Licensed combination vaccinesCombination or combined vaccineA vaccine that consists of two or more antigens in the same preparation (e.g., MMR, DTP). undergo extensive testing before approval by national regulatory authoritiesNational regulatory authority (NRA)The regulatory body that approves procedures to ensure that medicines, including vaccines, are of adequate safety and potency. The vaccine manufacturer is responsible for demonstrating that the vaccine batch produced meets the requirements, based on the test specifications given by the NRA. The NRA is also responsible both for the official vaccine lot release process, based on the data and information provided by the manufacturer and, eventually, for confirmatory testing. to assure that the products are safe, effective, and of acceptable quality.
Combination vaccines consist of two or more antigens in the same preparation. This approach has been used for over 50 years in many vaccines such as DTwP and MMR. Combination products simplify vaccine administration and allow for the introduction of new vaccines without requiring additional health clinic visit and injections.
Potential advantages of combination vaccines include:
- reducing the cost of stocking and administering separate vaccines;
- reducing the cost of extra health care visits;
- improving timeliness of vaccination (some parents and health-care providers object to administering more than two or three injectable vaccines during a single visit because of a child's fear of needles and pain, and because of concerns regarding safety);
- facilitating the addition of new vaccines into immunization programmes.
It is very important, however, that combination vaccines are carefully tested before introduction. For instance, adjuvantsAdjuvantA pharmacological agent (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, while keeping the injected foreign material to a minimum. in a combination vaccine could reduce the activity of one antigen and excessively increase the reactivity of another antigen. There could also be interactions with other vaccine components such as buffersBuffersSubstances that minimize changes in the acidity of a solution when an acid or base is added to the solution. Buffers are used in the manufacturing process of some vaccines., stabilizersStabilizersCompounds that are used to help vaccine maintain its effectiveness during storage. Vaccine stability is essential, particularly where the cold chain is unreliable. Factors affecting stability are temperature and pH. and preservatives.
With all combinations, manufacturers must therefore evaluate the potencyPotencyA measure of strength or immunogenicity in vaccines. of each antigenic component, the effectiveness of the vaccine components when combined to induce immunity, risk of possible reversion to toxicity, and reaction with other vaccine components.
No evidence exists that the administration of several antigens in combined vaccines overwhelms the immune system, which has the capability of responding to many millions of antigens at a time. Combining antigens usually does not increase the risk of adverse reactions. In fact, it can lead to an overall reduction in adverse reactions.
With all combinations, manufacturers must, however, evaluate the potency of each antigenic component, the effectiveness of the vaccine components when combined to induce immunity, risk of possible reversion to toxicity, and reaction with other vaccine components.
Can you identify which five antigens are included in the pentavalent vaccine DTwPHepBHib?
This pentavalent vaccine combines five ('penta') antigens in one formulation: diphtheria toxoid, tetanus toxoid, whole-cell pertussis, hepatitis B and Haemophilus influenzae type b.