The choice of needle for vaccination should be individual.
The correct choice of needle length and thickness is an important point in intramuscular administration of vaccines, according to the November issue of BMJ.
The correct choice of needle length and thickness is an important point in intramuscular administration of vaccines, according to the November issue of BMJ. As you know, most vaccines are given intramuscularly. Introducing vaccines into subcutaneous fat can slow the mobilization of the antigen. This is the reason for the low efficacy of vaccines against viral hepatitis B, rabies and influenza with their subcutaneous administration.
One explanation for this is that in adipose tissue, no immunocompetent cell is needed to trigger a full-fledged immune response. In addition, if the antigens are in the fatty tissue for several hours or days, they can be destroyed by tissue enzymes. The importance of these factors was confirmed by identifying the relationship between the expressed thickness of subcutaneous fat and a decrease in the production of antibodies for the vaccine administered.
The development of severe local reactions with intramuscular administration is quite rare. In a study of more than 10,000,000 people, they were only recorded in 0.4% of the cases. At the same time, with subcutaneous administration, abscesses and granulomas can develop. The occurrence of injection site adverse reactions in these cases is associated with lower blood supply to adipose tissue. Therefore, when administering vaccines containing aluminum salt as an adjuvant (vaccines against hepatitis A, B, diphtheria, tetanus, whooping cough), preference is given exclusively to intramuscular administration. With surface administration of these vaccines, the risk of developing local irritation reactions, formation of granulomas until the development of necrosis increases.
When studying the thickness of the subcutaneous fat layer above the deltoid muscle in 220 people, significant variability of this indicator was revealed. The thickness of subcutaneous fat in women was significantly higher than in men. The researchers suggested that a standard 16mm needle would not reach the muscle in 17% of men and almost 50% of women. For men weighing 59-118 kg and women 60-90 kg, a 25 mm needle may be necessary, and for women weighing more than 90 kg, 38 mm needles long should be used.
In addition to the size of the needle, the possible depth of the drug is determined by the technique of injection. In order for the needle to reach the muscle and for the vaccine not to penetrate under the skin, the choice of the length of the needle and the injection site must be made individually for each patient. The important parameters are also the quantity of vaccine administered, the age of the patient and the development of muscle tissue. The diameter of the needle is no less important. Large diameter needles distribute the vaccine over a large area, reducing the risk of developing local side effects.
Summarizing all these facts, the researchers propose to provide medical personnel with an assortment of needles, which will allow the selection of a needle of length and diameter individually for each patient.