Global Vaccine Safety

Clusters of anxiety-related reactions following immunization

Extract from report of GACVS meeting of 2-3 December 2015, published in the WHO Weekly Epidemiological Record of 22 January 2016

Clusters of anxiety-related reactions following immunization have affected immunization programmes in several countries and drawn the attention of media and the public globally. Understanding such events, their characteristics, and why they may occur will help to better guide public health efforts to prevent and manage them.

The Committee was provided with updated information on the occurrence of such events in the relevant scientific literature and the media and social media reports from several countries including: Iran (tetanus toxoid vaccine 1992); Italy (hepatitis B vaccine 1995); Jordan (diphtheria tetanus vaccine 1998); India (tetanus toxoid vaccine 2001); Viet Nam (oral cholera vaccine 2001); Australia (HPV vaccine 2007); Taiwan, China (H1N1 influenza 2009); and the United States of America (H1N1 influenza 2010). The GACVS observed that these clusters occurred in rural and urban settings both in high and low income countries from all continents and involved different vaccines. Children of both sexes were affected, though with a higher frequency of girls than boys in some studies. Occurrence of reactions was usually within the first 15 minutes of vaccination and involved mostly school-age children. The reactions manifested with a wide variety of symptoms. Most clusters involved introduction of a new vaccine or a change in the routine programme such as new age group or new setting. A small cluster that started in a group setting could spread quickly to form a larger outbreak involving several clusters. Response to such clusters varied in different countries, as did its impact on vaccination programmes. Public health interventions to regain community trust after such events were often costly and resource-intensive.

A survey carried out in 12 low and middle income countries in October 2015 found that many countries are aware of such events. Fainting events are most commonly reported. The survey also found that short-term consequences included a decrease in public confidence in vaccines, resulting in decreased coverage and concerns and fear among health-care personnel to vaccinate; however, there were no long-term or major impacts on their immunization programmes, mainly due to prompt responses. It was observed that there are gaps in surveillance systems for adverse events following immunization (AEFI) in countries, such that various anxiety-related AEFIs are not well defined and reported or are grouped with other AEFIs, therefore not capturing the true burden.

The use of terms suggesting psychological disorders for severe anxiety reactions were observed to be problematic for vaccinees because of the stigma and consequences that were related to such labelling. Failure to differentiate between the clinical manifestations of fainting, anxiety and associated hyperventilation and other conditions such as anaphylaxis, resulted in mismanagement of cases and thereby additional avoidable harm.

GACVS also reviewed in detail the cluster immunization anxiety reactions that recently occurred on the occasion of a mass measles immunization campaign in a European country. There are increasing reports of occurrence of such reactions with expansion of age of immunization to school children and young adults. Little knowledge and understanding of such events by health workers was also documented. Fast spreading of rumours, fears and concerns of “unknown events” through media and social networking using modern communication technologies was observed and may have aggravated the situation. These events have high visibility and, if not adequately assessed and managed, can convert from a cluster of immunization anxiety events that can be easily managed onsite into a real medical problem with a detrimental impact on the individual affected and on the immunization programme. It was observed that good pre-campaign preparation, such as creating awareness of such events and training of health staff, engagement of communities and appropriate media and communication strategies were important for prevention of such events.

GACVS acknowledged that the magnitude of the impact of immunization anxiety reactions is not currently recognized in the medical literature. Several gaps have been identified including the need for case definitions that span the different degrees of anxiety reactions and for guidance on how to recognize, manage and prevent immunization anxiety reactions. It is also important to identify communication strategies tailored to the audience and plan interventions for first responders, hospitals and immunization programmes in order to improve recognition and management of immunization anxiety clusters, and limit their continuation and spread. There is need to conduct research on predisposing factors for such clusters, outbreaks and the role of social media. Other key areas that need to be addressed include defining effective practices for prevention and intervention in different settings. It was also noted that such clusters need not be immunization-specific and may occur in several other contexts. Finally, GACVS also noted that lack of recognition, lack of early onsite intervention, excessive hospitalization and overreaction by health-care providers and programme managers to such episodes have the potential to aggravate the problem.