Factors influencing needle-length selection for adult deltoid intramuscular vaccination: an online survey of New Zealand vaccinators' practice.

Abstract

Introduction: Data from Aotearoa-New Zealand's 2021 COVID-19 mass vaccination programme revealed underutilisation of longer 38 mm needles, which are recommended for big-bodied people. This raises health equity concerns because correct needle length is necessary to achieve intramuscular vaccine delivery.

Aim: This study aimed to explore vaccinators' awareness and implementation of needle-length guidance, and to identify barriers and enablers to use of long needles for big-bodied people in New Zealand.

Method: Between August and October 2025, an anonymous online survey was distributed to vaccinators in New Zealand through professional organisations with links to vaccinator health professionals. Data collection included demographics, education received on needle-length guidance, barriers and enablers to use of 38 mm long needles, and opportunities to support future practice. Data were summarised using descriptive statistics, and comments summarised using a qualitative descriptive approach.

Results: Of 196 respondents, 70% were aware of needle-length guidance and 48.5% recalled receipt of specific information or education about using longer needles. In total, 60% had ever used a 38 mm needle, but only 26% had used a longer needle for at least half of those they thought eligible in the past 12 months. Key barriers to long needle use included supply of vaccines with shorter needle lengths attached, information gaps and uncertainty in determining eligibility for a 38 mm long needle. A total of 62% saw a need for strategies to strengthen their implementation of needle-length guidance.

Discussion: A range of strategies need to be implemented across multiple levels (from vaccinators through to policy makers) to overcome these barriers and to support safe and effective vaccine delivery to big-bodied people.