The CDC says it is "not necessary". I asked my local pharmacy and they will not do it even upon request and I am OK with that. But I have a question.

By accident I happened to see a video on youtube from the U.K. by a one "Dr. John Campbell" on the many evils of not using aspiration. I did not know what it was before yesterday nor never even heard of it.:). Never heard of the channel, it was by accident. He implied or should I say insinuated the risk of myocarditis cases in covid vaccine may be higher or caused by not using aspiration.

So is it basically a luck of the draw in the U.S. assuming you don't hit a vein or are the facts somewhat distorted by this video. I wondered that too. The chance may be so small it may not be an issue.

Any ideas appreciated.

  • 2
    The medical community doesn't make decisions based on what random people post on YouTube. Oct 25 at 16:55
  • 2
    Pretty related medicalsciences.stackexchange.com/questions/26146/…
    – Fizz
    Oct 25 at 18:11
  • 1
    @Sedumjoy This is why it's a good idea to wait a day or two before accepting an answer.
    – Carey Gregory
    Oct 25 at 19:10
  • 2
    If these results are confirmed in humans, it might lead the CDC to reverse course and recommend aspiration, at least with adenovirus vaccines.
    – Carey Gregory
    Oct 25 at 20:48
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    @BryanKrause I’ll say that while that statement is true in general, Dr Campbell is a highly reliable source, using widely accepted science and the latest information available. He’s especially good at highlighting variants which have potential for changing the shape of the pandemic.
    – Tim
    Oct 26 at 9:19

Aspiration has the negative side effect of causing more trauma since the needle will be wiggling around in the body while the syringe plunger is pulled back. Modern medical consensus is that the additional trauma of aspiration isn't worth the benefit, particularly when doing deltoid (shoulder) injections. The deltoid injection site is relatively free of veins and nerves. Depending on the needle gauge, the needle tip could actually be in some small veins/capillaries and aspiration would give a false negative (i.e. pulling back the plunger just creates a vacuum in the syringe). Because of its dubious efficacy and the risks of increased scar tissue and subcutaneous leaks, aspiration has fallen out of favor.

  • 3
    Hi Becky, welcome to Medical Sciences Stack Exchange. This answer would be substantially improved by references to back up the assertions. Oct 25 at 17:46
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    Actually, references are required. Answers without supporting references are subject to deletion. Please edit the post and add at least one link to a supporting reference. Providing a brief quote from the link would also be appreciated in case the link ever goes bad.
    – Carey Gregory
    Oct 25 at 19:13

The CDC gives this as the reason why not:

Aspiration before injection of vaccines or toxoids (i.e., pulling back on the syringe plunger after needle insertion but before injection) is not necessary because no large blood vessels are present at the recommended injection sites, and a process that includes aspiration might be more painful for infants.

[citing] Groswasser J, Kahn A, Bouche B, Hanquinet S, Perlmuter N, Hessel L. Needle length and injection technique for efficient intramuscular vaccine delivery in infants and children evaluated through an ultrasonographic determination of subcutaneous and muscle layer thickness. Pediatrics. 1997;100(3 Pt 1):400-403. DOI: 10.1542/peds.100.3.400

Other health authorities such as this one from Ontario seem to agree, citing more recent reviews:

Aspiration is not recommended. There are no large blood vessels near the intended deltoid injection site. Aspiration may increase the time it takes to immunize and be more painful for the client.


Regarding myocarditis a recent animal (mouse) study indeed found increased incidence of markers with deliberate i.v. injection. However, to demonstrate that the proposed solution, i.e. aspiration, would reduce the incidence in a real clinical setting would require pretty large human studies, as the incidence of this side effect seems to be around 1 in 15,000 or so. There are also some factors that are fairly hard to square with this (injection technique) hypothesis, namely that incidence seems to be higher after the 2nd dose:

while the Clinical Infectious Diseases study “supports the possibility that inadvertent injection into a blood vessel could result in undesirable reactions […] the majority of myocarditis cases are occurring in young males after the second dose, something that this hypothesis does not explain.”

  • the link to "namely" was a nice find. Thank you. I am glad I had so many people not reject my question and give it a sincere answer. Thk you.
    – Sedumjoy
    Oct 26 at 14:38

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