VACCINES
PETER H. RUSSELL, BVSc,
PhD, FRCPath, MRCVS
Department of Pathology and
Infectious Diseases, The Royal
Veterinary College,
Royal College Street,
London NW1 OTU.
E-mail Web site
Objectives
Students should be able to:
• summarise the mechanisms of primary and
secondary immune responses to virus
infections and to vaccines.
• compare and contrast different types of
vaccine with some veterinary examples.
• describe the influence of maternal antibody on
vaccination outcome.
• list some of possible reasons for the failure of
vaccines to protect against disease.
Vaccination involves setting up
memory to the virus infection such that
a high level of cytotoxic T cells (Tc)
and IgG are activated in 1-2 days
instead of 4-10 days. These curtail the
infection before lesions develop.
IgA/IgG at mucosal surfaces are also
useful to neutralise virus before entry
but is difficult to achieve except by
mucosal live vaccines.
The mechanisms of recovery
from a primary infection will first
be reviewed
The mechanisms of recovery
from a primary infection will first
be reviewed
(cont.)
The mechanisms of recovery
from a primary infection will first
be reviewed
(cont.)
Reasons for a failure to recover
Vaccination
Types of field vaccine
Maternal antibody and vaccination
Reasons for vaccine failure
Types of field vaccine:
1) live (attenuated)
2) inactivated
3) subunit
4) recombinant
5) DNA vaccines, research
1) Live (attenuated)
1) Live (attenuated)
(cont.)
2) Inactivated vaccines
3) Subunit vaccines
4) Recombinant live vaccines
5) DNA vaccines, research
Maternal antibody and
vaccination
Maternal antibody and
vaccination
(cont.)
Reasons for vaccine failure.
SUMMARY
Vaccines are used for endemic diseases which may then become
so rare vaccination can cease
Vaccines induce memory for Tc and VN IgG/IgA but without the
risk of disease.
Most commercial vaccines are either inactivated or live-
attenuated with the exception of the recombinant FeLV from
E.Coli.
Inactivated vaccines are more expensive to produce and often
administered with adjuvants
Vaccines must be quality controlled
The vaccination programme must allow for maternal antibody
Vaccines can fail, most usually because of new challenge viruses
with altered antigens or increased virulence.