General Immunization Practices

Infection Control and Sterile Injection Technique

Infection resulting from administration of vaccines is unlikely if appropriate precautions are utilized. Hands should be washed with soap and water or cleansed with an alcohol-based waterless antiseptic hand rub before each patient contact to reduce the risk of bacterial contamination and transmission of microorganisms between vaccine recipients and healthcare personnel. In general, use of protective gloves is not necessary when administering vaccines unless the healthcare provider will have contact with potentially infectious body fluids or has open lesions on the hands. ^, However, in the setting of the COVID-19 Pandemic, gloves should be worn when administering oral or intranasal vaccines.

Failure to follow relevant infection control guidelines can result in transmission of bloodborne pathogens or bacterial infection and abscess formation. Contamination of an injection site can occur from bacteria on the skin at the site of injection. To prevent such contamination, skin at the injection site should be prepared with the application of isopropyl alcohol (70%) or another disinfecting agent and allowed to dry before injection. Transmission of pathogens also can occur if needles, syringes, vaccines, or other equipment used to administer vaccines becomes contaminated. To prevent such contamination, syringes and needles must be sterile. A separate needle and syringe should be used for each injection. Disposable needles and syringes should be discarded after a single use in a labeled, puncture-proof container to prevent inadvertent needle-stick injury or reuse. Because recapping and removing a used needle from a syringe can result in injury to the user, needles should not be recapped after use. The needle and syringe should be discarded as a single unit without removing the needle from the syringe. Single-use disposable needles and syringes should not be sterilized and reused.

If only reusable (i.e., nondisposable) needles and syringes are available, they must be thoroughly cleaned and sterilized after each injection to prevent transmission of bloodborne or other pathogens between patients. Reusable syringes are usually glass rather than plastic. Because of its inert characteristics, glass can be cleaned and sterilized more easily than plastic. Because hypodermic needles enter deep tissues, great care must be taken to ensure that all contaminants are removed from the needle and syringe. Liquid germicides alone are insufficient for needle sterilization because of the restricted access of the chemical agent to the lumen of the needle. Strict adherence to the recommended time and temperature for the sterilization procedure used must be observed.

Most vaccines have a similar appearance after they are drawn into a syringe. Cases in which the wrong vaccine was administered often are attributable to the practice of prefilling syringes or drawing doses of a vaccine into multiple syringes before their immediate need. The routine practice of prefilling syringes should be discouraged because of the potential for such administration errors. To prevent errors, vaccine doses should not be drawn into a syringe until immediately before administration. In certain circumstances in which a single vaccine type is used (e.g., in a mass influenza vaccination clinic), filling a small number (10 or fewer) of syringes before their immediate use may be considered. Care should be taken to ensure that the cold chain and sterility are maintained until the vaccine is administered. When the syringes are filled, the type of vaccine, lot number, and date of filling must be labeled accurately on each syringe, and the doses should be administered as soon as possible after filling, by the same person who filled the syringes. Manufacturer prefilled-syringes that are activated (i.e., syringe cap removed or needle attached) but unused should be discarded at the end of the clinic day. Likewise, unused vaccine drawn into syringes by the user (i.e., not by the manufacturer) should be discarded at the end of the clinic day.

Route of Administration

One or more routes of administration (e.g., intramuscular, subcutaneous, intradermal, intranasal, and oral) are recommended for each vaccine and are listed in the manufacturer’s product label and in published recommendations of immunization advisory committees ( Table 10.1 ). ^, These routes usually are determined during prelicensure vaccine studies and are based on vaccine composition and immunogenicity. Vaccines should be administered in sites where they elicit the desired immune response and where the likelihood of local tissue, neural, or vascular injury is minimal. To avoid unnecessary local and systemic adverse events and to ensure the appropriate immune response, people administering vaccines should not deviate from the recommended route of administration in the product label. A route of administration or anatomic site of injection different from that recommended can result in an inadequate immune response. For example, the immunogenicity of hepatitis B vaccine and rabies vaccine is substantially lower when the gluteal instead of the deltoid vaccination site is used. ^, The reduced immunogenicity presumably is a result of inadvertent injection into subcutaneous or deep fatty tissue rather than into muscle.

Deep intramuscular injection generally is recommended for adjuvant-containing vaccines because subcutaneous or intradermal administration can cause marked local irritation, induration, skin discoloration, inflammation, and granuloma formation. However, subcutaneous injection can lessen the risk of local neurovascular injury and is recommended for vaccines that are less reactogenic but immunogenic when administered by this route, such as live virus vaccines. Intradermal administration is preferred for live bacille Calmette-Guérin (BCG) vaccine.

Aspiration before injection of vaccines or toxoids (i.e., pulling back on the syringe plunger after needle insertion, before injection) is not necessary because there are no large blood vessels at the recommended injection sites. Also, the process of aspiration can be painful, especially for infants.

