Effectiveness of varicella vaccines as postexposure prophylaxis.
BACKGROUND
Although chickenpox is usually a mild disease, it is not always free of complications, especially in adolescents and adults. Previous studies of postexposure prophylaxis conducted with experimental vaccines showed the vaccine to be highly effective if administered in the first 3 to 5 days after exposure. However, studies carried out with commercialized vaccines yielded discordant results. The aim of the present study was to assess the effectiveness of currently available varicella vaccines as postexposure prophylaxis.


METHODS
We conducted a prospective cohort study. Patients susceptible to chickenpox consulting at the Preventive Medicine Department of the Vall d'Hebron Hospital after household exposure to a case of chickenpox were included. Postexposure prophylaxis with varicella vaccine was administered within the first 5 days after contact. Subjects were interviewed by telephone between 4 and 8 weeks after vaccination to ascertain whether chickenpox had appeared and, if so, its severity. The effectiveness of the vaccine in preventing and attenuating the disease was calculated with a confidence interval of 95%.


RESULTS
Sixty-seven subjects were included in the study. Effectiveness of the varicella vaccine in preventing any type of disease was 62.3% (CI 95%: 47.8-74.9) and 79.4% (CI 95%: 66.4-88.9) in preventing moderate and severe disease. No statistically significant differences were found when effectiveness was compared according to sex, age, or days elapsed since exposure.


CONCLUSIONS
Administration of varicella vaccines within the first 5 days postexposure is effective in preventing chickenpox and in attenuating the illness.
Brotons
Maria
M
Servicio de Medicina Preventiva y Epidemiología, Hospital Universitario Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain.
Campins
Magda
M
Méndez
Leonardo
L
Juste
Concepción
C
Rodrigo
Jose Angel
JA
Martínez
Xavier
X
Hermosilla
Eduardo
E
Pinós
Laia
L
Vaqué
Josep
J
D000293:Adolescent; D000328:Adult; D002644:Chickenpox / Q000276:immunology / Q000517:prevention & control*; D019433:Chickenpox Vaccine / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005192:Family Health; D005260:Female; D006801:Humans; D007223:Infant; D007407:Interviews as Topic; D008297:Male; D056990:Post-Exposure Prophylaxis / Q000379:methods*; D011446:Prospective Studies; D016896:Treatment Outcome; D055815:Young Adult
D019433:Chickenpox Vaccine