virus. e.g.
diphtheria; tetanus vaccines.
• Conjugate: link viral/bacterial antigen with a carrier protein to
enhance immune response. e.g. Hib (Haemophilus influenzae type B)
Why multiple doses necessary?
• Single does may not provide sufficient immunity (e.g. HIB)
• Immunity wanes over time; “booster” dose is needed (DTaP)
• Single dose does not produce immunity for everyone (e.g. measles)
• Vaccine components change over time (e.g. influenza)
Who should NOT receive a vaccine?
• Severe allergy to any vaccine component
• Severe reaction to same vaccine in past
• Individuals with certain immunodeficiencies (live vaccines)
Which of the following individuals should not
receive the MMR vaccine?
A. Current cough, “cold” and low-grade fever
B. History of redness at pain at vaccine site with previous dose
C. Receiving chemotherapy for leukemia
Risks of unimmunized child
• Child gets disease and exposes other individuals:
• Who are unimmunized
• Who are immunized but not immune
• Child incurs medical costs (self and others)
Herd Immunity
Herd immunity: form of indirect
immunity that occurs when large
percentages of a population have
become immune to an infectious
disease, thereby providing a
measure of protection for
individuals who are not immune
(source: Wikipedia)
Cocooning
• Vaccination strategy recommended by CDC
• Protect young infants from infection, e.g.
pertussis (whooping cough); influenza
Vaccine Safety
• Preapproval testing: safety & effectiveness
• Post-licensure testing:
– Vaccine Adverse Event Reporting System (VAERS)
– Vaccine Safety Datalink (network of 9 managed care organizations)
– FDA inspection of vaccine batches
Vaccine Information Sheet (VIS)
Developed/ updated by Centers for Disease Control
Address the following issues:
• Why get vaccinated?
• Who should get vaccinated; Who should not get vaccinated
• What are the risks?
• What if there is a serious reaction?
• National Vaccine Injury Compensation Program
True or False?
Several childhood vaccines contain mercury, which is toxic to the
nervous system.
Which of the following vaccines contain a
substance similar to mercury?
A.
B.
C.
D.
All of the current childhood vaccines
Measles vaccine
Influenza vaccine
Pneumococcal vaccine
Thimerosal
• Preservative used in multi-dose vials of influenza vaccine
• Degraded to ethylmercury
• Ethylmercury: broken down quickly by the body; less likely to accumulate in
the body
• Methylmercury: found in food chain; toxic at high levels
• No evidence that thimerosal associated with increased risk of autism
• Multiple studies: Sweden, Denmark, Canada, UK, US
• Institute of Medicine report (2004)
True or False?
Vaccination has been associated with an increased risk of autism.
Vaccines and autism: the facts
• Autism: unknown cause; rates increasing
• Autism symptoms often recognized at 1-2 years age
• Andrew Wakefield: 1998 Lancet paper linking autism & MMR
– Subsequent large population-based studies: no link
– Study retracted by Lancet; author guilty of professional misconduct
– Data misrepresented/altered (BMJ 2011)
Over the last two decades, extensive research
has asked whether there is any link between
childhood vaccinations and autism. The results
of this research are clear: Vaccines do not cause
autism. We urge that all children be fully
vaccinated.
Rob Ring
Chief Science Officer, Autism Speaks
Summary
• Current recommended vaccinations are safe and effective
• No vaccines are 100% effective or 100% risk-free
• Current recommendations based on best available scientific data
• Schedule reviewed/updated annually
References
Center for Disease Control and Prevention:
http://www.cdc.gov/vaccines/hcp/patient-ed/conversations
Children's Hospital of Philadelphia - Vaccine Education Center:
http://www.chop.edu/service/vaccine-education-center/home.html
American Academy of Pediatrics:
http://www2.aap.org/immunization/families/faq/VaccineStudies.pdf
Seth Mnookin. The Panic Virus: the true story behind the vaccineautism controversy.