If the patient goes into cardiac arrest following an adverse effect to the vaccination - start cardiopulmonary resuscitation (CPR) immediately following current basic life support (BLS) guidelines.
The Resuscitation Council UK website has soem excelent resources for refreshing your knowledge of how to do this. How to do CPR | Resuscitation Council UK contains a video and written instructions for carrying out CPR.
You can find out more about CPR in adults and children by using the following links: