Lecture 13: Control/Prevention of Infectious Disease + Vaccine Distribution

What diverse priority grouping can vaccine distribution be dependent on

A. Occupation

B. Sickest or most medically vulnerable

C. Stages of life

D. Social vulnerability

E. Procedure applied to whole population (lottery)

How can occupation play a role in priority grouping

1. Healthcare workers (HCW) Professional status & proximity to pandemic-affected patients

2. Vaccine manufacturers

3. Emergency services workers

4. Basic infrastructure (Food distribution, transportation, etc.)

How can stages of life play a role in priority grouping

1. Children

• Minimize infection in community

• Longest life ahead

2. Adolescence to pre-middle age

• Future collective benefit

How can social vulnerability a role in priority grouping

‘Hard-to-reach’ groups

Socially stigmatized (Ex: Homeless, Prisoners, obese)

How can vaccine procedure be applied to whole population

Applied to whole population instead of setting priority groups in advance

Example: lottery system

Priority Group 1 for Covid-19 vaccine?

Frontline/essential workers

Priority Group 2 for Covid-19 vaccine?

1. Covid-19 Health Disparity Group

2. High risk for severe disease

3. High infection risk

ex:

• Age 65+ in nursing home

• Racial/ethnic groups with higher risk of infection, severe disease, death

• Underlying chronic conditions linked to high risk & live in crowded environments

Priority Group 3 for Covid-19 vaccine?

1. Covid-19 Health Disparity Group

2. High risk for severe disease

3. No high risk for infection

Underlying chronic conditions linked to higher risk of severe disease/death who can safely socially distance

ex:

• High BMI who attend school remotely

• 65 or older who can work remotely and shelter at home

Priority Group 4 for Covid-19 vaccine?

1. Covid-19 Health Disparity Group

2. No high risk for severe disease

3. High risk for infection

ex:

• Young, healthy adults working in crowded environments

• Young, healthy adults aged 18 – 22 living in college dorms

• Healthy adults under age 65 or older living in prisons '

• Healthy adults under age 65 or older working in high-exposure environments

Who gets no priority for covid-19 vaccine

1. Not in Covid-19 health disparity group

2. Not an essential/frontline worker

OR

1. In Covid-19 health disparity group

2. No high risk severe disease/death

3. No high risk infection

What matters the most when it comes to vaccine distribution

1. Prevent the most illness

2. Save the most lives

3. Benefiting greatest # of people

4. Maximizing quality of life years saved (QALYS) & minimizing years of life lost (YLL)

5. Promoting justice, solidarity and trust in government and public health systems

Who is it most important to save when it comes to vaccine distribution

Saving the worst off

Saving those most likely to recover

Saving those most likely to contribute to a flourishing society

Saving those who can most usefully contribute to minimizing impact of pandemic

Targeting those most likely to play significant role in spreading infections (i.e., children)

What do those most likely to get a vaccine have?

• rapid digital connection

• time to repeatedly refresh link or hold on phone for hours

• ability to travel to vaccination site (often by car)

• trust in safety and efficacy of vaccine

What are some reasons people w/ high risk for severe illness/death do not seek vaccine

• lack of awareness

• barriers to vaccine access

• concerns about vaccine

Strategies to mitigate disparities

1. Prioritize to zip codes most severely affected (typically have high index of economic hardship)

2. Partner with local health care institutions, community organizations, and other trusted sources to promote vaccine awareness & uptake

3. Prioritize distribution to those who face mobility/transportation barriers

4. Simplify registration process

How to prioritize distribution to those who face mobility/transportation/time barriers

1. Deliver vaccine to homebound older person

2. Vaccination sites near public transportation

3. Hours of operation accessible to those who work during standard business hours

How to simplify vaccine registration process

1. Have options that don’t require internet or digital platforms

2. Accessible to those with limited English proficiency or limited literacy

3. Should not require nonessential documentation

4. Options that do not require pre-registration

Various ways a pathogen can be eliminated from an environment

Sterilization

Everything (even non-pathogens) is completely destroyed/removed

Sterilant

Agent that helps w/ sterilization

Ex: chemical agents, like ethylene oxide (C2H4O) can be used to sterilize medical devices

Disinfection

Killing/inhibiting/removing microorganisms that may cause disease on INANIMATE objects

Usually done via chemical agents

Sanitization

Cleaning/disinfecting inanimate objects deemed safe by public health standards

Example: restaurant utensils

Antisepsis

Controlling microbes on living tissue through chemical agents

Antiseptics kill/inhibit pathogen growth

Less toxic than disinfectants

-cide vs -static

-cide = to kill

• biocide: an agent that can kill living (can control microorganisms)

• Germicide

• Bactericide

• Fungicide

• Viricide

-static: inhibit growth but does not kill

• if removed/diluted → effect is gone

• bacteriostatic

• fungistatic

Exponential microbial death

Population decreases by the same fraction at constant intervals

• ex: at a particular temp

  • 10% of organisms die in 1st min

  • 10% of living organisms die in 2nd min

  • 10% of living after 2nd wmin will die in 3rd mijn

Decimal reduction time (D value)

