A number of adolescent females who had been administered Gardasil™ vaccine (against human papilloma virus) became ill during May 2007 in Melbourne. The young persons were thought to have reacted to the vaccine adversely. The media soon ran with the story in newsprint, local radio and television. A number of authoritative figures assured the public that the vaccine was safe. No-one really explained why these young persons were sick if the vaccine was safe.
It is likely that all or virtually all the individuals were suffering from a well-documented condition called mass psychogenic illness. Their symptoms were real – they were not imagining them. It was their body's way of coping with the stress of the moment. This unusual adverse event following immunisation involves physiological reactions in response to a psychiatric stimulus. When vaccines are administered to groups, the physical reactions of the recipients may be similar, causing a form of mass reaction, the mechanism for which is the same as that for mass reactions from other causes. These phenomena have been categorised as mass psychogenic illness (MPI), and have been defined as the collective occurrence of a constellation of symptoms suggestive of organic illness, but without an identified cause, in a group of people with shared beliefs about the cause of the symptom(s). A review of the literature shows that such outbreaks have been reported in differing cultural and environmental settings, including developing and industrialised countries, in the workplace, on public transport, in schools and the military.1,2 The perceived threats have been against agents such as food poisoning, fire and toxic gases. Whatever the place or perceived threat, the response seems to be similar. The symptoms generally included headache, dizziness, weakness and loss of consciousness.
Once under way, MPIs are not easy to stop. Incidents reported in the literature show that they can quickly gather momentum and can be amplified by the press which disseminates information rapidly, escalating the events. Management of such mass events can be extremely difficult. Should the public health official in charge continue to try and determine the cause, or should this person call off the entire investigation? It is suggested that once vaccines are identified as a probable cause of the phenomenon, a dismissive approach may actually be harmful. Unless the spokesperson has already earned a high level of trust, the public is not likely to be easily convinced that nothing was wrong with the vaccine.
An increased awareness of MPIs on the part of organisers of future mass vaccination campaigns seems appropriate. Immunisation managers should be aware that mass immunisation campaigns could generate such mass reactions. A mass campaign using Gardasil™ among adolescents was always likely to trigger such a reaction, and organisers of future campaigns should bear this in mind.