In this week’s blog Dr Helen Sisson, @hsisson1 Lecturer in Public Health revisits the importance of timely vaccination in premature infants for World Prematurity Day on 17th November 2023.

Vaccination has been hailed as a key strategy in the prevention of infection in children, and the UK has well-established programmes in place (1). The latest Parental Attitudes Survey (2) indicates that over 90% of parents think that vaccines are safe and effective, yet the uptake of vaccines across the childhood programme has declined in recent years (3). This emphasizes the need to monitor uptake and identify strategies promoting uptake which target under vaccinated groups. Preterm infants are a population at increased risk of infection (4) making vaccinating them in a timely manner extremely important.

Even infants born prematurely have a functioning immune system (5); for both preterm and full-term infants, the immune system matures with age (6). However, preterm infants may face additional infection risks due to the need to undergo invasive clinical procedures (7). Antenatally, maternal antibody begins to cross the placenta from about 13 weeks, and this provides some important passive protection for infants in the early weeks of life. Yet, the vast majority of antibody transfer happens after 32 weeks gestation – this means that infants born before this point will not have benefitted from this significant protection (8) increasing their vulnerability to infection.

The primary vaccination series in the UK begins at 8-weeks of age, and vaccines are offered to all infants, regardless of gestational age. Whilst preterm infants are known to tolerate vaccination and make a response which is considered to infer protection (9) it is recommended that extremely preterm infants undergo a period of monitoring post-vaccination due to an increased risk of apnoeic events (10). It is acknowledged that some preterm infants may have genuine reasons for vaccines to be deferred, but prematurity should never exclusively be a reason to delay or withhold vaccination (10).

Despite global recommendations that preterm infants should receive their vaccines at the same time as their full-term counterparts, empirical evidence undertaken outside of the UK suggests that they face unwarranted delays, with infants of the lowest gestational ages facing the longest delays (11, 12). Therefore, understanding uptake in preterm infants in the UK specifically is important, and the availability of large digital datasets means that studying this at a population level is now possible. My recent study took a population-based approach aimed at investigating the notion of a delay in preterm infants receiving their primary vaccines was undertaken; it also sought to establish any additional infant and parental characteristics associated with timeliness of vaccination. This study has been submitted for publication (13) and it is envisaged that the findings will support practitioners and policy makers alike in their efforts to promote timely vaccination in preterm infants.

This year, World Prematurity Day falls on 17^th November; a day which acknowledges the challenges faced by premature infants and their families (14). This presents an opportunity to raise awareness among parents and health professionals about the importance of timely vaccination in preterm infants.

Public Health England (2019) have produced immunisation information aimed specifically at parents of premature infants (link below) – this may serve as a prompt for parents to voice any concerns and an opportunity to start a discussion about the importance of vaccination for preterm infants. https://www.gov.uk/government/publications/a-quick-guide-to-childhood-immunisation-for-the-parents-of-premature-babies

Further information for health professionals is available via Chapter 7 of Immunisation against infectious disease (The Green Book): https://www.gov.uk/government/publications/immunisation-of-individuals-with-underlying-medical-conditions-the-green-book-chapter-7  This considers immunising individuals with underlying health conditions, and premature infants are included given their heightened vulnerability.

References

1. UK Health Security Agency (2023) Complete routine immunisation schedule. Available online: https://www.gov.uk/government/publications/the-complete-routine-immunisation-schedule [Accessed 06/10/2023].
2. UK Health Security Agency (2023) Childhood vaccines: parental attitudes survey 2022. Available online: https://www.gov.uk/government/publications/childhood-vaccines-parental-attitudes-survey-2022 [Accessed 06/10/2023].
3. NHS Digital (2023) Childhood Vaccination Coverage Statistics. Available online: https://digital.nhs.uk/data-and-information/publications/statistical/nhs-immunisation-statistics [Accessed 06/10/2023].
4. Collins, A, Weitkamp, J-H, Wynn, J (2018) Why are preterm newborns at increased risk of infection? Archives of Disease in Childhood Fetal Neonatal Edition. 103(4); F391-F394.
5. Vaccine Knowledge (2018) Vaccine and premature babies. Available online: https://vaccineknowledge.ox.ac.uk/premature-babies [Accessed 06/10/2023].
6. Crofts, K, Alexander-Miller, M (2020) Challenges for the Newborn Immune Response to Respiratory Virus Infection and Vaccination. Vaccines. 8(4); 558.
7. Lissauer, T, Fanaroff, A, Miall, L, Fanaroff, J (2020) Neonatology at a Glance, 4^th edition. Chichester: John Wiley and Sons Ltd.
8. Ciobanu, A, Dumitru, A, Gica, N, Botexatu, R, Peltecu, G, Panaitescu, A (2020) Benefits and Risks of IgG Transplacental Transfer. Diagnostics. 10(8); 583.
9. Sadeck, L, Kfouri, R (2023) An update on vaccination in preterm infants. Journal de Pediatria. 99(Supp 1); S81-S86.
10. UK Health Security Agency (2022) The UK immunisation schedule: the green book, chapter 11. Available online: https://www.gov.uk/government/publications/immunisation-schedule-the-green-book-chapter-11 [Accessed 06/10/2023].
11. Bary-Weisberg, D, Stein-Zamir, C (2021) Vaccination timeliness and completeness among preterm and low birthweight infants: a national; cohort study. Human Vaccines and Immunotherapeutics. 17(6); 1666-1674.
12. Rouers, E, Berbers, G, van Dongen J, Sanders, E, Bruijning-Verhagen P (2019) Timeliness of immunisations in preterm infants in the Netherlands. Vaccine. 37; 5862-5867.
13. Sisson, H (2023) Vaccinating preterm infants: a regional study of timeliness. Primary Health Care. Manuscript submitted for publication.
14. Bliss (2023) What is World Prematurity Day? Available online: https://www.bliss.org.uk/support-bliss/world-prematurity-day/what-is-world-prematurity-day#:~:text=World%20Prematurity%20Day%20(17th%20November,it%20can%20have%20on%20families. [Accessed 06/10/2023].