Is faulty injection technique behind rare clot disorder reported post Covid vaccination?
Studies suggest that faulty injection techniques may be the reason behind incidences of rare blood clot disorder being reported post Covid vaccination. (Photo: PTI file image for representation)  Recent global studies suggest that wrong injection techniques used to administer Covid-19 vaccines may be a reason behind incidences of blood clots being reported post vaccination. If the technique of administering the injection is wrong, the vaccine could get injected into the blood stream instead of reaching the muscle. This can lead to blood clots, health experts said. If the tip of the needle doesnt reach deep enough in the muscle or if it hits a blood vessel, the vaccine can be directly injected into the bloodstream. This is an extremely rare possibility. It can happen when the skin is pinched up by an inadequately trained health worker. Intra-muscular injections are supposed to be given without pinching up the skin, so that the needle tip reaches the muscle. When the skin is pinched up, the needle tip reaches only the subcutaneous tissue, said Dr Rajeev Jayadevan, a member of the Indian Medical Associations national Covid taskforce in Kochi, Kerala. (Photo: Twitter/Dr Jayadevan)  Dr Jayadevan explained further, When that happens, not only is the vaccine not absorbed properly, but rarely it can hit one of the blood vessels that travel through the subcutaneous layer which is located between skin and muscle. This layer contains a network of blood vessels.  One more problem is that people have stopped aspirating [pulling back the plunger of the syringe] to check if they hit a blood vessel while giving intra-muscular injections, he said. Unfortunately, many updated guidelines [from pre-pandemic days] suggest that aspirating for blood return in the syringe is no longer necessary. This leaves a small chance of missing an inadvertent intravenous injection. In the past, aspirating was standard practice to ensure that the tip of the needle had not hit a blood vessel, Dr Jayadevan said. ALSO READ: Scientists identify why Covid-19 patients develop life-threatening blood clots  He explained that if the needle tip enters a tiny blood vessel in this way, which happens only in the rarest of rare cases, the vaccine will directly enter the bloodstream and can potentially cause an acute reaction. Thus, there is a greater chance of the adenoviruses being injected directly into the bloodstream, he said. Sputnik V, Johnson & Johnson and the AstraZeneca vaccine are adenovirus vaccines. Across the globe, J&J and AstraZeneca vaccinations have resulted in some cases of blood clots. However, there is little data about adverse reactions post Sputnik V vaccination. Dr Jayadevan added, This was originally proposed by Professor Neils Hiby from Denmark in March this year.  MUNICH UNIVERSITY STUDY  Another study done on mice at the Munich University in Germany also suggests that this rare complication in adenovirus vaccines could be occurring as a result of the vaccine being injected into the blood stream. Vaccine candidates of different varieties such as AstraZeneca (adenovirus-vector), Pfizer (mRNA) and a placebo were used to check for outcomes following different routes of injection. The preprint of the study by Leo Nicolai and co-authors, posted on bioRxiv.org, highlighted accidental intravenous injection as a potential mechanism for post-vaccination thrombotic thrombocytopenic syndrome (TTS) also called vaccine-induced immune thrombotic thrombocytopenia (VITT). Our data provides first experimental support for the potential sequence of events that could lead to TTS in some patients: Thrombocytopenia might be a result of accidental intravenous adenovirus vaccine injection with ensuing platelet-adenovirus aggregation and activation with antibody formation. We recommend aspirating to check for blood in the syringe before injecting, the authors said. RISK OF VACCINE-INDUCED CLOTS IN MEN AND WOMEN  The risk of vaccine-induced clots is higher in women. The reasons for this are not fully known. Anatomically speaking, the needle is more likely to miss the deltoid muscle and hit the subcutaneous tissue in women. Dr Jayadevan said, Women have greater deltoid fat pad thickness - which means they have a thicker layer of fat separating the skin over the shoulder from the deltoid muscle underneath than men.  This means the needle has to penetrate deeper past the skin to hit muscle in women. The same length needle is used for both men and women. This means that the chance of missing the muscle with the needle is higher in women. There is published evidence that the chance of the tip of the needle being in the subcutaneous tissue is three times higher in women. Women may have other physiological risk factors for thrombosis too. It has been observed that the risk of blood clots following vaccination is lower in the case of the second dose as compared to the first. It is about ten times less common with the second dose. One of the likely reasons for this is prior exposure [first dose] to the virus and hence a milder immune response even if it enters the bloodstream inadvertently. In the case of the first dose, the body has never been exposed to the virus, explained Dr Jayadevan. CORRECT TECHNIQUE FOR INTRA-MUSCULAR INJECTION  1. Do not pinch skin up. Instead, gently stretch skin before plunging the needle at a 90 degree angle. 2. The needle tip needs to be in the muscle, not the subcutaneous tissue. 3. Aspirate gently before injecting. Make sure you havent hit a blood vessel. Denmarks Statens Serum Institut has already issued a special advisory regarding vaccination technique for all Covid-19 vaccines to prevent inadvertent injection into the bloodstream. The syringe has to be aspirated to check for blood before injecting the vaccine. ALSO READ: Decoded | What is vaccine passport and how you can get one