LO: Explain the immunological response to an immunisation

• Immunisation - susceptible individual has protection to an infection
• Vaccination - giving a vaccine
• Immunogenicity - ability to provoke an immune response
• Infection - invasion/multiplication of microbe
• Disease - damage of host, resulting in symptoms

Immunisation

• Prevent disease - reduce symptoms and reduce transmission
• Prevent infection
• Outbreak control/eradication

LO: Distinguish between active and passive immunisation

Passive immunity

• Transfer of pre-formed antibodies (natural/synthetic)
• Rapid protection - vaccines take less than 1 week
• Give to all patients
• Short-lived
• No memory - immune system not involved
• Cost

LO: Discuss the different types of vaccine available and give examples

Active immunity

Live-attenuated

• Serial passage in tissue culture, can infect but usually does not cause disease
• Immunogenic - resembles natural infection
• Replicates at site of infection - mucosal immunity
• Potential for vaccine strain infection/disease
• Not suitable in pregnancy
• Needs mature adaptive immune system
• BCG, influenza, MMR, polio

Inactivated whole cell

• Pathogen killed or altered by chemical or physical processes
• Cannot replicate/cause disease
• Given to more patients
• Less immunogenic than live vaccine, more boosters needed
• Inactivated polio, hepatitis A, rabies

Inactivated toxin

• Toxoid - chemically treated to eliminate toxicity whilst maintaining immunogenecity
• Bacteria may not cause disease themselves so target the toxin
• Diphtheria, tetanus, pertussis

Subunit-recombinant proteins

• Specific viral protein produced in an expression system
• Hepatitis B

Polysaccharides

• Purified bacterial polysaccharide
• Poorly immunogenic
• Some meningococcal/pneumococcal vaccines

Conjugated polysaccharides

• Purified bacterial polysaccharide linked to a protein
• H. influenzae, pneumococcal, meningococcal

Adenovirus vectors

• Double stranded DNA - remove replication genes
• Insert gene coding protein
• Strong expression of viral proteins
• Human adenovirus not immunogenic
• SARC-CoV-2 (AstraZeneca)

Messenger RNA

• Injection of a nucleic acid (mRNA) that is translated in cells to produce the target antigen

• Can produce new vaccine quickly

• Messenger RNA less stable - refrigeration
  

• SARS-CoV-2 (Pfizer and Moderna)

Adjuvants

• Increase immunogenicity - stimulate immune system
• Aluminium phosphate/hydroxide commonly used
• Thought to cause increased inflammation

LO: Describe the immunisation programme in the UK

Pre-exposure

• Children - UK routine childhood immunisation programme
• Adults:
  • 65 years of age - pneumococcal polysaccharide vaccine, annual influenza vaccine
  • 70 years of age - varicella zoster (shingles vaccine)
• Pregnant women - influenza vaccine before flu season, pertussis vaccine from 16 weeks gestation
• Adults and children at high risk due to underlying health condition
• Those at risk due to occupation, lifestyle or contacts
• Travellers

UK immunisation schedule

Routine childhood schedule

• 8 weeks: 6-in-1 vaccine (1st), rotavirus (1st), MenB (1st)
• 12 weeks: 6-in-1 vaccine (2nd), rotavirus (2nd), MenB (2nd)
• 16 weeks: 6-in-1 vaccine (3rd), pneumococcal vaccine (PCV, 1st)
• 1 year: MMRV vaccine (1st), pneumococcal vaccine (2nd), MenB (3rd)
• 1.5 year: 6-in-1 vaccine (4th), MMRV vaccine (2nd)
• 3 years and 4 months: 4-in-1 pre-school booster (dTaP/IPV), MMRV vaccine (catch-up)
• 2-15 years: annual children's flu vaccine (every year until finishing Year 11)
• 12-13 years: HPV vaccine (Gardasil 9)
• 14 years: Td/IPV vaccine (3-in-1 teenage booster), MenACWY vaccine
  6-in-1 vaccine = DTaP/IPV/Hib/HepB

Post-exposure

• Immunoglobulins and vaccines can be given after an exposure to reduce risk of disease/attenuate disease
• Immunoglobulin - works immediately
• Vaccine = develops strong, long lasting immunity
• Immunoglobulins can inadvertently neutralise vaccine - may need extra doses

LO: List contraindications to, and side effects of, immunisations

Vaccines

• Weigh up risk of disease vs benefits of immunisation

Adverse effects

• Related to the immunogen or other components of the vaccine
• Most commonly local reactions - pain, swelling and redness
• General systemic effects - fever, headache and malaise
• Some vaccines may be associated with a rash - MMR, VZV
• Anaphylaxis is rare
• Rare adverse effects vary by vaccine

Contra-indications

• Few people unable to receive vaccines
• Anaphylaxis to previous vaccine or component
• Immunosuppression
• Pregnancy
• Immunisation may need to be deferred - acutely unwell, other vaccines given recently, immunoglobulin therapy

Immunisation failure

• No vaccine is 100% effective
• Primary vaccine failure:
  • Vaccine factors
  • Host factors
  • Inappropriate vaccine schedule
• Secondary vaccine failure:
  • Immunity develops initially, with time immunity wanes (immuno-senescence)