What is a Needle Stick Injury?

A Needle Stick Injury (NSI) occurs when a needle or other sharp object, such as a blade, which has a patient’s blood on it accidentally cuts someone else’s skin. The term ‘sharps injuries’ is often used interchangeably with ‘NSIs’. While the immediate impact of a NSI may seem trivial, its implications can be very serious. The main risk posed by NSIs from hypodermic sharps is exposure to blood borne viruses (BBVs). Hepatitis B, Hepatitis C, and HIV are the ones that get the most coverage, but many more diseases can be spread through NSIs as shown below

The USA’s International Safety Center’s annual EPINet reports provide information regarding the who, where and how of NSIs. Their 2022 report again indicates that disposable syringes, prefilled syringes & vacuum tube blood collection devices represent a very significant proportion of the reported NSIs.

Diseases transmitted by needle stick injury

Beside the major concerns of HIV, Hepatitis B and Hepatitis C, needle stick injuries have also transmitted many other diseases involving viruses, bacteria, fungi, and other microorganisms to health care workers, laboratory researchers, prison staff, waste disposal, and veterinarian staff.

The diseases include:

  • Parvovirus
  • Syphilis
  • Staphylococcus aureus
  • Rocky Montain spotted fever
  • Sporotrichosis
  • Diphtheria
  • West Nile Virus
  • Endocarditis
  • Blastomycosis

  • HTLV
  • Cutaneous Gonorrhoea
  • Mycobacteriosis
  • Cryptococcosis
  • Herpes
  • Toxoplasmosis
  • Cytomegalovirus
  • Epstein-Barr virus
  • Tuberculosis

  • Brucellosis
  • Ebola
  • Streptococcus Pygogenes
  • Hepatitis G
  • Tropical Spastic Paraparesis
  • Mycoplasma caviae
  • Hepatitis D
  • Malaria

Many of these diseases were transmitted in rare, isolated events. They still demonstrate, however, that needle stick injuries can have serious consequences. In addition to Blood-bourne diseases, there could also be consequences of an NSI from genetically modified drugs and some chemotherapy treatments.

Are NSIs still an issue?

Despite there being legislation in the USA, European Countries and many other countries around the world, NSIs remain a global problem.

Collection of data on NSIs varies greatly from country to country, and even where detailed and accurate accurate data is recorded, there is evidence that many instances are not reported.

2020 Meta-analysis re global prevalence of NSIs by Karen A Daley et al concluded that NSIs are many multiples more than WHO’s previous report of 2 million NSIs per year.

Annual EPINet and EXPO-S.T.O.P. surveys report rises in NSIs with more than 30% of these occurring with “safe” devices.


Current solutions

Companies are using different approaches to minimise the number of NSIs and protect the end user. The following is C-Major Medical’s analysis.
There are two broad approaches to reducing NSIs – either cover the needle after use (protective shields), or retract it so that it is no longer accessible.

Protective shields

Sheath (active)


Clip (active)

Syringe with retractable needle

Manual (active)


Automatic (passive)

Protective Shields

These are the simplest solutions and the lowest cost point of the range of safety syringes. However, their approach is so simplistic that on many occasions the safety mechanism does not work and most types do not meet the guidelines outlined below. Issues with this approach include:


  • These have limited use and tend to be targeted toward diabetics
  • Many of these require two hands to operate

  • With the needle partially covered, it is sometimes difficult to see and position the needle correctly, so they are often used only for intra-muscular injections


A plastic cover is provided with and pre-attached to the syringe or needle

  • It is a two-handed process to cover the needle after use. This is not ideal when the first priority of the clinician is to use one hand to cover the injected area on the patient with a plaster or gauze to stem any bleeding. More often than not, the clinician puts the syringe down first and then picks it up again later to cover the needle. This can leave unprotected, contaminated needles on a tray or other work surface, and can be a source of NSIs.
  • To cover the needle, you have to move your hand toward the contaminated end and swing the already attached cover over to attach it with a click. This is something that is not recommended as hands should always be behind the contaminated needle.

  • Some companies issue guidelines in an attempt to get over the two-handed approach. They recommend that the needle is lined up with the cover and sharply tapped onto a hard surface. This, however can produce an issue with splutter where the act of moving the syringe quickly can cause blood droplets to be ejected from the needle. The Royal College of Nursing’s guidance, to comply with the UK Health and Safety Sharp Instruments in Healthcare (2013), mandates that a safety device must not create other safety hazards or sources of blood exposure (such as splutter).
  • The cover is already attached to the syringe and can get in the way of the injection site, the cover often flops around as the needle is being inserted.

Syringe with retractable needle

The preferred mechanism, the needle is retracted back into the syringe, ensuring no possibility of a NSI post-retraction.

The two types of mechanism include:


  • An unpopular choice as it requires a two-handed process to enable the retraction.
  • The two-handed process is fiddly and could in itself cause an NSI or some other form of blood contamination to the user.

  • Research has shown that because of the need for the two-handed process, the safety feature is frequently not activated by the practitioner before disposal.


This type of product is currently the preferred format, and even though more expensive, the designs start to address some of the user requirements for a safety syringe. However, current designs do have significant shortcomings. These include:

  • Cannot be used for aspiration (withdrawing fluid from a patient including blood collection). All current designs retract the needle into the fluid chamber and thus cannot be used for blood collection or taking of other samples from the body, further limiting their use.
  • Retraction is triggered ‘automatically’ at the end of the injection stroke which could be while the needle is still in the patient. If the needle is in a vein, and either the patient or the practitioner moves during the retraction process, or the needle is bent during insertion, then there is a risk of injury to the patient. The current devices therefore, are not approved for intravenous procedures, again limiting their use.

  • Some require additional pressure on the plunger to engage the retraction mechanism and so can cause extra pain and risk of injury to patients.
  • One-handed trigger is possible, but with all current devices this occurs only at the end of the dispensing stroke. This means that retraction cannot occur if only a partial injection is made until the remaining injectant is disposed of in some other way.
  • Standard syringes are provided without needles, and clinicians select and fit the gauge/size of a standard needle to suit the application/patient. However, many existing auto-retracting devices incorporate needles as an integral fixed part, so many combinations of syringe size and needle gauge need to be stocked which increases cost. In addition, the inability to change needles after charging the syringe makes them incompatible with some current clinical practices.

C-Major Medical’s design concept was based upon user input. The key design criteria included:

  • Must be able to replace exactly what can be done with a standard simple syringe i.e. able to choose from a range of needles, able to change the needle after drawing up the injectant, and the ability to use the syringe to aspirate
  • Must be able to be made safe at any time without the clinician needing to use a second hand or change hand position

  • Must not create other hazards such as splutter, drips etc.
  • Must be intuitive to use to minimise extra training
  • Must not be significantly more expensive than current standard syringes​

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