L38: Fever and rash - vaccines

Question 1

Taking a vaccination history

Answer 1

(UTD = up to date)

• Important to know schedule and age patient got them
• Place of birth, have they been overseas
• Aware of present outbreaks

Question 2

Classification of vaccines

Answer 2

Live attenuated vaccine: either live viruses or live bacteria e.g. MMR is live bacterium

Inactivated vaccines: whole viruses or bacteria, or fractions of either (fractional are protein or polysaccharide based)

• Protein-based include toxoids and subvirion products (e.g. tetanus)
• Recombinant vaccine e.g. hep B
• Polysaccharide-based e.g. pneumonococcal
• Conjugate polysaccharide (polysaccharide linked to a protein) e.g. conjugate pneumococcal

Question 3

Measles

Answer 3

• Highly infectious
• 2-3 days fever, conjunctivitis, coryza, Koplicks spots (mouth)
• Characteristic rash day 3-7
• Complications common = 10% secondary infection (ear, pneumonia, croup), encephalitis, subacute sclerosing pancencephalitis (v. rare, degenerative fatal nervous disease)

Vaccination: at 15months, 4yrs in the MMR (measles, mumps, rubella)

Question 4

Mumps

Answer 4

• Most cases between 10-29yrs

- Complications: meningoencephalitis, orchitis, oophritis

Question 5

Bacterial meningitis

Answer 5

= inflammation of meninges (membrane surrounding brain)

• Caused by: S. pneumoniae, N. meningitidis, Haemophilus influenzae (rare due to vaccination)
• Newborns: Grp B streptococcus, gram negative (E. coli)
• Viral agents can also cause meningitis and encephalitis too (herpes simplex virus and enterovirus)
• TB can also cause meningitis
• Hearing loss most common complication of meningitis in infancy

Question 6

Polysaccharide vaccines

Answer 6

• Polysaccharide-based inactivated vaccines are composed of pure cell wall polysaccharide from bacteria e.g. pneumococcal polysaccharide vaccine
• Young children <2yrs produce v. weak antibody response to polysaccharide antigens = poor immunological memory

Question 7

Conjugate vaccines

Answer 7

• Conjugate polysaccharide vaccines: polysaccharide chemically linked to a carrier protein e.g. conjugate pneumococcal vaccine
• Taken up by B cells
• Carrier protein digested and antigen presented to helper T cells
• Converts T cell-independent carbohydrate antigen into T cell-dependent antigen
• Good immunogenicity in those <2yrs
• Good production of memory cells

Question 8

Haemophilus influenzae type B (Hib)

Answer 8

• Serious disease almost eradicated by immunisation in developed world
• Gram-neg bacilli (rod)
• Typed by capsule

Hib vaccine

• Induce antibodies to capsule (PRP polysaccharide)
• Initial vaccine unconjugated and poorly immunogenic
• Now conjugated: effective in young infants and at stopping carriage
• Given at 6wks, 3mths, 5mths and 15mths
• Protected efficacy is 98%
• Do not need booster after early childhood as adults do not get it

Question 9

S. pneumoniae

Answer 9

• Gram-positive coccus, polysaccharide external capsule
• Over 90 serotypes based on different capsular polysaccharides
• Colonises nasopharynx in 10% of adults, 30% of children
• Invasive disease common in <5yrs or >65ys (bacteraemia, pneumonia, otitis media, sinusitis)

Question 10

Invasive pneumococcal disease

Answer 10

• Pneumococci isolated from usually sterile sites: CSF (meningitis), blood (bacteraemia), lung tissue/pleural space (pneumonia)
• Major cause of morbidity and mortality in children <2yrs
• Most common bacterial cause of otitis media in children
• Most common cause of bacterial pneumonia in all age groups

Question 11

Vaccination for S. pneumoniae

Answer 11

= polysaccharide vaccine

• Contains capsular polysaccharide from each of 23 most common serotypes
• Used in splenectomy, immunosuppressed, chronic illness
• Elderly (>65yrs, recommended but not funded)
• Not useful for less than 2yrs old
• PCV10 vaccine at 6wks, 3mths, 5mths, 15mths
• 97% efficacy against IPD caused by vaccine serotypes
• Protection for those not receiving vaccines (older children and adults) = herd immunity

Question 12

Neisseria meningitidis

Answer 12

• Polysaccharide capsule important virulence factor
• Exclusive human pathogen, transmitted by droplets
• 12 serotypes based on capsular polysaccharide (A, B, C most common and sometimes W135 and Y)
• Antibodies important in protection
• A, B, C can cause epidemics and W135 rising in NZ
• Polysaccharide capsule of B composed of same sugars as those found on surface of human immature neural cells (so lymphocytes that could produce antibodies to capsule are deleted during fetal development)

Question 13

Vaccines for meningococcal disease

Answer 13

• NZ MenzB vaccine (no longer used) used outer membrane inside polysaccharide capsule - not lasting antibodies but reduced epidemic)
• Both purified capsular polysaccharides and conjugate protein vaccines for A, C, W135, Y
• Meningococcal C conjugate vaccine on schedule in Aus and UK and can buy in NZ
• New MenB vaccine on schedule in UK (uses 4 target proteins of serogroup B strain)

Question 14

Common reasons for not immunising

Answer 14

• Contraindications for immunisation
• Barriers to access to healthcare
• Lower immunisation access and rates for Maori children improved with recall/outreach programmes in primary care (Tamariki Ora, kaupapa Maori)

Question 15

Trends in immunisation

Answer 15

• Target of 95% full immunised at 2yrs attained by many DHBs
• New target is timeliness (area of challenge is Maori and deprivation)
• Challenges in maintaining systems
• At 2yrs old coverage is 90% (less disparities between ethnic groups, SEP)