Subcutaneous Injections

Vaccines recommended for subcutaneous injection usually are administered into the thigh of infants younger than 12 months of age and into the upper, outer triceps area of persons 12 months of age or older. Subcutaneous injections also can be administered into the upper outer triceps area of an infant. A 5/8 inch, 23- to 25-gauge needle is recommended in most situations. ^, The needle is inserted into the tissues below the dermal layer of the skin (see Fig. 10.1 ). To avoid administering the vaccine into a muscle, the skin and subcutaneous tissue should be held gently between the thumb and fingers to raise these tissues from the muscle layer. The needle is inserted into the resulting skinfold at an approximately 45-degree angle.

Intramuscular Injections

Selection of the site of injection and needle size is based on the volume of vaccine to be administered, the thickness of the overlying subcutaneous tissue, the size of the muscle, and the desired depth below the muscle surface into which the material is to be injected.

The quadriceps muscle mass in the anterolateral thigh is most commonly used for intramuscular injection in infants younger than 12 months of age, whereas the deltoid muscle of the upper arm is the usual recommended site for older children and adults (see Fig. 10.2 ). One exception to using the deltoid muscle for injections in adults is administering COVID-19 vaccines in adult women who have had a mastectomy. Lymph node swelling is a known side effect of the COVID-19 vaccines. The COVID-19 vaccine can be administered in the deltoid muscle of the opposite arm or in the anterolateral thigh in such cases. After a child begins to walk, the upper arm is the preferred site. By this age, the child’s deltoid muscle is usually large enough to be used for intramuscular injection. Although the anterolateral thigh is also an acceptable site, intramuscular injection into the thighs of 18-month-old children has been reported to cause transient limping. ^, For infants and younger children, if more than two vaccines are injected in a single limb, the thigh is the preferred site because of the greater muscle mass; the injections should be sufficiently separated (i.e., ≥1 inch) so that any local reactions can be differentiated. ^,

Because of the potential risk of injury to the sciatic nerve, the gluteal region is not recommended for routine vaccination. ^, This recommendation is based primarily on reported cases of sciatic nerve injury resulting from injection of antimicrobial agents or antiserum into the gluteus. ^, No reports of direct nerve injury resulting from gluteal injection of current childhood vaccines have been published.

If injections are given in the gluteal site, care must be taken to avoid nerve injury. The central region of the buttocks should be avoided. The needle should be inserted into the upper, outer quadrant and directed anteriorly (i.e., not caudally or perpendicular to the skin surface). If the gluteal muscle is chosen, injection should be lateral and superior to a line between the posterior superior iliac spine and the greater trochanter or the ventrogluteal site (i.e., the center of the triangle bounded by the anterior superior iliac spine, the tubercle of the iliac crest, and the upper border of the greater trochanter of the femur). These areas are free of major neurovascular structures. Because of the large volume that must be injected and its large muscle mass, the gluteal site often is used for passive immunization with immunoglobulin preparations. ^,

A 22- to 25-gauge needle is appropriate for intramuscular administration of most vaccines. The ideal needle length may depend on the vaccination technique. One technique for intramuscular injections consists of gently bunching the muscle in the free hand while the needle is inserted perpendicular to the skin. A second technique consists of using the thumb and index finger to stretch the skin flat over the injection site while inserting the needle perpendicular to the skin and injecting the vaccine. ^,

The subcutaneous tissue and muscle layer thickness of the anterolateral thigh and deltoid region have been determined by ultrasonography. ^{, ,} On the basis of the resulting data, a 5/8 inch (16 mm) needle used according to the second technique described above is estimated to be adequate for intramuscular injection in the thigh of infants younger than 12 months and in the deltoid of toddlers 1–2 years of age. However, when using the “bunching” technique described above, a 7/8–1 inch (22–25 mm) needle would be necessary for adequate intramuscular penetration of the thigh of a 4-month-old infant and of the thigh and deltoid of toddlers and older children. ^{, , ,} For injection into the thigh of children 3 years through 10 years of age, the needle length must be 1- to 1.25-inches in length.

For adolescents (aged 11 years and older) and adults, the ideal needle length for intramuscular injection depends on the weight and sex of the vaccinee. For adolescents and adults, the deltoid muscle is preferred; however, the anterolateral thigh may be used, and if used the needle must be 1- to 1.5-inches in length. Poland and colleagues reported that women have a greater deltoid fat pad thickness by ultrasonography and a greater deltoid skinfold thickness than men of an equal body mass index. For adults 19 years and older weighing 130 lbs (60 kg) or less and weighing 130–152 lbs (60–70 kg), a 1 inch (25 mm) needle is recommended. For men weighing 152–260 lbs (70–118 kg), a 1–1.5 inch (25–38 mm) needle is recommended, and men weighing 260 lbs (118 kg) or more, a 1.5 inch (38 mm) needle is recommended. For women weighing less than 130 lbs (60 kg), a 5/8–1 inch (16–25 mm) needle is recommended. For women weighing 152–200 lbs (60–90 kg) a 1–1.5 inch (25–38 mm) needle is recommended, and a 1.5 inch (38 mm) needle is recommended for women who weigh more than 200 lbs (90 kg). ^,

Vaccinating Persons With Coagulation Disorders and Persons Receiving Anticoagulant Therapy

Persons with coagulation disorders such as hemophilia and persons receiving anticoagulant therapy (e.g., warfarin) can be at increased risk for bleeding after intramuscular injection. If possible, vaccination could be scheduled prior to the use of anticoagulant therapy so that the patients’ risk of bleeding is not increased by their therapeutic action.

