Sayenna Uduman*, M I Sahadulla**, Raja Lakshmi***, Pretty G tharakan****
General principles of combination vaccines (combos’)
• The decision to implement using the combos’ into immunization schedules involves, complex economic and logistical considerations.
• Vaccine provider should discuss with the parents on vaccine safety & availability, interchangeability and whether the patient is likely to return for follow up.
• Combos could be adopted in the recommended immunization schedule and should not be used outside the age groups for which they are licensed.
• Should use only those combinations that have been demonstrated to be safe and efficacious that are authorized for use.
• Combos are preferred over separate injections of the single component vaccines to keep the number of injections to a minimum.
• Can be used for children who have fallen behind the schedule (lapsed immunization schedule).
• Vaccines that are intended for separate administration should never be combined by vaccine providers. (i.e. PCV13 always to be administered separately )
• Vaccine Information Statement (VIS’s) on each vaccine components of the combos should be known and available for any or all of the routine vaccines given from birth-6 months (DTaP, IPV, Hib, PCV, rHepB )
• Should observe the nomenclature for combo’s contain either hyphens (-) or, sometimes, a forward ( / ) slash that are intended to indicate that the antigens are mixed (-) together by the manufacturer before the product is sold and the forward slash (/) indicates that the two products are to be reconstituted by the user.
• Switching between combination and single-antigen vaccines poses no problem as long as the recommended minimum intervals for all vaccines are maintained.
• For example, if a child is given separate DTaP, IPV, rHepB- Hib –PCV13 vaccines during 2-month ( or 6 to 8 week ) visit, combo’s of either DTaP-IPV/Hib (Pentacel) with a separate two additional shots are be given for rHepB & PCV13 OR a DTaP- rHepB-IPV (Pediarix) combo given, child need separate shot of Hib & PCV13 has to be given at the 4-month (14 to 16 week) visit.
• And, these days, more and more new combos are being introduced – and depending on the preference of your pediatrician, your child might be in line for one or more of these combos choices.

Efficacy of combination vaccines
The efficacy of each component in a combos’ is compared with established parameters of protection before product was authorized for immunization purposes. Antibody responses to specific antigens in combination products may be either stronger or weaker than responses to separately administered single antigens, but these differences are not considered to have any clinical impact.

Safety of combination vaccines
Prior to authorization, combos goes through careful testing to make sure the products are as safe and effective as each of the individual vaccines given separately. There may be differences in minor adverse events compared to single component vaccines, but they are not considered to be clinically significant and do not cause any lasting damage. In case of an adverse event following immunization, determining which component of a combination vaccine is responsible may be more challenging than in single component vaccines.

Potential advantages & benefits of combos
Simplifying immunization schedules by combining multiple vaccines into a single syringe has been reported to have numerous positive effects. A US study reporting increased coverage rates with a pentavalent DTaP- rHepB-IPV (Pediarix) vaccine than with multiple lower-valent vaccines containing the same antigens. The combos’ benefit includes:
• Fewer injections and reduced trauma to the infant
• The Hexavalent (DTaP-rHepB – IPV / Hib ) is especially exciting; since that might be just 2 shots for a child during infancy (Hexavalent and PCV13) visit for immunization.
• Higher rates of compliance with complex vaccine schedule & a better vaccine coverage.
• Timely vaccination- vaccination schedule are completed on time.
• Reduced administration cost and lower storage space requirement.
• Allows incorporation of new vaccines in the immunization schedules i.e. varicella vaccine incorporated with MMR( e.g.MMRV).
• reduced risk of injury to vaccine providers related to multiple injections of separate vaccines.

Future of Combo Vaccines
• Now, the ACIP recommending Hexavac (DTaP-rHepB-IPV / Hib) vaccine is especially exciting, since that might be just 2 shots for your child during infancy (Hexavac and PCV13).
• Other good combinations might include putting PCV & Hexavac together. That would mean just one shot at 2, 4 and 6 months!
Fewer shots are good, but even more exciting would be the development of edible vaccines. Early research showed that producing edible vaccines is theoretically possible, but the production of the first edible vaccines are likely way off.

Combos are necessary and important for success of our immunization program, especially when more vaccines are added to the already crowded immunization schedule. The recommended vaccines have been shown to be as effective in combination as they are individually, but further progress in this direction is warranted. Combo’s can help overcome some of the key challenges to maintaining coverage through universalization of vaccine schedules. To conclude, this is not the end of the story, as other waiting candidate vaccines for the newly emerging diseases, one day will need to be added to the combos' used.


Contributor Information and Disclosures

Sayenna Uduman*, M I Sahadulla**, Raja Lakshmi***, Pretty G tharakan****
Visiting Professor, Infection Control Committee & ID Division of the KIMS
Thiruvananthapuram, Kerala, India

**CMD, ID Division, KIMS
***ID Consultant, KIMS
****Clinical Pharmacist, KIMS

First Created : 3/11/2016


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