CLINICALLY RELEVANT VACCINE-VACCINE INTERACTIONS - A GUIDE FOR PRACTITIONERS

The need for combination vaccines has been recognised for many years. Many children must have 9 or 12 injections in their first year, which places a considerable burden on the child and the health service. Comb ination vaccines or simultaneously administered vaccines need to gener ate a protective immune response to all vaccine components that is equ ivalent to the response when administered separately. This is not alwa ys the situation. Many vaccines should not be administered together be cause of adverse reactions known as vaccine-vaccine interactions, a ph enomenon where one vaccine affects another vaccine, thus potentially c ausing loss of immunogenicity, loss of protective efficacy or inductio n of adverse reactions. It is important to remember that most vaccine- vaccine interactions are asymptomatic and may only be discovered when the immune status of the vaccine recipient is analysed or when the ind ividual is challenged by the microbe. The interactions may occur becau se of physical or chemical interactions within the vaccine formulation , interactions between live vaccines or immunological interference. Th is review summarises known vaccine-vaccine interactions that have been critically analysed and categorised based on their clinical importanc e.