Vaccines

Question 1

Maternal IgG protects new born babies

When do levels of this start to decline?

Answer 1

By about 9 months most maternal IgG is lost

If testing IgG in baby, by 18months you can be certain any IgG present is the baby’s

Question 2

Do vaccines prevent infection or disease?

Answer 2

Primarily prevent disease, or reduce disease severity

Can prevent infection. If have robust and quick immune response, can stop infection getting hold

Vaccines can also be given as post-exposure prophylaxis. Goal is to attenuate disease, so cannot stop infection

Question 3

How many people need to be vaccinated to induce herd immunity?

Answer 3

Depends on the virus. Usually between 80-95% is enough to reduce the number of susceptible hosts, and stop virus in its tracks

Remember that no vaccine is 100% effective the level of immunity is not equal to
the number of people immunized. In fact, we know that when 80% of a population is immunized with measles vaccine,
about 76% of the population is actually immune, clearly well below the 95% level to prevent Measles

Question 4

What are the four main types of vaccine?

Answer 4

Inactivated - via chemical means

live attenuated - can replicate

subunit vaccine - portion of the virus e.g HBsAg

recombinant - clone selected viral proteins into non-pathogenic bacteria/ yeast to produce immunogenic protein