However, Beasley said not all vaccines were rendered less effective if they were unintentionally deposited in the subcutaneous layer of fat above the muscle.
“The problem of the reduced effectiveness seems at this stage just to apply to influenza and hepatitis B and it has still not been determined the situation regarding the Covid vaccine,” Beasley said.
Ministry of Health statistics show more than a third of adults in Aotearoa were classified as obese, with the number of women rising from 31.9 percent in 2020 to 35.9 percent in the year ending 2021.
“One of the reasons this is a priority is that at the moment, the group in the population who are least likely to get the intramuscular vaccination is the population who have obesity and they are at greatest risk of the diseases that the vaccinations are designed to reduce,” Beasley said.
‘Large arms’ and other vaccine guidelines too vague
The research - published in prestigious medical journal The Lancet today - pointed to a global knowledge gap in the effective administration of vaccines to a significant and growing segment of the population.
“Currently, vague vaccination guideline terms such as ‘large arms’ can lead to a needle that is too short being used and vaccine being deposited in the subcutaneous tissue instead of the deltoid muscle.
“Our findings are really important globally as this issue will apply to all populations worldwide,” Beasley said.
Vaccines effective but side effects must be minimised
Immunisation Advisory Centre medical director Nikki Turner said large-scale vaccinations during the Covid-19 pandemic had brought the problem to the surface.
Turner said vaccinators would typically assess a person’s size through their BMI or weight, the size of their arm and consider how the vaccine would be delivered - either through bunched or straight skin.
“[It is] much harder [to assess those factors] when you are putting through large numbers of people. Also a lot of the Covid vaccines came with fixed needles, and the clinics needed access to the larger needles.
“Historically - in [GP] settings, in places where they knew the patients - it’s much easier to do and you have access to both needles. So it became much harder with mass vaccination clinics.”
Turner said the existing guidelines were clear, but they did require the vaccinator to make a professional judgment based on more factors than a single measurement.
“There has been discussion for many years about the potential to use a tape measure. You have to think about infection, you have to change the tape measure between people, it slows things down, it can become a barrier. So this is a pragmatic balance to try and get it right for everybody,” Turner said.
She said she felt the prime concern was not the potential for vaccines to be rendered ineffective but for the heightened potential for side effects when the jab did not go deep enough.
“If you put the vaccine too shallow in the arm, you have an increased risk of getting a local reaction so you might end up with a sorer arm or more of a red reaction, so that is what we’re trying to stop by using longer needles.
“I do not think people in New Zealand need to worry that their vaccines have been ineffective because they have not. It’s more about trying to minimise side effects,” Turner said.
Turner said she wanted to celebrate the job the country’s vaccinators had done getting through the recent years of mass vaccination clinics in the face of the Covid-19 pandemic.
- RNZ
