35 Protecting the host: vaccination Flashcards
Vaccination aims to prime adaptive immune system, so second contact will provide a rapid and effective secondary immune response by memory T and B cells.
What are different types of vaccines and examples?
Live attenuated -
- viral - measles, mumps, rubella, vaccinia, varicella, yellow fever, zoster, oral polio, intranasal influenza, rotavirus
- bacterial - BCG, oral typhoid
Inactivated -
- Whole virus - polio, influenza, hepatitis A, rabies, JE
- Whole bacteria - pertussis, cholera, typhoid
Fractions -
- toxoids - diptheria, tetanus
- protein subunits - hepatitis B, influenza, pertussis, HPV 6/11/ 16/ 18
- polysaccharides - pneumococcal, meningococcal, salmonella typhi, Hib
- conjugates - pneumococcal, meningococcal, Hib
Who should not be given live vaccines?
HIV patients
Pregnant
Inactivated vaccines are safe to use
Why are toxoid vaccines used for diptheria/ tetanus?
It is the toxin which is damaging to host, not the bacteria itself. So use inactivated toxoid as vaccine
Inactivated/ protein/ polysaccharide require multiple doses for vaccination. Why is this?
Less immunogenic than vaccines with whole organisms.
Sometimes adjuvants are required to improve immune response through inducing activation of Toll-like receptors on dendritic cells to improve antigen presentation. Certain chemicals can be used as adjuvants, such as aluminium salts, and cytokines IL1, IL2, IFNgamma can help boost immune response
What are problems with vaccine safety?
Live attenuated -
- insufficient attenuation
- reversion to wild type
- admisiter to immunodeficient patient
- contamination other viruses
- foetal damage
Non-living vaccines
- contamination by chemicals
- allergic reaction
- auto-immunity
Why are childrens vaccinations required to be repeated?
Can have maternal antibodies, so do not develop own memory cells
Some vaccines are less immunogenic
What are the two types of polio vaccine?
Three serotypes of polio, vaccine works against all three - trivalent.
But polio-2 and polio-3 has been eliminated, so may only need to use monovalent vaccine in future
Inactivated IPV - Salk 1954
Injectible
Risk if inadequatley killed
Attenuated OPV - Sabin 1957
Oral - easy to administer
Benefits - replicates in intestine produce local immunity IgA, and can be spread to other household members.
Risk of vaccine associated paralytic polio (VAPP)
they both target polio virus 1/ 2/ 3
What are risks of oral polio vaccine? OPV
Can can vaccine associated paralytic polio (VAPP)
OPV virus can be transmitted in community termed circulating vaccine-derived polio viruses cVDPV. If susceptible population, can survive moving between hosts. Mutations slowly develop, and cause paralysis
Why was it difficult to create pneumococcal vaccine?
over 90 serotypes
Most common 23 serotypes included in vaccine
Why does haemophilus vaccine target type b serotype?
six capsular serotypes, but type b causes 95% of disease.
Usually those under 5 affected
Why is influenza vaccine difficult to develop?
Influenza vaccine contains three flu strains -
2 A strains
1 B strain
Antigenic drift - gradual mutation
Antigenic shift - reshuffle of RNA can produce different H/N antigens
Given to people >65 who have weaker immune systems, so may not generate sufficient immune response - immunosenescence
Winter 2020-21
H1N1
H3N2
B
Why is it difficult to produce HIV vaccine?
gp120 can mutate easily
killed virus not sufficiently immunogenic
route of infection via genital tract, means need localised mucosal immunity, which vaccine can’t provide
Adenoviruses are useful as vaccine vectors, why is this?
What are draw backs?
Induce good CD8 T cell response
Some people have already been infected with adenovirus species, and have antibodies to them, so may not generate good immune response
Why was smallpox easy to erradiacte?
highly effective vaccine
Easy to administer vaccine
Single vaccine dose
Infected patients can be easily spotted
Easy to contain patients once diagnosed
Permanent immunity after disease/ vaccination
No animal reservoir
When targeting next disease for erradication, what factors must be present?
Humans must be critical to circulating organism - no animal reservoir
Sensitive/ specific diagnostic tools
Effective vaccine
Why is there a problem with developing a dengue vaccine?
Antibody dependent enhancement between serotypes
Antibodies generated during primary infection with one serotype of virus will not be sufficient to neutralise a second serotype.
However, they might be able to opsonise the secondary virus, and target it for phagocytes. This can lead to dengue haemorrhagic fever or severe dengue on repeat infection
How are organisms inactivated for vaccination?
heat
Chemicals
radiation
some patients have egg allergy. Which vaccine should you seek alternative?
4CMenB DTaP/ PIV/ Hib Influenza MMR Q fever Rotavirus Yellow fever Rabies
Influenza uses embryonated eggs - can use intranasal vaccine instead.
Yellow fever contains eggs and should be avoided
Rabies uses egg embyros and should be avoided
Q fever uses egg embryos and should be avoided
MMR produced in eggs, but is safe as long as no anaphylaxis, as no egg free alternative available
discuss with immunologist if require to give vaccination
VZV susceptible healthcare worker on oncology ward receives varicella vaccine dose through occupational health. She presents two weeks later with vesicular rash. Otherwise well. Not pregnant.
What is next management?
Avoid patient contact until lesions crusted over
<5% develop vesicular rash 5-26 days after vaccination. Given her rash is after two weeks, then it is less likely to be caused by vaccine, and may be new VZV infection.
In any case, vaccine strain is sensitive to aciclovir
- viral PCR of lesion
- viral genome analysis, to see if wild type. Serology does not help differentiate the two
Which vaccines are live attenuated?
Live attenuated -
- viral - measles, mumps, rubella, vaccinia, varicella, yellow fever, zoster, oral polio, intranasal influenza, rotavirus
- bacterial - BCG, oral typhoid
