Change In Vaccine Order Affects Infants' Response To Pain

By Margarita Nahapetyan

Canadian doctors say that the certain order in which vaccine injections are being administered to infants, affects their response to pain. According to scientists, infants who receive the pneumococcal conjugate vaccine (PCV) following the combination vaccine for diphtheria, polio, tetanus, pertussis and Haemophilus influenzae type b (DPTaP-Hib vaccine), appear to experience less pain compared to those who receive immunization in the opposite order.

"To our knowledge, the effect of varying the order in which vaccines of different degrees of painfulness are given has not been previously examined," said Dr. Moshe Ipp, M.B.B.Ch., from The Hospital for Sick Children in Toronto. The findings of his new study suggest that when two vaccines are to be given, the less painful one - in this case DPTaP-Hib - should be given first, before the more painful one - in this case PCV.

To come up with this conclusion, Dr. Ipp and his colleagues studied 120 healthy infants with the ages between 2 and 6 months, who underwent routine immunization procedure at a outpatient pediatric clinic in 2006 or 2007. Fifty per cent of the infants received the pneumococcal vaccine before DPTaP-Hib, while the other half were administered DPTaP-Hib vaccine first. The injections were given in the thigh muscles.

The procedure of immunization was videotaped and the pain level of infants was assessed using a scale that measured the facial expression of the baby, their crying and body movements after vaccination. According to Dr. Ipp, the videotape records allow to see in a slow motion a change in the child's face when they have pain. He explained that first, a child's mouth starts to open, then they close their eyes, furrow their brows and finally, they get agitated and the whole body starts to move as they begin to cry. Parents were also asked to rate their child's pain levels on a scale of zero to ten.

The study found that the infants who were given the less painful combined vaccine DPTaP-Hib first, followed by the more painful PCV vaccine, expressed about 25 per cent less pain compared to those babies whose initial injection was for the pneumococcal vaccine. Researchers said that this was seen with both the pain scale and the parents' assessment.

As to why the order of immunizations affects the pain response, the scientists suggest that when the more painful injection is given first, it focuses the child's attention on the procedure and activates pain processing mechanisms in the brain that together lead to amplification of the pain signal during the following injections that are given immediately thereafter.

Injections are the most painful common medical procedure that is performed in childhood, say the investigators, who are seeking the ways to relieve the pain and discomfort of vaccinations that are used to prevent a host of infectious diseases. Reducing pain from vaccinations in children is also important because, according to the findings of another recent survey by U.S. pediatricians, more than 90 per cent reported that, at least one parent in their practice had refused to have a child vaccinated in the previous year, most commonly because of pain caused by multiple immunizations.

The other recommendations that researchers have for doctors and nurses include:

• Giving a vaccine as fast as possible without pulling back on the plunger.

• Immunizing infants under the age of 12 months in the thigh, and using the arm for older children, who complain and limp less when it is being administered that way.

• Applying a topical anesthetic on the area of injection or giving a sugar solution, in particular to newborns.

• Distracting children, and asking a parent to hold them.

The report is published in the May issue of the Archives of Pediatrics & Adolescent Medicine journal.