Preemies Mount Adequate Response to Most Routine Vaccines

By Reuters Staff

September 16, 2020

NEW YORK (Reuters Health) - New research shows that administering routine vaccines during the first year of life to infants born prematurely leads to protective antibody levels of most antigens in most infants after the primary series and booster, with the exception of Haemophilus influenzae type b.

However, in general, antibody concentrations are generally lower in preemies compared with term babies.

While some countries adjust their primary vaccination schedules in cases of prematurity, most, including the Netherlands and the United States, use the same primary schedule and timing for all newborns, Dr. Elsbeth Rouers and colleagues of the National Institute for Public Health and the Environment, in Bilthoven, the Netherlands, note in JAMA.

To see if the standard schedule of national immunization programs for infants is sufficient to protect extremely and very preterm infants, they studied 296 preterm infants (87 born at less than 28 weeks gestational age, 119 born between 28 and less than 32 weeks and 90 born between 32 and 36 weeks of age) and 66 historical-control infants born at term.

Three primary doses of the diphtheria-tetanus toxoids-acellular pertussis-inactivated poliomyelitis-Haemophilus influenza type b-hepatitis B (DTaP-IPV-Hib-HepB) combination vaccine were given at 2, 3 and 4 months after birth, followed by a booster at 11 months. The 10-valent pneumococcal conjugate vaccine (PCV10) was administered at 2, 4 and 11 months.

Following the primary series, the proportion of preterm infants across all gestational age groups who achieved protective IgG antibody levels against pertussis toxin, diphtheria, tetanus and six of 10 pneumococcal serotypes varied between 83% and 100%.

However, protective IgG antibody levels for Haemophilus influenzae b were achieved in only 40.6% of preterm infants and for pneumococcal vaccine serotypes 4, 6B, 18C and 23F in only 45.8% to 75.1% of infants, "which is significantly lower than in term infants," the researchers report.

"The high proportion of unprotected preterm infants against Haemophilus influenzae type b until the booster dose may have clinical implications if herd protection is low and should be considered when advising on national immunization schedules for preterm infants. An additional booster vaccination after the primary series might be needed, but further research to evaluate this is necessary," they write.

Following the booster dose, protective antibody levels were achieved in more than 95% of all preterm infants, except for Haemophilus influenzae type b (88.1%).

"Preterm infants born before 28 weeks' gestational age had the highest risk for lack of protective antibody levels after polysaccharide conjugate vaccinations," the researchers note.

"For extremely preterm infants, good data on vaccine responses have been lacking due to, among other reasons, difficult enrollment of this group," the authors note. "This study was adequately powered to evaluate vaccine responses in preterm infants by gestational age and is, to our knowledge, the most comprehensive analysis of vaccine immunity in preterm infants to date."

"The availability of a historical control group of term infants who received the same vaccines in a similar schedule for comparison is another strength of this study. As current clinical practice of immunizing preterm infants was followed, results should be generalizable to preterm infants in similar communities," they conclude.

Dr. Rouers did not respond to a request for comment by press time.

The study was funded by the Dutch Ministry of Health, Welfare, and Sport. The authors have no relevant conflicts of interest.

SOURCE: online September 15, 2020.