A 23-gauge or smaller needle should be used for the vaccination, and firm pressure without rubbing should be applied to the site for at least 2 minutes following injection. Alternatively, vaccines recommended for intramuscular injection could be administered subcutaneously to persons with a bleeding disorder if the immune response and clinical reaction to these vaccines are expected to be comparable by either route of injection, such as meningococcal conjugate vaccine and hepatitis A vaccine. ^{, ,}

Percutaneous (Scarification) Injections

BCG and one of the smallpox vaccines (ACAM 2000®) are the only vaccines in the United States licensed for intradermal administration.

Smallpox (vaccinia) vaccine (ACAM 2000®) is administered by the percutaneous (scarification) route using multiple punctures with a unique bifurcated needle held perpendicular to the skin (see Chapter 55). A successful vaccination results in a pustular lesion (“Jennerian pustule”) at the vaccination site 6–8 days after primary vaccination. The skin reaction following revaccination may be less pronounced, with more rapid progression and healing, than that after primary vaccination.

Oral Administration

For vaccines given orally, the vaccine must be swallowed and retained. A dose of OPV should be repeated immediately if a patient spits out, does not swallow, or regurgitates a dose within 10 minutes after administration. However, readministration of rotavirus vaccine is not recommended if the dose is spat out or regurgitated. No data exist on the benefits or risks associated with readministering a dose of regurgitated rotavirus vaccine. The infant should receive the remaining recommended doses of rotavirus vaccine following the routine schedule (with a 4-week minimum interval between doses). ^,

Intranasal Route

Live attenuated influenza vaccine (LAIV4) is licensed for healthy nonpregnant persons 2 through 49 years of age and is the only vaccine administered by the intranasal route. The administration device is a nasal sprayer with a dose-divider clip that allows introduction of one 0.1 mL spray into each of the nares. The tip should be inserted slightly into each one of the nares before administration. Even if the person coughs or sneezes immediately after administration or the dose is expelled any other way, the vaccine dose does not need to be repeated. Introduction of low levels of vaccine viruses into the environment likely is unavoidable when administering LAIV4; however, no cases have been reported of illness or attenuated vaccine virus infections among inadvertently exposed healthcare providers or immunocompromised patients. The risk for acquiring vaccine viruses from the environment is unknown but is likely low; in addition, vaccine viruses are cold-adapted and attenuated and unlikely to cause symptomatic influenza. Severely immunosuppressed persons should not administer LAIV4. However, other persons at higher risk for influenza complications can administer LAIV4. These include persons with underlying medical conditions placing them at higher risk or who are likely to be at risk, including pregnant women, persons with asthma, and persons 50 years or older.

Needle-Shielding/Needle-Free Devices

Bloodborne diseases (e.g., hepatitides B and C and HIV) are occupational hazards for healthcare providers. In November 2000, to reduce the incidence of needlestick injuries among healthcare providers and the consequent risk for bloodborne diseases acquired from patients, the Needlestick Safety and Prevention Act was signed into law in the United States. The act directed the U.S. Occupational Safety and Health Administration (OSHA) to strengthen its existing bloodborne pathogen standards. Those standards were revised and became effective in April 2001. These federal regulations require the use of engineering and work practice controls to eliminate or minimize employee exposure to bloodborne pathogens. “Engineering controls” mean controls (e.g., sharps disposal containers; self-sheathing needles; and safer medical devices, such as sharps with engineered sharps injury protections and needleless systems) that isolate or remove the bloodborne pathogens hazard from the workplace. Work practice controls mean procedures followed by employers and workers to control hazards in the workplace (e.g., good housekeeping practices; closed transfers/containers/processes; and hygiene procedures).

Additional information regarding implementation and enforcement of these regulations is available at the OSHA website.

Jet Injectors

Jet injectors (JIs) are needle-free devices that drive liquid medication through a nozzle orifice, creating a narrow stream under high pressure that penetrates skin to deliver a drug or vaccine into intradermal, subcutaneous, or intramuscular tissues. JIs have the potential to reduce the frequency of needlestick injuries to healthcare providers and to overcome the improper reuse and other drawbacks of needles and syringes in economically developing countries. JIs have been reported safe and effective in administering different live and inactivated vaccines for viral and bacterial diseases. The immune responses generated are equivalent to, and occasionally greater than, immune responses induced by needle injection. However, local reactions or injury (e.g., redness, induration, pain, blood, ecchymosis, and transient neuropathy at the injection site) can be more frequent when vaccines are delivered by JIs compared with needle injection.

In the 1990s, a new generation of JIs was introduced with disposable cartridges serving as dose chambers and nozzle. With the provision of a new sterile cartridge for each patient and correct use, these devices avoid safety concerns for multiple-use-nozzle devices. These devices should be used in accordance with their labeling for intradermal, subcutaneous, or intramuscular administration. One brand of inactivated influenza vaccine has been approved by the U.S. Food and Drug Administration for use with a JI device. ^,