Vaccination Order for Pneumococcal Conjugate Vaccine May Affect Infant Pain Response

From Medscape Medical News
Laurie Barclay, MD

May 5, 2009 — Infants who receive the pneumococcal conjugate vaccine (PCV) after the combination vaccine for diphtheria, polio, tetanus, pertussis, and Haemophilus influenzae type b (DPTaP-Hib vaccine) appear to experience less pain than those who are immunized in the reverse order, according to the results of a double-blind, randomized clinical trial reported in the May issue of the Archives of Pediatric & Adolescent Medicine.

"Vaccine injections are the most common painful iatrogenic procedures performed in childhood," write Moshe Ipp, MBBCh, from the University of Toronto in Toronto, Ontario, Canada, and colleagues. "Multiple injections are routinely administered during a single visit to a physician....The objective of this study was to determine if acute pain response after administration of 2 separate vaccines was affected by the order in which they were administered."

At an outpatient pediatric clinic in Toronto, Ontario, Canada, healthy infants aged 2 to 6 months who were undergoing routine immunization received either their primary DPTaP-Hib vaccine or the PCV first, followed by the other vaccine. The main endpoint of the study was infant pain during vaccine injection as measured by a validated measure, the Modified Behavioral Pain Scale (MBPS), with use of videotaped recordings of the vaccination. Other outcomes were parent-rated pain with use of a 10-cm visual analog scale (VAS) and the presence or absence of crying.

Between July 21, 2006, and June 21, 2007, a total of 120 infants participated, of whom 60 received the DPTaP-Hib vaccine first and 60 received the PCV first. The groups did not differ significantly in infant characteristics.

When DPTaP-Hib was given first, overall mean pain scores per infant after receiving both vaccine injections were significantly lower than when PCV was given first (MBPS score, 7.6 ± 1.5 vs 8.2 ± 1.5; P = .037; parent VAS score, 4.2 ± 2.3 vs 5.6 ± 2.6; P = .003). Based on the MBPS, VAS, and crying, the DPTaP-Hib vaccine caused significantly less pain when given first (P < .001).

"Pain was reduced when the DPTaP-Hib vaccine was administered before the PCV in infants undergoing routine vaccination," the study authors write. "We recommend that the order of vaccine injections be the DPTaP-Hib vaccine followed by the PCV."

Limitations of this study include relatively small sample size and difficulty in assessing pain in infants.