Vaccines do not guarantee complete protection from a disease. Sometimes this is because the host's immune system simply doesn't respond adequately or at all. This may be due to a lowered immunity in general (diabetes, steroid use, HIV infection) or because the host's immune system does not have a B cell capable of generating antibodies to that antigen.
Even if the host develops antibodies, the human immune system is not perfect and in any case the immune system might still not be able to defeat the infection.
Adjuvants are typically used to boost immune response. Most often aluminium adjuvants are used, but adjuvants like squalene are also used in some vaccines and more vaccines with squalene and phosphate adjuvants are being tested.
The efficacy or performance of the vaccine is dependent on a number of factors:
- the disease itself (for some diseases vaccination performs better than for other diseases)
- the strain of vaccine (some vaccinations are for different strains of the disease) [http://bmj.bmjjournals.com/cgi/content/full/319/7206/352
- whether one kept to the timetable for the vaccinations
- some individuals are 'non-responders' to certain vaccines, meaning that they do not generate antibodies even after being vaccinated correctly
- other factors such as ethnicity or genetic predisposition
When a vaccinated individual does develop the disease vaccinated against, the disease is likely to be milder than without vaccination.
The following are important considerations in the effectiveness of a vaccination program:
- careful modelling to anticipate the impact that an immunization campaign will have on the epidemiology of the disease in the medium to long term
- ongoing surveillance for the relevant disease following introduction of a new vaccine and
- maintaining high immunization rates, even when a disease has become rare.
In 1958 there were 763,094 cases of measles and 552 deaths in the United States. With the help of new vaccines, the number of cases dropped to fewer than 150 per year (median of 56). Disputes have arisen over the morality, ethics, effectiveness, and safety of vaccination. The mainstream medical opinion is that the benefits of preventing suffering and death from serious infectious diseases greatly outweigh the risks of rare adverse effects following immunization. Some vaccination critics say that vaccines are ineffective against disease or that vaccine safety studies are inadequate. and some political groups oppose mandatory vaccination on the grounds of individual liberty.
Most vaccine development to date has relied on 'push' funding by government, universities and non-profit organizations. Many vaccines have been highly cost effective and beneficial for public health. may be due to government mandates and support, rather than economic incentive.
Many researchers and policymakers are calling for a different approach, using 'pull' mechanisms to motivate industry. Mechanisms such as prizes, tax credits, or advance market commitments could ensure a financial return to firms that successfully developed an HIV vaccine. If the policy were well-designed, it might also ensure people have access to a vaccine if and when it is developed.
Further Reading
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