Question

A. Most clinical trials for vaccines evaluate the risks/adverse reactions associated with the use of an adjuvant in a vaccine on healthy people. However, when approved the vaccine may be given to elderly or sick individuals. Is repeated doses of the adjuvant containing vaccine likely to increase the risk of observing adverse reactions in a given individual? Why or why not? (Hint: think about the annual flu shot.)

B. Why are multiple vaccine doses still needed even if an adjuvant is present in the vaccine?

Answer 1

Adjuvants may act by a combination of various mechanisms including formation of depot, induction of cytokines and chemokines, recruitment of immune cells, enhancement of antigen uptake and presentation, and promoting antigen transport to draining lymph nodes. It appears that adjuvants activate innate immune responses to create a local immuno-competent environment at the injection site. Depending on the type of innate responses activated, adjuvants can alter the quality and quantity of adaptive immune responses. Understanding the mechanisms of action of adjuvants will provide critical information on how innate immunity influences the development of adaptive immunity, help in rational design of vaccines against various diseases, and can inform on adjuvant safety.

Newer adjuvants have been developed to target specific components of the body’s immune response, so that protection against disease is stronger and lasts longer.

In all cases, vaccines containing adjuvants are tested for safety and effectiveness in clinical trials before they are licensed for use in the United States, and they are continuously monitored by CDC and FDA once they are approved.

Common local reactions to vaccines include pain, swelling, and redness at the injection site. Systemic reactions, including fever, irritability, drowsiness, and rash, may also occur. The administration of acetaminophen at the time of vaccination or shortly afterward may moderate these effects.

Compared with the first dose, the fourth dose of currently licensed diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP) has been associated with increased incidences of fever and erythema, swelling, and pain at the injection site. In a small percentage of children, swelling of the entire thigh or upper arm for about four days has been reported after the fourth or fifth dose of DTaP.

Minor reactions

Usually occur within a few hours of injection.

Resolve after short period of time and pose little danger.

Local :-Local (or localized)Restricted or limited to a specific body part or region. (includes pain, swelling or redness at the site of injection).

Systemic :-SystemicRelating to a system, or affecting the entire body or an entire organism (e.g., fever). (includes fever, malaise, muscle pain, headache or loss of appetite).

Severe reactions

Usually do not result in long-term problems.

Can be disabling.

Are rarely life threatening.

Include seizures:- Uncontrolled electrical activity in the brain, resulting in convulsion, physical signs, thought disturbances, or a combination of symptoms. and allergic reactions caused by the body's reaction to a particular component in a vaccine.

In addition, other vaccine components (e.g., aluminum salt, oil-in-water emulsions) that modifies the effect of other agents, such as a drug or vaccine, while having few if any direct effects when given by itself. Adjuvants are often included in vaccines to enhance the recipient's immune response to a supplied antigen. It can trigger reactions. A successful vaccine keeps even minor reactions to a minimum while producing the best possible immune response

The frequency of vaccine reactions likely to be observed with some of the most commonly used vaccines, and their treatments, are listed below. These reactions typically occur within a day or two of immunization (except for rash reactions after measles vaccine, which can arise up to 6 to 12 days after immunization) and persist from one to a few days.

First, children should be given their vaccines as quickly as possible to give them protection during the vulnerable early months of their lives. Second, giving several shots at the same time means fewer office visits. This saves parents time and money, and can be less traumatic for the child.