Bacterial & Viral Vaccines

Question 1

List the diseases for which vaccines are used in the UK immunisation schedule and explain the reasons for this schedule

Answer 1

UK Immunisations:

• DTaP/IPV/Hib/Hep: A combined vaccine protecting against diphtheria, tetanus, pertussis (whooping cough), polio, Haemophilus influenzae type b (Hib), and hepatitis B. Typically given at 8, 12, and 16 weeks of age
• Pneumococcal Conjugate Vaccine (PCV): Given at 8 weeks, 16 weeks, and one year of age, this vaccine protects against pneumococcal bacteria, which can cause pneumonia, meningitis, and sepsis
• Rotavirus Vaccine: This oral vaccine is given at 8 and 12 weeks of age. Rotavirus is a common cause of diarrhoea in infants, which can lead to severe dehydration
• MenB Vaccine: Administered at 8 weeks, 16 weeks, and one year, this vaccine protects against meningococcal group B bacteria
• Hib/MenC Vaccine: Given at one year of age, it boosts protection against Hib and protects against meningococcal group C bacteria
• MMR Vaccine: Given at one year and at around three years and four months, this vaccine protects against measles, mumps, and rubella
• 4-in-1 Pre-school Booster: Given at around three years and four months, this vaccine boosts protection against diphtheria, tetanus, pertussis, and polio
• HPV Vaccine: typically around the age of 12-13 to protect against human papillomavirus
• 3-in-1 Teenage Booster: Teenagers around 14 Yo, boosts protection against diphtheria, tetanus, and polio

Schedule Reasoning:

1) Age-Specific Disease Risk: Some diseases pose a particular risk at certain ages. E.g. pertussis and Hib is dangerous for young infants, hence vaccination is initiated at 8 weeks

2) Vaccine Effectiveness at Different Ages: MMR (measles, mumps, and rubella) vaccine is not usually given before the age of one year because babies have residual antibodies from their mother that can interfere with the immune response to the vaccine

3) Risk of Exposure: meningitis ACWY vaccine is given to teenagers and “fresher” university students because these groups are at higher risk of being exposed to these diseases

4) Response to Vaccine Boosters: For instance, the DTaP/IPV/Hib/HepB vaccine is given at 8, 12, and 16 weeks to boost the initial immune response and provide long-lasting protection

5) Combination Vaccines: Safe and reduce the number of injections needed.

Question 2

Describe the components of each vaccine, the type of vaccine, and why they work

Answer 2

1) Live Attenuated Vaccines:

• Weakened form of a pathogen, unable to cause disease under normal conditions
• Can elicit a strong and lasting immune response after a single dose in most cases by stimulating both cellular and humoral immunity
• Attenuated pathogen can still enter cells and be presented by MHC class 1 molecules, activating cytotoxic T cells
• Simultaneously, antigens can be presented via MHC class 2 molecules, activating helper T cells, which aid B cells in producing antibodies

2) Inactivated vaccines:

• Inactivated by heat or chemicals, safer than live but require multiple doses

3) Subunit, recombinant, polysaccharide and conjugated vaccines:

• Only parts of the virus or bacteria, or recombinant proteins
• Protein or sugar, strong immune response but require boosters

4) mRNA vaccines:

• Gives instructions to cells to produce a harmless piece of the virus, usually the spike protein
• This protein triggers an immune response, producing antibodies against the antigen of the virus

Question 3

Discuss how disease surveillance influences the implementation of vaccines

Answer 3

1) Identifying the need for vaccines:

• Disease surveillance continuously monitors disease trends, and identify which pose a significant threat to public, health and thus need to be controlled through vaccination

2) Determining Target Population:

• Disease surveillance can identify the demographic group most affected by a disease, which guides the targeting of vaccination campaigns

3) Evaluating Vaccine Effectiveness:

• A decline in disease incidence following vaccination indicates that the vaccine is effective
• by monitoring disease cases, it’s possible to identify if there are breakthrough infections among vaccinated individuals, which may indicate the need for booster doses or vaccine modification

4) Monitoring Vaccine Coverage:

• Surveillance systems also monitor vaccine coverage, i.e. the percentage of the population that has received the vaccine
• help identify areas or groups with low coverage that need to be targeted to increase the overall immunity in the population

5) Detecting and managing outbreaks:

• Surveillance can help detect disease outbreaks in areas with low vaccine coverage or in groups of non-vaccinated individuals
• Rapid detection of outbreaks allows for swift implementation of control measures, including targeted vaccination campaigns

6) Identifying vaccine safety concerns:

• monitoring for adverse events following vaccination and assessing whether these events are occurring at a higher rate than would be expected in the general population

7) Determining eradication and elimination of diseases:

• Surveillance can provide evidence for the eradication or elimination of diseases, as seen with smallpox, and almost with polio

Question 4

Explain, with examples, how vaccines are used to protect more vulnerable groups in society e.g. neonates, elderly, immunosuppressed, in pregnancy

Answer 4

1) Neonates:

• Newborns are particularly susceptible to infectious diseases due to their immature immune systems
• For instance, the Hepatitis B vaccine is often given at birth to prevent the baby from acquiring the disease from an infected mother or environment
• The BCG vaccine (for tuberculosis) is also often given at birth or shortly after in countries where TB is prevalent

2) Elderly:

• The immune systems of older individuals can weaken, making them more susceptible to certain diseases
• Vaccines against flu, pneumococcal disease, and shingles are routinely recommended for older individuals

-3) Immunosuppressed:

• Individuals with compromised immune systems, such as those with HIV/AIDS or those receiving chemotherapy, are at greater risk of infections
• Inactivated or subunit vaccines are used to provide protection
• For example, the pneumococcal and flu vaccines are recommended for these individuals

4) During Pregnancy:

• Some vaccines are recommended during pregnancy to protect both the mother and baby
• The pertussis (whooping cough) vaccine is recommended during each pregnancy to protect the newborn who is too young to be vaccinated
• The influenza vaccine is also recommended because pregnant women are at higher risk of complications from flu
• The antibodies produced in response to these vaccines cross the placenta and provide passive immunity to the baby during the first few months of life

5) Herd Immunity:

• Vaccination also indirectly protects vulnerable individuals through the concept of herd immunity
• If a large proportion of the population is immune to a disease, its spread is slowed or stopped, protecting those who cannot be vaccinated or for whom the vaccine is not effective