Buzz
In 2021, like many Americans, I volunteered at a mass vaccination site. Beneath a tent, healthcare professionals prepared syringes, which were then delivered by staff to cars where vaccinators administered the preloaded needles. Every person received the same vaccine, the same dosage, and the same needle size.
However, different bodies require different needle lengths, and needle size can influence the vaccine’s effectiveness in your body. If you're about to get this year’s COVID shot—or any vaccine—pay attention to this detail. If you are a female identifying and weigh over 200 pounds, or a male identifying and weigh over 265 pounds, you may need a longer needle—and you may need to advocate for it.
The needle must penetrate deep enough to reach your muscle
Most vaccines are administered into the muscle, and typically, vaccinators target the deltoid. This is the muscle in your upper arm, which sits underneath a layer of fat that everyone has. Ideally, the needle—usually one inch in length for both children and adults—pierces the fat and reaches the muscle.
However, since bodies vary, if there's more fat over the muscle, a one-inch needle may not be sufficient. Because of this, the CDC has long advised that body size should be considered when vaccinating, and recommends that adults use needles ranging from one inch to one-and-a-half inches.
While body weight plays a role in determining the appropriate needle length, it’s the body shape and size that are more important. Vaccinators are tasked with making this judgment by consulting with the patient before administering the vaccine. Also, the longer needle isn’t more painful—it’s not a thicker needle—so there shouldn’t be significant obstacles in following the CDC’s guidance.
How was I supposed to know about this?
It’s really not the patient’s responsibility to know this information—we generally expect that when we get a flu shot or any vaccine, the right equipment is used, and we don’t need to think twice about it. And there’s good reason for that expectation: Healthcare professionals receive education that includes this CDC recommendation.
During the pandemic, in response to urgent needs, the qualifications required for vaccinators were relaxed. However, even under these circumstances, most vaccination centers still mandated on-site training, which should have included the CDC's data on the subject.
The issue at hand is that weight bias in healthcare is both common and well-established. I interviewed six vaccinators who worked at large vaccination sites across the U.S. in 2021. Half of them were unaware of the CDC's guidelines, and only one mentioned adhering to them, using needles of various sizes. At my own mass vaccination site in Arizona early in 2021, we didn’t use different needle lengths. Most disturbingly, one vaccinator noted that, despite being aware of the guidelines, many healthcare professionals ignored them. 'I worked at both mass and smaller clinics and can tell you that the weight guidelines were largely dismissed by doctors and nurses. I would let the vaccinators handle it, not the patients. Most pharmacies only use one needle size.'
I contacted three pharmacies distributing the COVID vaccine: a CVS in midtown Manhattan, a Walgreens in Chicago, and a Rite Aid in Los Angeles. I asked the pharmacy managers if they were using different needle lengths based on patient weight. Only the Walgreens store confirmed they were. Both the Los Angeles and New York branches said they used one-inch needles for everyone. When I mentioned the needle-length recommendation, both seemed surprised by the information.
What happens if I don't receive a needle long enough to properly administer the vaccine?
We know that intramuscular vaccines must be delivered directly into the muscle, and a one-inch needle doesn't always reach that depth. What remains unclear is how this affects the vaccine's effectiveness, particularly for COVID. To assess this, we would typically use a titer test to measure antibodies or virus levels after vaccination. However, due to the lack of effective titer tools for COVID, such measurements are not possible. A 2010 study on adolescents with obesity who received the Hepatitis B vaccine, showed that using longer needles resulted in 80% higher titer levels post-vaccination.
The method of administering the vaccine is also crucial. Experienced vaccinators may be skilled enough to inject at an angle that still reaches the muscle. However, there’s no indication that vaccines administered with shorter needles than recommended are ineffective. It’s always better to receive the vaccine with a standard needle than to forgo it altogether.
How can I tell if I received a longer needle, and how can I request one?
Needle length isn’t listed in any medical records, so it's unlikely you'll know the exact length of the needle used in a previous vaccination. However, knowing this information could help you request a longer needle, if necessary, for future doses. I spoke with Dr. Shradha Chhabria, an MD specializing in obesity medicine and co-author of the 2022 paper mentioned earlier, to get her advice for patients who might need this adjustment.
Dr. Chhabria emphasized that there is scientific evidence supporting this request, which should help patients feel more confident when speaking up. 'This is a CDC standardized practice, that is irrefutable, and is part of any standardized vaccine training, according to CDC guidelines,' she explained. She encouraged patients to advocate for themselves. 'Anyone who is aware of these weight-based guidelines and understands that they could achieve better immunity if the right needle size is used should feel empowered to ask, 'Hey, my understanding is that the CDC recommends a 1.5-inch needle for my weight. Do you have any 1.5-inch needles available today?' Any vaccinator should recognize that this is the standard of care.'
If the vaccinator does not have the proper needle size, Dr. Chhabria suggested asking if they can obtain one. However, she also stressed that receiving the vaccine with a less-than-ideal needle is still better than not getting vaccinated at all.
