Vaccination: under 5 and immunocompromised

Medical Forum looks at the latest recommendations for vaccinating young Australian children.

ATAGI expanded the eligibility criteria for COVID vaccination on August 3rd to include Aussie children aged 6 months to <5 years who are either severely immunocompromised, have a disability, or have complex and/or multiple health conditions that increase their vulnerability to serious infection.

It follows the announcement by the TGA on July 19th that they had provisionally approved the new paediatric formulation of the Moderna COVID-19 vaccine (Spikevax) for use in children aged 6 months to <5 years.

Spikevax is now recommended for children aged 6 months to <5 years in specific health categories including the following or similar conditions:

  • Severe primary or secondary immunodeficiency, including those undergoing treatment for cancer, or on immunosuppressive treatments as listed in the ATAGI advice on 3rd primary doses of COVID vaccine in individuals who are severely immunocompromised
  • Bone marrow or stem cell transplant, or chimeric antigen T-cell (CAR-T) therapy
  • Complex congenital cardiac disease
  • Structural airway anomalies or chronic lung disease
  • Type 1 diabetes mellitus
  • Chronic neurological or neuromuscular conditions; or
  • A disability that requires frequent assistance with activities of daily living, such as severe cerebral palsy or down syndrome

ATAGI based this recommendation on first principles and the evidence of benefit in other age groups, with parents of eligible children aged 6 months to <5 years advised to act as soon as they can secure a vaccination clinic appointment.

The recommended dose of Moderna’s new formulation for this age group is 25 mcg, compared with 50 mcg dose for children aged 6 to 11 years, and 100 mcg dose for people aged 12 years and over.

The recommended interval between each dose is 8 weeks and data suggest that protection will predominantly be against severe illness rather than infection.

A clinical trial including some 5500 children aged 6 months to <5 years showed that the Moderna vaccine provided only modest protection against infection (vaccine efficacy 35-52%) with the Omicron variant after two doses (25 mcg per dose).

The Moderna vaccine has already been approved for this age group (and dosage) in the US, and for the period June 18th to July 20th, 2022, more than 544,000 children in this category had received at least one shot, with no serious safety issues reported to date by the CDC or FDA.

Second dose data can be expected from mid-August 2022.

Safety data from the trial reported the same adverse events commonly seen in other age groups after mRNA vaccination, although fever was more common in this age group compared to older children and adults – lasting approximately 1-2 days and occurring more often in children who had previously been infected.

Only one vaccine-related febrile convulsion was reported during the trial, which occurred in a 17-month-old child, two days after their first dose.

ATAGI is not recommending vaccination for all children aged 6 months to <5 years, as despite large numbers of infections occurring in children in Australia and internationally, studies reveal that very few in this age group have been severely impacted by the virus and are the least likely to require hospitalization.

This advice is under ongoing consideration based on data on the disease burden and epidemiology (including the emergence of new variants such as BA.4 and BA.5), vaccine supply, emerging data on vaccine use in this age group, and the availability of new vaccines.