Mass psychogenic illness following oral cholera immunization in Ca Mau City, Vietnam.
BACKGROUND
Targeted cholera immunization of high-risk populations in Vietnam is conducted based on routine surveillance data. Following mass immunization of schoolchildren in Ca Mau City using an oral bivalent killed cholera vaccine, adverse reactions were noted.


METHODS
Salient data were collected in a systematic fashion including the review of medical records; interview of the school principal, teachers, students, parents and doctors; and review of the storage and handling of the vaccine.


RESULTS
On 18 December 2001, 234 children at a primary school in Ca Mau City received the cholera vaccine. Within 1h of immunization, three children in one of the classrooms complained of trembling, nausea and headache and were brought to the library and soon other children followed. Out of 234, 97 (42%) pupils were affected and brought to the Municipal Health Center or Ca Mau Provincial Hospital. Those who were affected were younger (mean age=9.6 years; 95% CI=9.4-9.7) compared to those who were not affected (mean age=10 years; 95% CI=9.7-10.3; t-test=-2.4; P-value=0.02). The proportion of affected females among those who had received the vaccine (49/114 or 43%) was similar to the proportion in males (48/120 or 40%; RR=1.07; 95% CI=0.79-1.46). The most frequent presenting complaint was cold extremities (60%) followed by headache (27%). All affected children recovered and were discharged in a few hours. None reported any sequelae or relapse. Once the situation was recognized, the cholera immunization campaign was continued. Laboratory tests of vaccine samples from the same batch detected no abnormality or contaminating agent.


CONCLUSIONS
The findings suggest that the children at primary school number 1 suffered from a mass psychogenic illness. This incident was unusual in that a similar number of boys and girls were affected, in contrast to the frequently reported preponderance of female cases. Furthermore the underlying cause was very quickly diagnosed, medical interventions were kept to a minimum, and no relapse was observed. Future vaccination campaigns have to assure that the families are informed in advance.
Pasteur Institute, 167 Pasteur Street, District 3, Ho Chi Minh City, Viet Nam.
Ha Ba
HB
Khiem
Le Dinh
le D
Huan
Nguyen Thi Minh
NT
Phuong
Dang Hai
DH
Dang
Do Huy
DH
Hoang
Le Thanh
le T
Phuong
Pham Kim
PK
Sac
Tran Minh
TM
Chien
Luu Anh
LA
Tai
Nguyen Thanh
NT
Dan
Jacqueline L
JL
Deen
Lorenz von
Lv
Seidlein
John
J
Clemens
Dang Duc
DD
Trach
D000284:Administration, Oral; D002648:Child; D022121:Cholera Vaccines / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D006261:Headache / Q000209:etiology; D006801:Humans; D008297:Male; D009325:Nausea / Q000209:etiology; D011602:Psychophysiologic Disorders / Q000453:epidemiology* / Q000209:etiology*; D012737:Sex Factors; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000009:adverse effects; D014744:Vietnam / Q000453:epidemiology
D022121:Cholera Vaccines; D015164:Vaccines, Inactivated