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IMMUNIZATION AND COLD CHAIN 2021 - DR CHIKAFUNA BANDA

Objectives

  • Define cold chain.
  • Cold chain system.
  • Cold chain equipment and its use.
  • Maintenance of cold chain equipment.
  • Control and monitoring of temperatures.
  • Cold chain during immunization sessions.
  • Breakdowns and emergencies.

Immunization

  • Definition: Immunization is the procedure by which the body is prepared to fight against a specific disease.
  • Types of Immunization:
    1. Passive Immunization
    2. Active Immunization

Passive Immunization

  • Definition: Passive immunization is produced without challenging the immune system of the body. It is achieved by the administration of serum or gamma globulins from a person who is already immunized (affected by the disease) to a non-immune person.
  • Methods of Acquisition:
    • Naturally: Acquired through maternal antibodies, for instance.
    • Artificially: Developed by injecting previously prepared antibodies using serum from humans or animals.
  • Utility: Useful for providing immediate protection against acute infections like tetanus, measles, etc.

Active Immunization

  • Definition: Active immunization is acquired by activating the immune system of the body. The body develops resistance against disease by producing antibodies following exposure to antigens.
  • Types of Acquisition:
    1. Naturally Acquired Active Immunization: Involves activation of immune system in response to a microorganism through clinical or subclinical infections.
    2. Artificially Acquired Active Immunization: Achieved by the administration of vaccines or toxoids.

Herd Immunity

  • Definition: A type of immunity that occurs when the vaccination of a portion of the population provides protection to unprotected individuals. The higher the number of immune individuals, the lower the likelihood that susceptible individuals will encounter an infectious agent.
  • Implications: It creates resistance to the spread of infectious disease in a group due to the presence of few susceptible members, making transmission unlikely.
  • Scenarios:
    • If only SOME get vaccinated: The virus spreads.
    • If MOST get vaccinated: Spreading is contained.

Vaccine

  • Definition: A vaccine is a substance that is introduced into the body to prevent disease produced by certain pathogens. It consists of dead pathogens or live but attenuated (artificially weakened) organisms. The vaccine induces immunity against the pathogen either by production of antibodies or by activation of T lymphocytes.
Types of Vaccine
  1. Live-attenuated (weakened) vaccines:
    • Contain modified strains of a pathogen (bacteria or viruses) that have been weakened but are able to multiply within the body and remain antigenic enough to induce a strong immune response.
  2. Killed-inactivated vaccines:
    • Produced by killing or inactivating bacteria or viruses through chemical treatment or heat.
  3. Sub-unit vaccines:
    • Include only the antigens that best stimulate the immune system.
    • Epitopes: Very specific parts of the antigen that antibodies or T cells recognize and bind to.
    • Lower chances of adverse reactions as they contain only essential antigens.
    • Types of Subunit Vaccines:
      • Toxoids
      • Protein vaccine
      • Recombinant protein vaccine
      • Polysaccharide-based vaccine
      • Conjugated vaccine
  4. Combination vaccines (mixed/multivalent):
    • Include more than one kind of immunizing agent.
    • Advantages:
      • Simplify administration
      • Reduce cost
      • Improve timelines of vaccination
      • Reduce storage needs.
      • Examples: DPT, DT, DP, MMR, etc.
      • POLYVALENT: Prepared from 2 or more strains of the same species.

Why Immunization?

  • Key strategy to child survival, protecting infants from diseases.
  • Lowers morbidity and mortality rates in children.
  • Indicator of a strong primary health care system.
Expanded Programme on Immunization (EPI)
  • Objectives:
    • Add more disease-controlling antigens to vaccination schedules.
    • Extend coverage to all corners of a country.
    • Spread services to reach less privileged sectors of society.
    • Strengthen routine immunization to meet vaccination coverage targets.
    • Accelerate control of vaccine-preventable diseases.
    • Spur research and development for the next generation of vaccines and technologies.

Barriers to Immunization

  1. Physical Barriers:
    • Waiting time
    • Distance
    • Discomfort
  2. Psychological Barriers:
    • Discourtesy
    • Endangered privacy

Reasons for Low Immunization Coverage

  • Failure to provide immunization.
  • Un-reached populations:
    • Unawareness
    • Socio-economic barriers
    • Geographic access.
  • Resistant populations.
  • Missed opportunities.
  • Improper logistics management.

The Cold Chain

  • Definition: The cold chain is the process used to maintain optimal conditions during the transport, storage, and handling of vaccines, starting from the manufacturer and ending with the administration of the vaccine to the client.
Cold Chain System - Elements
  1. Personnel: Individuals who use and maintain the equipment and provide health services.
  2. Equipment: Essential for safe storage and transportation of vaccines.
  3. Procedures: Manage the program while controlling the distribution and use of vaccines.
Cold Chain System Activities in Vaccine Facilities
  1. Receipt
  2. Storage
  3. Delivery

Vaccine Stability

  • All vaccines are sensitive biological substances.
  • Potency Loss: Occurs if exposed to temperatures outside the recommended range. Once potency is lost, it is irreversible.

Why is the Cold Chain Important?

