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    The Ins and Outs of the Flu Vaccine

    By Rod Moser, PA, PhD

    Every year, about a hundred million influenza shots are given in the United States, along with hundreds of millions of other shots, including other vaccines, antibiotics and therapeutic drugs. The vast majority of injections are intramuscular (in the muscles), and the bulk of those given to larger children, adolescents and adults are administered in the deltoid muscle of the upper arm. Children and babies are typically given vaccines in the upper thigh since their deltoids are too small (and they tend to wiggle!).

    There has been a very active discussion taking place over the last year on WebMD’s Ear, Nose, and Throat Community involving several people who have experienced pain, weakness, paresthesia (tingling), numbness and other reactions in their arms or shoulders soon after receiving this year’s seasonal flu vaccine. I encourage you to read the comments, and offer your own insights.

    Although no vaccine, or injection for that matter, is devoid of side effects, the regular flu vaccine – the bulk of those injections – has an outstanding track record of being both safe and relatively effective. The flu vaccine is not 100% protective for a variety of reasons, nor is it free from side effects, but it is certainly safer than getting a full-blown case of true influenza.

    Typical reactions are usually mild and include brief pain at the injection site (Yes, shots hurt!). This pain usually resolves in a few hours at most. Some people experience soreness at the injection site, redness, or even swelling for a day or so. Rarely, the sterile needle will carry skin surface bacteria deep in the injection tract and a localized abscess can form. Some are “sterile abscesses,” often an accumulation or tiny pool of blood, and some are true bacterial abscesses. Since it can be difficult to determine this on examination, antibiotics are often given. Intramuscular needles can cut or nick blood vessels and nerves.

    Some people experience cold-like symptoms, such as fever, body aches, or sore throat after a flu vaccine. Many people incorrectly self-diagnose this as influenza, but inactivated (killed virus) vaccines biologically cannot cause the disease they are preventing. Even the live flu vaccines, like the nasally administered FluMist, can result in some minor cold-like responses.

    Severe reactions are extremely rare and usually occur quickly, within a few minutes to an hour. In 1976, a type of swine flu vaccine not used today was associated with a large number of cases of Guillian-Barre syndrome (GBS). My mother developed GBS from this strain of vaccine. Theoretically, GBS is still remotely possible from current flu vaccines – about 1-2 cases per million doses.

    Based on those reporting shoulder or arm pain on WebMD’s discussion board, there appears to be a general theme of improperly administered injections, resulting in neurological pain. While it is normal for people to blame the vaccine and not the shot itself for these reactions, the vaccine does not appear to be the culprit so far.

    Vaccines need to be administered in muscles because it offers a faster rate of absorption, and muscles can painlessly hold a larger volume of fluid. The deltoid muscle in the lateral upper arms is the preferred site, but the person administering an injection must be well-trained to avoid the radial nerve and artery, and to select a needle of proper size and gauge. So many different people are administering flu vaccines these days – from medical assistants to trainees and pharmacists – and many have only limited experience. Anxious patients can move. Needles may be inserted too deeply or at the wrong angle. It may be difficult for novices to know what sensitive structures are hiding beneath the skin, so proper techniques must be followed.

    This year, a safer and less-painful injection system has been approved for flu vaccine that uses a 90% shorter, ultra-fine needle that is only 0.06 inches in length, compared to the one-inch to 1.5-inch needles that are typically used for intramuscular injections. That’s for me!  This intradermal microinjection system deposits the vaccine in the dermal layers of the skin.  It would be highly unlikely for this tiny needle to damage peripheral nerves or hit major blood vessels.

    Because this new vaccine is given in the skin, local areas of redness are more readily seen, and people still experience some minor, transient soreness, swelling, or discomfort for a day or so following the injection. What they are unlikely to report is peripheral nerve pain or deep abscesses of any kind.

    Nerve damage as a direct result of an injection would likely be apparent immediately. The person would experience immediate numbness or tingling down the arm, perhaps following a peripheral nerve branch or the distribution of the radial nerve itself. Partial paralysis can occur if the damage is extensive. One can also experience various degrees of neuralgia (nerve pain) from compressive swelling deep in the injection site or from a hematoma (a pocket of accumulated blood). When tiny nerve branches are inadvertently needle-injured or compressed, it can take several weeks for the nerve to repair itself.

    When people experience an isolated improper injection or have uncomfortable side effects from a vaccine, a typical response would be to never have a flu shot again. While this seems like a simple solution, you may be ignoring the big picture. Influenza and its complications (like pneumonia) is the 8th leading cause of death. About 36,000 people or more per year die in the United States as a consequence of influenza. Worldwide, about 250,000 to 500,000 people die in a typical year with a typical flu strain. The most recent H1N1 pandemic resulted in only 16,000 deaths worldwide, but other historical pandemics have killed millions. These numbers are nothing to sneeze at.

    What should you do?

    1. Get your flu vaccine regardless. If you worry about needle-related complications, consider the new Fluzone intradermal vaccine or the nasally-administered flu vaccine (Flu Mist), assuming you meet specific age requirements.

    2. Familiarize yourself with the proper vaccine administration. Don’t hesitate to challenge the person giving you the shot if you feel it is being given incorrectly.

    3. During flu season (fall and winter months in the Northern hemisphere), people need to be extra careful about their person hygiene: wash hands thoroughly and often. Don’t freely cough or sneeze into the air, but rather in a tissue or, at the very least, into the crook of your arm (not the hands).  Wash your hands again and/or use an alcohol-based hand sanitizer.

    4. Avoid crowds if you can.  Keep your home and working environment well ventilated.

    5. Wear a surgical mask if you are ill or deal with potentially-ill people.  Sure, they look silly but influenza is not fun.

    6. Disinfect surfaces where flu viruses often accumulate, like door knobs, faucet handles, countertops, stair railings, etc. Flu viruses can remain on porous and non-porous services for hours or days.

    7. Stay home if you are sick, even if you can’t afford it. Otherwise, you will likely spread your respiratory illness or influenza to others. Avoid visiting nursing homes or hospitals if you feel you have the flu.

    8. Not all respiratory illnesses, like colds or bronchitis, are considered to be flu. Self diagnoses are often wrong. When it doubt, see your medical provider to be properly examined and diagnosed.

    9. Influenza, when diagnosed early in the first day or so, can be treated with antiviral medications to reduce the severity and duration of the illness.

    10. See that other family members, co-workers and close friends get the flu vaccination as well. Prevention is everyone’s responsibility.

    Have you had a bad reaction to a flu vaccine that made you rethink having one this year? Talk it out in the comments below or in our Ear, Nose, and Throat Community.


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