Comparison of varicella history with presence of varicella antibody in refugees
Introduction
Varicella zoster virus (VZV) caused approximately 4 million cases of chicken pox each year in the United States before widespread use of varicella vaccine. Since licensure of the vaccine in 1995, incidence of disease and hospitalizations associated with complications of varicella have decreased by 80% [1]. Further reductions in disease incidence will depend upon achieving and maintaining high vaccine coverage through routine childhood immunization and identifying and protecting by immunization older individuals who remain susceptible to varicella.
Immigrants entering the United States rarely have received varicella vaccine and may represent a group likely to be susceptible to varicella. Varicella infection tends to occur later in life in the tropics than in temperate climates such as the United States, leaving adolescents and young adults susceptible [2]. Currently, in the United States, a negative or uncertain history of varicella is used to identify those in need of vaccine, and a positive history is considered adequate evidence of immunity, a strategy based on reliability of history of varicella in US individuals [3]. We compared history of varicella in newly arrived refugees with results of testing for antibody to varicella to assess reliability of history of varicella in this population. These data are necessary for analyses of cost-effectiveness of different immunization strategies and in planning public health interventions to eliminate varicella in the US.
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Patient population
Refugees 7 years of age and older who completed a comprehensive health assessment at Boston Medical Center within 3 months of arrival in the US were eligible for this study. Information collected from the medical record included age, countries of origin and recent residence, history of clinical varicella, and history of varicella immunization. All patients were seen with interpreters if not fluent speakers of English. “Chicken pox” or “varicella” was translated by trained hospital interpreters,
Patient population
A total of 1164 refugees were included in the study; serology results were available for 1156 (99%). The median age was 26 years with a range of 7–87 years. Fifty-four percent of subjects were male. Seroprevalence of varicella by age and countries/regions of origin of patients is shown in Table 1.
Of 1156 refugees who were tested for presence of varicella antibodies, 872 (75%) were positive. The prevalence of varicella antibody varied from 70% in 248 subjects from Sub-Saharan Africa to 82% in
Discussion
History of varicella was not a reliable predictor of varicella antibody status in this refugee population. A positive history of clinical varicella correlated better with presence of antibody to varicella than a negative history of varicella with lack of antibody, a finding consistent with other studies. In US young adult army recruits and Swiss children and adolescents the positive predictive value of history of clinical varicella ranged from 97 to 98.5% [4], [5], [6]. Lieu and colleagues
Conclusion
Screening refugees for antibody to varicella upon arrival to the US and immunizing those who are susceptible would optimize varicella immunity in refugees. For other immigrants, screening done at first encounter with the US primary care system followed by immunization as needed would be ideal. If this is not done because of logistical or financial barriers, other opportunities for doing so include primary care visits, school or college entry, employment medical evaluation, and medical
References (17)
- et al.
Serotesting versus presumptive varicella vaccination of adolescents with a negative or uncertain history of chickenpox
J. Adol. Health.
(2001) Letter to the editor
Vaccine
(2002)- et al.
Prevention of chickenpox in reproductive-age women: cost-effectiveness of routine prenatal screening with postpartum vaccination of susceptibles
Obstetr. Gynecol.
(1998) - et al.
Cost effectiveness of vaccination strategies in adults without a history of chickenpox
Am. J. Med.
(2000) - et al.
Varicella disease after introduction of varicella vaccine in the United States, 1995–2000
JAMA
(2002) Varicella zoster infections
In: A World Guide to Infections
(1991)- et al.
Varicella vaccination—a critical review of the evidence
Arch. Dis. Child.
(2001) - et al.
The susceptibility of young adult Americans to vaccine-preventable infections
JAMA
(1991)