Analysis of information sources in references of the Wikipedia article "Intramuscular injection" in English language version.
Aspiration before injection of vaccine is not recommended, as there are no large blood vessels at the recommended immunization sites and not aspirating before injection has been demonstrated to reduce pain.
Aspiration is not recommended before administering a vaccine.
The Danish Health and Medicines Authority's guidelines have long recommended this, and now the Statens Serum Institut is following suit.
However, it is not recommended to aspirate before intramuscular and subcutaneous vaccine injection provided that the vaccine is placed in the appropriate place … does not involve the risk of injecting intravenously because there are no large blood vessels in these sites. Aspiration can cause the vaccination to be more painful because it takes longer to give the vaccine
It has previously been recommended to aspirate before injection with Covid-19 vaccines in relation to investigation of a possible connection between injection with Vaxzevria® and the occurrence of rare and serious side effects. However, this is no longer a recommendation and Covid-19 vaccines can be injected without prior aspiration.
The Danish Health and Medicines Authority's guidelines have long recommended this, and now the Statens Serum Institut is following suit.