  1. Vaccines are biological products that lose potency over time, and the process is irreversible, especially if proper storage conditions are not followed.
  2. Ensuring maximum benefit from immunizations is a responsibility to not waste scarce resources and to reduce wastage from errors.
  3. Assurance of a potent product enhances public health responsibility, contributing to public confidence in immunization programs.
  4. Compliance with SPC/Manufacturer requirements: Any vaccine that has not been stored from 2-8°C as per its licensing conditions is no longer a licensed product.
Cold Chain Equipment & Its Use
  • Equipment for Vaccine Transportation
  • Equipment for Vaccine Storage
Cold Chain Storage Equipment
  1. Walk-in Cold Rooms (WIC):
    • Store for larger quantities of vaccines, maintaining temperatures between 0 - 8 degrees Celsius.
    • Usage: Large quantities and secure facilities for reserves.
  2. Deep Freezers:
    • Maintain temperatures from -15°C to -25°C.
    • Used at district and Primary Health Care (PHC) levels. Can maintain temperature for 18-22 hours during power failure.
    • Capacity: 20-25 ice packs from a 140L deep freezer with 8 hours continuous supply.
  3. Ice Lined Refrigerators (ILR):
    • Used at both district and PHC levels, maintaining +2°C to +8°C.
    • Design: Better cold air retention with top-opening models.
    • Can keep vaccines safe with continuous supply for 8 hours within a 24-hour period.
Transport Equipment
  1. Cold Boxes:
    • Utilized for transporting vaccines, where fully frozen ice packs are placed at the bottom and sides. DPT, TT, DT should not contact the ice directly.
  2. Vaccine Carriers:
    • Carry small quantities (16-20 vials), used for out-of-reach sessions utilizing four ice packs.
  3. Day Carriers:
    • For very small quantities (6-8 vials), focuses on short-term transport for up to 2 hours using two ice packs.

Use of Diluents

  • Purpose: Specifically designed to reconstitute vaccines with respect to volume, pH, and other chemical properties. Must be stored at +2°C to +8°C in ILR. Only vaccines supplied and packaged by manufacturers should be used as diluents.

Vaccine Stability Considerations

  • Sensitivity to Heat and Cold:
    • Most sensitive vaccines include OPV and Measles (heat).
    • Cold sensitivity includes Hepatitis B and combination vaccines.
  • Temperature Monitoring: Must be recorded twice daily using dial thermometers.

Light Sensitivity

  • Vaccines sensitive to strong light include OPV, Measles, MMR, and others. It is essential to store vaccines in their original packaging until point of use to protect them from light exposure.

Storage Do's and Don'ts

DO's
  • Use a dedicated vaccine fridge.
  • Safeguard electricity supply, ensuring the fridge is no more than 50% full.
  • Place vaccines in clearly labeled plastic mesh baskets and group vaccines by type (Paediatric, Adult, Adolescent).
  • Regularly defrost/calibrate the fridge.
DON'Ts
  • Do not store food or medical specimens in the vaccine fridge.
  • Avoid placing the fridge in direct sunlight or near heat sources.
  • Do not store vaccines for more than 1 month at the PHC.
  • Avoid storing vaccines in the fridge doors or in solid plastic trays/containers within the fridge.
  • Keep vaccines away from fridge walls and cold air vents.

Transporting Equipment

  • Cold Boxes
  • Vaccine Carriers
  • Day Carriers
Ice Packs
  • Contains water (no salt should be added). Water should be filled up to the marked level. Leaking ice packs should be discarded.

Vaccine Potency Monitoring

  • Even if a vaccine loses some potency, its appearance may not change. Vaccine Vial Monitor (VVM) serves as an indicator attached to each vial recording exposure to heat.
    • If temperature exceeds +8°C, the indicator changes color, denoting vaccine damage.

Control and Monitoring of Temperature

  • Should be routine activity at the start and end of each working day.
  • Monitoring Devices:
    1. Thermometers
    2. Temperature record sheets
    3. Refrigerator or freezer thermostat
    4. Cold Chain Monitor Card (CCM)
    5. Vaccine Vial Monitor (VVM)
    6. Freeze watch indicator
    7. Vaccine shake test.
Thermometers
  • Fit every piece of cold chain equipment with a thermometer, typically a mercury thermometer.
Temperature Record Sheets
  • Record temperature of refrigerator or freezer twice daily – morning and afternoon. Report any malfunctions.
Cold Chain Monitor Card
  • Designed to track vaccines from manufacture to end usage. Kept with the vaccine batch, containing four windows that change color with temperature exposure.

Vaccine Vial Monitor (VVM)

  • Applied directly to vaccine vials to assess heat exposure over time. Displays cumulative heat effects while not directly measuring vaccine potency.
    • The inner square color change indicates exposure and degradation risk. The stages indicate safe usage or discarding of the vaccine.
Reading the VVM
  • Use vaccines based on the VVM status:
    • OK to Use: Inner square lighter than outer ring and within expiry date.
    • DO NOT USE: Matches or is darker than the outer ring, indicating it has reached or exceeded the discard point.

Freeze Watch Indicator

  • Indicates if the vaccine has been exposed to temperatures below 0°C. The indicator bursts and releases liquid when conditions drop below freezing.

Vaccine Stock Management

  • Accurate stocks must be maintained at each stage of the cold chain, ensuring there are neither too few nor too many vaccines on hand.
  • Estimation of Quantities Needed:
    • Determine the number of children to immunize annually and the number of doses required for each vaccine.
    • Consider vaccination deliveries planned, desired reserve stocks, and balance of stock remaining in the main store.

Vaccine Stock Records

  • Keep complete and updated stock records for all units:
    • Name of vaccine, batch number, expiry date, and vial size.
    • Quantity and source of supply received.
    • Quantity issued and recipient details.
    • For certain vaccines, record diluent quantities received and issued, maintaining balance after each transaction.

Managing The Cold Chain

  1. Uncontrollable Factors:
    • Weather delays
    • Handling issues
    • Cargo placement
  2. Controllable Factors:
    • Packaging
    • Routes
    • Carriers
    • Delivery time
Final Note
  • The cold chain is only as strong as its weakest link.