Penta- and hexavalent vaccination of extremely and very-to-moderate preterm infants born at less than 34 weeks and/or under 1500 g: A systematic literature review.

Combined vaccines such as penta- and hexavalent vaccines against multiple childhood diseases are widely used in healthy babies born at term. However, it is still debated whether these vaccines act the same way in babies considered to be high-risk: babies born prematurely at <34 weeks of pregnancy, those with a birthweight of <1500 g or babies with chronic diseases. We did a systematic literature search to find studies on such high-risk babies vaccinated with penta- or hexavalent vaccines; we focused on their antibody levels following vaccination, side effects, and protection from the diseases against which they were vaccinated. We also analyzed whether they were vaccinated on time and with all the doses recommended for healthy full-term babies. We found 14 studies that included premature babies. The results of these studies suggest that premature babies' immune systems respond to penta- and hexavalent vaccines in largely the same way as those of full-term babies; side effects of penta- and hexavalent vaccines are also mostly similar to those seen in full-term babies. However, side effects like pauses in breathing, slow heart rate or low blood oxygen levels seem to be more common in preterm babies; for safety, these babies should be monitored closely after vaccination. Preterm babies are often vaccinated with a delay compared to the recommended schedule. No studies reported data on protection from the diseases covered by penta- and hexavalent vaccinations in preterm babies. More research is needed on penta- and hexavalent vaccination of other high-risk babies besides those born prematurely.