Time to kill 90% of microorganisms in a sample at a specific time

Types of physical agents for controlling microbes

1. Filtration

   1. Air

   2. Liquid

2. Heat

   1. Moist

   2. Dry

3. Radiation

   1. UV

   2. ionizing

Air filtration

Type of physical agent to control microorganisms

Examples

• HEPA filters

  • high-efficiency particle air

  • fiberglass

  • removes 99.97 % of particles ≥ 0.3 µm

  • also captures nanoparticles (≤0.1 µm, like viruses)

• N95

  • excludes 95% of particles ≥ 0.3 µm

  • Hospitals/labs

Liquid filtration

Type of physical agent to control microorganisms

• Depth filter

  • Fibrous or granular material

  • Thick layers with lots of twisting channels of small diameter

  • Solution is sucked through & microbial cells ar trapped

• Membrane filters

  • Synthetic materials

  • Varity pore sizes

    • ~0.2µm in diameter

    • Removes most vegetative cells

Moist heat as a physical agent for removing microbes

• Autoclaves

  • Water boiled → Steam

  • Enters chamber & put under pressurew

  • 121 degrees C & 15 lbs of pressure

• Pasteurization

  • Controlled heating at temps well below boiling

  • Does not sterilize

  • Kills most pathogens, reducing spoilage

Dry heat as a physical agent for removing microbes

Less effective than moist

Does not corrode metal instruments

Sterilizes powders & oils

• Bench top incinerators to sterilize innoculating loops

UV Radiation to control microbial growth

Non-iodizing

260-280 nm

Causes pyrimidine dimer, which is lethal

• Pyrimidine = C & T

Limiting factor: Can’t penetrate well

Used in rooms in cabinets to sterilize air or exposed surfaces

Ionizing raditaion to control microbial growth — How many types?

3 types

• Gamma rays

• Electron beams

• X rays

Penetrates deep

Damages DNA & produces peroxide

Destroys bacterial endospores & vegetative cells

Uses for ionizing radiation

Medical: antibiotics, hormones, syringes

Foods

Goal of chemical agents? What are some examples of chemical agents?

Be efffective against a wide range of microbes w/o being toxic to humans or corrosive to common material

Examples

1. Phenol

2. Soaps & detergent

3. Alcohol

4. Oxidizing agents

Joseph Lister

Sprayed phenol (a type of carbolic acid) into wounds, incisions, etc) & noticed it prevented infections

• Led to antisepsis in healthcare setting

Phenol & phenolic derivatives

Denature proteins and disrupts plasma membrane

Advantages:

• effective in presence of organic material

• remains active on surface for a long time after application

Disadvantages:

• Bad odor & causes skin irritation

Example of phenol-derivative

Triclosan

• Phenol-derived antiseptic

• Binds to enoyl-ACP reductase (bacterial enzyme)

• Inhibits fatty acid synthesis (important for cell membrane synthesis)

Soaps & detergents

Surfactants (amphipathic)

• allows them to break down and lift away dirt, oil, and bacteria from surfaces or skin

Removes microbes, oil

Action of removing microbes increases w/ scrubbing

Alcohols—what does it cause? What can it inactivate/kill?

• Disinfectants (inanimate) & antiseptics (living tissue)

• Bactericidal

• Inactivates viruses

• Dissolves/disrupts PM

• Ex: ethanol/isopropanol (hand sanitizer)

Oxidizing agents

Strip electrons from molecules

Examples

• H2O2 (3% solution) can be used on skin wounds)

• Tincture of iodine

• Sodium hypochlorite (found in household bleach, swimming pools)

• Wastewater treatment (Chlorine/ozone)

What factors affect the effectiveness of antimicrobial agents

1. Population size

2. Cell type

3. High concentrations of antimicrobial agent

4. Longer duration of exposure

How does population size affect the effectiveness of antimicrobial agents

Fewer organisms = less time needed to achieve sterility

Table shows example of 40% death rate/min

How does cell type affect the effectiveness of antimicrobial agents

Vegetative cells are actively growing and more susceptible to agents

Younger cells are more susceptible than mature

Cells w/ endospores are more resistant

How does concentration of agent & duration of exposure affect the effectiveness of antimicrobial agents

Increased concentration destroys organisms faster (up to a point)

Longer duration of exposure leads to more killed

Phenolic component

Disinfectant screening test to see the effectiveness of a disinfectant

• Potency of a disinfectant is compared to phenol

• Series of identical dilutions to phenol & experimental disinfectant conducted

Methods of phenolic component test

20ºC water bath for 5 mins so all tubes come to same temp

Inoculated w/ 0.5 ml of test bacteria (Salmonella typhi & staphyloccus aureus

Test after 5, 10, 15 mins of innoculation

• Transfer into broth & incubate for 48 hours

• Find smallest concentration (highest dilution) that kills all organism after 10 mins

  • This dilution is used to calculate phenol coefficient

How to calculate phenol coefficient

Reciprocal of test disinfectant dilution divided by reciprocal for phenol

ex:

• test infectant dilution = 1/250

• phenol dilution = 1/250

• 250/250=1

  • test disinfectant has same effectiveness as phenol

• test disinfectant dilution = 1/450

• phenol dilution = 1/90

  • phenol coefficient: 450/90=5

T/F: higher phenol coefficient means a more effective disinfectant under those conditions

True