Introduction:
According to AAP (1992–1998), CDC (2009), and Polish (2015) recommendations, children before 37 weeks of pregnancy should be included in the same vaccination schedule as full-term newborns. It means that these infants should receive vaccinations according to the chronological age. This applies to newborns and infants born with small (< 2500 g), very small (< 1500 g), and extremely low body weight (< 1000 g), as well as children with a maturity of ≤ 33 gestational weeks. Although many studies indicate an immature immune system of this group of children, even those born with maturity below 29 weeks of gestation and those with bronchopulmonary dysplasia induce sufficient immune response to vaccinations. Neither body mass nor maturity are factors in limiting the schedule of recommended vaccination.

The aim of the study:
was to evaluate the implementation of vaccinations in the tertiary and secondary neonatal departments in the Mazovia region in the years 2015-2016 in newborns born before ≤ 33 weeks of pregnancy.

Material and methods:
Vaccination against pneumococci (PCV), pertussis, tetanus, diphtheria, Haemofilus influenza, and poliomyelitis have been evaluated. The children were vaccinated with the most commonly used pentavalent or hexavalent (DTPa-IPV-HIB, DTPa-HBV-IPV-HIB) vaccine and against pneumococci containing 10 or 13 serotypes (11, 4, 5, 6B, 7F, 9V, 14F, 19F, 23F); (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 23F). The analysis does not include obligatory vaccination against tuberculosis and hepatitis B. The material was analysed in two groups of gestational age: 23 0/7 – 28 6/7 – I group and in 29 0/7 – 33 6/7 weeks.

Results:
Of the 2149 neonates with gestational age ≤ 33 weeks only 388 (15.7%) were vaccinated against pneumococci before discharge home from the neonatal department. In newborns of maturity 23 0/7 – 28 6/7 gestational age these vaccinations were performed in 217 children, i.e. 51.05% of children with this maturity, which constitutes 55.92% of all vaccinated children against pneumococci. In the second group of 1724 children with the age of 29-33 weeks, the pneumococcal vaccination was given to 171 newborns, i.e. 44.08% of all pneumococcal vaccines, and 9.92% of children with this maturity born between 2015 and 2016. Vaccination with DTPa-HBV-IPV- HIB, or DTPa-IPV-HIB was performed in 340 (15.8%) newborns: 166 newborns in 2015 and 174 newborns in 2016.

Conclusions:
Despite international and Polish recommendations, the implementation of DTPa, IPVHib HBV, and PCV vaccination during hospitalisation of children in neonatal units does not cover all newborns ≤ 33 weeks of gestational age. Only slightly more than half of newborns in 23 0/7 – 28 6/7 gestational age whose hospitalisation in neonatal departments is on average 72 days, receive DTPa, IPVHib HBV, and PCV vaccination before discharge. In the Mazovia region there is a need to extend the procedure of vaccinations in neonatal departments for the safety and comfort of the child as well as the early identification of adverse events, which would allow proper intervention during hospitalisation.