The Immune System

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Vaccination

Why aren’t they always effective?

Natural infections persist within the body for a long time so the immune system has time to develop an effective response, vaccinations from dead m-os do not do this.

Less effective vaccines need booster injections to stimulate secondary responses

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Vaccination

Why aren’t they always effective?

Some people don’t respond well/at all to vaccinations

Defective immune systems

Malnutrition particularly protein

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Vaccination

Why aren’t they always effective?

Antigenic variation caused by mutation

Antigenic drift – small changes (still recognised by memory cells)

Antigenic shift – large changes (no longer recognised)

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Vaccination

Why aren’t they always effective?

No vaccines against protoctists (malaria and sleeping sickness)

Many stages to Plamodium life cycle with many antigens so vaccinations would have to be effective against all stages (or be effective just against infective stage but given in very small time period).

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Vaccination

Why aren’t they always effective?

Sleeping sickness – Trypanosoma has a thousand different ags and changes them every 4-5 days

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Vaccination

Why aren’t they always effective?

Antigenic concealment parasites live inside body cells

Plasmodium – liver and blood cells

Parasitic worms – cover themselves in host proteins

HIV – live inside T-helper cells

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Smallpox

Symptoms

Red spots containing transparent fluid all over body.

Spots fill with pus

Eyelids swell and become glued together

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Smallpox

Mortality

12-30% died

Survivors often left blind and disfigured with scabs.

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Smallpox

Eradication programme

Started by WHO in 1956

Aimed to rid world of smallpox by 1977

Involved vaccination and surveillance

Over 80% of populations at risk of the disease were vaccinated

After any reported case everyone in the household and 30 surrounding households vaccinated – RING VACCINATION

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Smallpox

Eradication programme

Last case of smallpox reported in Somalia in 1977