Some people may benefit from longer vaccination needles, according to the Centers for Disease Control and Prevention (CDC).

Recent discussions on social media have shed light on the fact that some people with bigger bodies should be given certain intramuscular vaccines—like the COVID-19 vaccine—with longer needles.

But while this recommendation comes from health authorities like the CDC, experts worry it may not always get put into practice.

“I don’t know if we’re doing enough quality assurance to make sure we’re following these recommendations,” Matthew Laurens, MD, MPH, who conducts studies at the University of Maryland’s Center for Vaccine Development, told Health.

It’s plausible that some healthcare workers who administer vaccines could sometimes use the wrong needle length for people with bigger bodies, Amesh Adalja, MD, a biosecurity and emerging infectious diseases expert at Johns Hopkins Bloomberg School of Public Health, told Health.

“It may be [the case] that people become lax about that when they’re injecting,” Adalja said. “If you’re obese or overweight, it would be useful to ask the injector if that’s the correct needle length for your body size.”

Here’s who may benefit from a longer needle length for vaccinations.

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Intramuscular vaccines, like the COVID vaccine, are injected into one of the deltoid muscles, which crowns your shoulders.

This muscle is below a layer of skin, fat, and connective tissue that can vary from person to person, Adalja explained.

This is why different needle lengths are recommended for different body sizes.

“With intramuscular [vaccines], you have to advance the needle beyond the subcutaneous layer,” Laurens said.

In addition to ensuring the vaccine is administered effectively, using the right needle length can also lessen the chances of adverse effects like swelling or redness at the vaccination site, Laurens said.

The CDC recommends that clinicians use the following scale to determine which needle length to use on adults 19 and older: 

  • A needle that is five-eighths of an inch on men and women who weigh less than 130 pounds.
  • A needle that is one inch on men and women who weigh 130 to 152 pounds.
  • A needle that falls between one and one-and-a-half inches on women who weigh 152 to 200 pounds and men who weigh 152 to 260 pounds.
  • A needle that is one-and-a-half inches on women who weigh more than 200 pounds and men who weigh more than 260 pounds.

The CDC notes that all intramuscular injections should be given with needles that are long enough to hit a person’s muscle mass but not so long that they reach underlying nerves, bone, or blood vessels.

Since not all vaccines are intramuscular, there are requirement differences in needle length depending on the person receiving the vaccine.

Some people online have spoken out about going to a pharmacy to get a vaccine and not being offered the correct needle length for their body size.

Since the ideal lengths differ depending on body weight, it’s a good idea to check with your provider to make sure they’re using the right one when you go get your COVID vaccine this fall, Laurens said.

That said, it may be difficult to tell which needle length your provider is planning to use after they’ve prepared the vaccine—spotting a half-inch difference isn’t easy—so it’s worth checking and having a conversation ahead of time to make sure they’re planning to use the correct size for your body.

If you recently received a COVID vaccine, and you suspect your provider didn’t use the right needle length for you, that doesn’t mean that your vaccine won’t still provide protection—though it might not provide as much protection as it could have, Adalja said.

Vaccines given with the wrong needle length would likely “still have some protection,” he explained. “Even if some of [the vaccine] doesn’t reach your muscle, there’s likely still going to be an immune response to it.”

The way a vaccine is given, as well as the needle length used, can affect its efficacy, he added.

For instance, it could be the case that, while your provider didn’t use the preferred needle length, they pushed harder to make sure the vaccine was injected into the area it was supposed to reach, the deltoid muscle.

“It may just be that it might not have been delivered as well [as it could have been], and it might not have worked as optimally—but it’s not an all-or-none type phenomenon,” Adalja said.

In an ideal world, healthcare workers would follow all CDC recommendations, including using the recommended needle length for all patients who show up to get the COVID vaccine, Laurens said.

“I think it’s worth looking at how we’re implementing this,” he explained. “I think it does deserve attention.”

For this reason, double-checking with your provider before you get the COVID vaccine to make sure they’re using the correct length can not only make sure you get as much protection as possible but also, potentially, help future patients as well.

“I think it’s great to be as informed as possible about the vaccine, including the length of the needle,” Laurens said. “The more informed we are, and the more we hold each other accountable, the better outcomes we have.”


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