Vaccines: Fact and FictionPamela Wood, MD

PediatricianUTHSCSA

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 cases110 in California + 7 other states

49 (45%) unvaccinated12: too young28: 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 ∼3000 AC-Pertussis 2–5

WC-Pertussis ∼3000 Polio 15 Polio 15

Polio 15 Measles 10 Measles 10

Total ∼3217 Mumps 9 Mumps 9

Rubella 5 Rubella 5

Total ∼3041 Hib 2

Varicella 69

Pneumococcus 8

Hepatitis B 1

Total 123–126

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 cellshttp://www.niaid.nih.gov/topics/vaccines/understanding/Pages/howWork.aspx

Types of Vaccines

• Live virus: contain weakened (attenuated) form of the viruse.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 feverB. History of redness at pain at vaccine site with previous doseC. 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 ControlAddress 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. All of the current childhood vaccinesB. Measles vaccineC. Influenza vaccineD. 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 RingChief 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.htmlAmerican Academy of Pediatrics:http://www2.aap.org/immunization/families/faq/VaccineStudies.pdfSeth Mnookin. The Panic Virus: the true story behind the vaccine-autism controversy.