Preterm and low birthweight infants

Background

Preterm describes infants born before 37 weeks of pregnancy is completed; this is also known as prematurity.

Being very preterm (28 to less than 32 weeks’ gestation), being extremely preterm (less than 28 weeks’ gestation) and/or being born with low birthweight (under 2.5 kg, or 2500 g) are all factors associated with poorer health outcomes, including being at increased risk of infection and complications from infections.

The increased risk of infections and complications may be due to a variety of factors, including the need for prolonged hospitalisation and having chronic conditions associated with low birthweight or prematurity.

Recommendations

In addition to the routine vaccines on the National Immunisation Program (NIP), extremely or very preterm and low birthweight infants are recommended additional doses and vaccines to ensure optimum protection. The presence of specific medical conditions may also warrant administration of other vaccines.

Timing of administration

Administration of vaccines to preterm infants should be timed according to chronological age (actual age counted from birth) as opposed to a corrected age (the age an infant would be if they were born on their due date). Timeliness is important to minimise the window preterm infants are not protected from vaccine-preventable diseases. Depending on gestation at delivery, preterm infants may not have had the opportunity to gain the passive protection of pertussis, respiratory syncytial virus (RSV) and influenza from their mothers in utero.

Rotavirus vaccination must be administered within a strict timeframe, with the first dose required before turning 15 weeks old (chronological or actual age) and the second dose before 25 weeks of age. There is no catch-up if an infant has missed these cut-off dates. 

Pneumococcal

Infants born at less than 28 weeks’ gestation are at greater risk of invasive pneumococcal disease.

It is recommended that an additional dose of Prevenar 13 (PCV13) be administered at 6 months of age (total of 4 doses, given at 6 weeks, 4 months, 6 months and 12 months of age). They should also receive a dose of Pneumovax 23 (PPV23) at 4 years of age.

Where there is an ongoing risk for pneumococcal disease (Aboriginal and Torres Strait Islander children or those with specified medical conditions), a second (and final) dose of Pneumovax 23 should be administered 5 years after the first dose.

Hepatitis B

Infants born weighing less than 2000 g and infants born at less than 32 weeks’ gestation (regardless of birthweight) require an additional dose of vaccine to mount the same response as infants born of average weight and born at term receiving a standard course.

This additional hepatitis B dose should be given at 12 months of age (total 5 doses, birth, 6 weeks, 4 months, 6 months and 12 months). The birth dose of hepatitis B can be given up to Day 7 of life (prior to turning 8 days old). There is no catch-up if it is not given by this time.

Pre- and post-vaccination serology is not routinely required or recommended.

Influenza

Infants born preterm, have a high risk of severe disease and complications from influenza infection.

Annual vaccination is recommended from 6 months of age. Two doses, a minimum of 4 weeks apart, should be given anyone under 9 years of age in the first year of receiving the influenza vaccine, with a single annual dose recommended in subsequent years.

RSV

Infants born at less than 32 weeks’ gestation are at increased risk of severe disease and complications if infected with RSV. 

Regardless of whether their mother was vaccinated against RSV during pregnancy, these infants are recommended to receive RSV immunoglobulin (Nirsevimab). Protection gained from Nirsevimab lasts around 5 months and administration should therefore be timed to optimise protection over the RSV season (April to September). 

Household contacts

Family members and other household contacts of preterm infants should ensure they are up to date with all recommended vaccines, particularly influenza, pertussis and COVID-19. 

Side effects

In addition to the small list of common and expected side effects, apnoea (pause in breathing) has been reported following administration of vaccines to preterm infants.  Most apnoeic events self-resolve and are not associated with long-term complications. However, there is a small chance of recurrence following future vaccines.

Apnoeas and any unexpected side effects should be reported to and followed up by the adverse event reporting service in your jurisdiction.

Access

Additional vaccines recommended to preterm and low birthweight infants are funded via the NIP and can be accessed through GPs, council immunisation services, Aboriginal Health Services and specialist immunisation clinics.

Different Australian jurisdictions have different approaches to RSV immunoglobulin programs.

Resources

• MVEC: Influenza  
• MVEC: Rotavirus 
• MVEC: Respiratory syncytial virus (RSV)
• MVEC: Maternal vaccination during pregnancy 
• Ordering Preterm infant stickers for child healthcare books 
• The Royal Women’s Hospital: Fact sheet on immunisation for babies in intensive and special care
• MVEC: Vaccine administration
• Clifford V, Crawford NW, Royle J et al. Recurrent apneoea post immunisation: Informing re-immunisation policy. Vaccine. 2011;29(34):5681-5687. doi:10.1016/j.vaccine.2011.06.005