Photo by Ivan Diaz on Unsplash
Photo by Ivan Diaz on Unsplash

COVID-19 vaccine may work even if it doesn't reach the muscle

Embargoed until: Publicly released:
Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Observational study: A study in which the subject is observed to see if there is a relationship between two or more things (eg: the consumption of diet drinks and obesity). Observational studies cannot prove that one thing causes another, only that they are linked.

People: This is a study based on research using people.

New research shows standard Covid-19 vaccination needles are too short to reach the muscle tissue in some people with larger arms. However the study also found those people had similar antibody levels to those who had been injected with an appropriately sized needle – meaning the jab may not need to reach the muscle for the vaccine to be effective against the virus. The authors say that because obesity is a major risk factor for COVID-19 illness and death, it's especially important that those with obesity are properly protected.

Journal/conference: Vaccine

Link to research (DOI): 10.1016/j.vaccine.2022.06.070

Organisation/s: University of Auckland, University of Otago, Medical Research Institute of New Zealand, Auckland District Health Board, Counties Manukau District Health Board, Capital and Coast District Health Board

Funder: This study was partly funded by the New Zealand Ministry of Health.

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Dr Thomas Hills, Clinical Immunologist, Auckland City Hospital

The standard length needle might not reach the muscle of some people, such as those with big arms.

We wanted to assess if the immune response to the COVID vaccine was lower in the small number of people who have a skin to muscle distance, measured by ultrasound, that was longer than the needle used for their vaccination.

The antibody response was the same in people who were vaccinated with needles that were probably too short to reach the muscle and those vaccinated with appropriate length needles.

This is reassuring and means that injection into the muscle may not be needed for the vaccine to produce a good immune response.

Last updated: 01 Jul 2022 11:27am
Declared conflicts of interest:
Thomas Hills is a lead author on this research. The study was led by a team from the University of Auckland, in collaboration with the Medical Research Institute of New Zealand, and was undertaken with the support of the Ministry of Health. It was performed at a COVID-19 Vaccination Centre in Auckland.

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