I kliniske forsøg, hvor nogle af de vaccinerede fik Infanrix hexa samtidig med Prevenar som en boosterdosis (4. dosis) af begge vacciner, blev feber ≥ 38 °C set efter 43, 4% af dosis hos børn, som fik Prevenar og Infanrix hexa samtidig, sammenlignet med 30, 5% af dosis hos børn, som fik den hexavalente vaccine alene.
In clinical studies in which some of the vaccinees received Infanrix hexa concomitantly with Prevenar as a booster (4th) dose of both vaccines, fever ≥ 38.0°C was reported following 43.4% of doses in infants receiving Prevenar and Infanrix hexa at the same time as compared to 30.5% of doses in infants receiving the hexavalent vaccine alone.