An HIV vaccine cannot use a live or killed whole virus due to safety risks. Subunit vaccines using individual viral proteins may be safer, but developing an effective HIV vaccine faces major challenges. These include not knowing which immune response provides protection, the lack of a suitable animal model, HIV's ability to evade the immune system by integrating into human DNA, and interfering with immune responses. Proper nutrition, environment, vaccination administration and storage are also important for vaccine effectiveness.

1.  An HIV vaccine cannot consist of attenuated,
actively replicating (live) HIV, due
to possible reactivation.
 Killed whole virus (like the polio vaccine)
might also be dangerous because
one could not be sure one has killed all viral
particles. A killed whole virus
vaccine had also worked poorly in animal
studies.

2.  There were successful vaccines that use
subunits of viruses such as individual
proteins: an example was the hepatitis B
vaccine. However medical science
was less experienced with them.
 There is no truly useful small animal model
for studying HIV infection and
vaccines had to be developed in monkeys
using SIV (Siamin) or the artificial
monkey/human virus SHIV in monkeys, which
did not have exactly the same
immune effects as HIV.

3.  We do not know with certainty which
immune response will provide protection;
this is a major problem. Pre-efficacy studies
of vaccines in monkeys and
humans used correlates of immunogenicity
such as CD8 cell response, but we
do not know whether this immune response is
in fact a correlate of efficacy.

4.  We have never before attempted to develop
a vaccine against a retrovirus like
HIV. Retroviruses, by integrating their
genome into ours, are able to hide
completely from immune surveillance within
quiescent lymphocytes. This
means that any vaccine has a small window
of opportunity in which to prevent
infection and would have to be extremely
effective, repelling all attempts by
HIV to attach to and infect host cells.

5.  HIV produces viral proteins such as tat and vif
that actively interfere with what
would otherwise be a potent anti-HIV response in
both infected and uninfected
cells.
 CD8 cellular vaccines do not block infection
because they act at too late a
stage, so, if they worked, would do so by
reducing the viral load in chronic
infection. They would not necessarily reduce the
peak level of viraemia in the
early burst of viral reproduction and might not
control infections transmitted by
people in acute infection

6.  HIV is capable of developing immunity to the
CD8 cellular response.
 Many management factors can limit the
effectiveness of vaccination including
nutrition, environmental conditions,
exposure to disease, and vaccination
administration
 Protein, energy, minerals and vitamins are all
required to develop and maintain a strong
immune system

7.  Specific vitamins and minerals associated
with optimal immune function include
vitamin A, vitamin E, selenium, copper, and
zinc
 Harsh or stressful environmental conditions
can have significant detrimental effects on
immune function.
 In addition, crowding and poor sanitation
increase the exposure to infectious agents
which can overcome even high levels of
immunity.

8.  It is extremely important that we try to
maximize the benefits of vaccination by
proper use and administration.
 Two very common causes of vaccine failure
are inappropriate storage and
administration.
 Most vaccines should be stored in the
refrigerator and may loose their
effectiveness within 12 hours of storage at
room temperature or less than one hour in
extreme heat or direct sunlight.

9.  Vaccines that require mixing prior to use are
usually only good for 12 hours or less.
 Vaccines are an important management tool
in preventing infectious diseases, they have
their limitations.