‍Immunisation stress-related response (ISRR) refers to the range of symptoms which may appear in response to the process of being vaccinated rather due to the vaccine itself.

Contributing factors

A combination of factors can influence how an individual responds, including physiological factors (age, sex, weight), psychological factors (coping strengths and vulnerabilities), and prior knowledge or preparedness. These can be further influenced by particular social contexts (eg, trust in health care, response by others, social media).

ISRRs may occur before, during and after a vaccine is administered. They arise from anxiety about the immunisation and can include vasovagal reactions (fainting, nausea), hyperventilation and stress-related neurologic reactions or disorders. Differentiating such reactions from anaphylaxis or other severe adverse events is important both for the individual and to maintain confidence in vaccination programmes. Mismanagement of individuals may lead to inappropriate use of

medications and unnecessary investigations. Mass reporting of ISRR during school-based vaccination programmes has at times led to marked reductions in vaccine uptake.

It is well recognised that psychological factors, like anxiety, can affect physiologic functioning such as pulse and blood pressure.

• Dizziness and fainting (vasovagal reaction) can result from the slowing of the heart and dilatation of blood vessels leading to reduced blood flow to the brain - the fight or flight response in overdrive.

• Rapid breathing or hyperventilation leads to shortness of breath, chest pain and tingling in the fingers, light-headedness, dizziness and headache.

Prevention and management

Prevention of ISRR begins before the vaccination, by trying to reduce anxiety and fear as much as possible. It is important to ensure environmental factors such as overheated, crowed waiting rooms, lack of privacy and negative social media communications are minimised. It is important for vaccinators to be friendly, confident and relaxed, able to communicate clearly and be receptive to each individual’s concerns and needs. A muscle tension exercise can help those with a history of a vasovagal reaction.

Recognition of ISRR at the vaccination site and differentiation from anaphylaxis is important. An incorrect diagnosis of anaphylaxis may lead to inappropriate management with adrenaline and may prevent a person from receiving further vaccinations. When an ISRR is identified, it is important to explain that they are not related to the vaccine itself or an error, that they are recognised responses and will resolve spontaneously. When a stress response is appropriately identified Efforts can be made the next time a patient is vaccinated to make the patient feel more comfortable and reassured to reduce the risk of recurrence.

Neurological stress-related symptoms

• Neurological symptom reactions can also occur and may start days after the injection. These may include weakness or paralysis, abnormal movements or postures, walking or speech difficulties and non-epileptic seizures (involuntary but not associated with the typical brain discharges that occur with epilepsy). These neurological symptoms can cause distress and significantly impact on daily activities. They are seen most often in females and in the 15-to- 24-year age group.

Neurological stress-related symptoms need to be differentiated from other neurological conditions. Management requires a multidisciplinary approach to reduce long term impact. Physiotherapy, cognitive behavioural therapy or medications may be required. It is important to establish a balance between investigation, reassurance and empathy, to create an atmosphere in which anxiety can dissipate, and fears subside. In this way, those affected can return to health with their dignity and self-respect unaffected.

Other examples of neurological stress-related reactions, that most commonly occur in stress events, other than vaccination, include:

• Complex regional pain syndrome (CRPS) - characterised by continuing pain which is considered to be out of proportion to the severity of the initial injury or event

• Postural orthostatic tachycardia (POTS)- characterised by an abnormally large increase in heart rate with changing from a lying down to a standing up position and often accompanied by symptoms of orthostatic intolerance including palpitations, light headedness, weakness and blurred vision

• Dissociative neurological symptom reaction (DNSR- formerly conversion disorder)

If they are seen following vaccination, the vaccination is probably a contributing stress adding to an accumulation of stressful factors or health issues.

If you have access to the New Zealand Doctor newspaper, see also: M Hart, A Brass, S Kininmonth (2021) Immunisation stress responses and anaphylaxis: What’s the difference?