Measurement of antibodies to varicella-zoster virus in a tropical population by enzyme-linked immunosorbent assay

Susceptibility of cadets and recruits to chickenpox: A seroprevalence study

Background

Regular outbreaks of chickenpox are reported among cadets and recruits in the army undergoing training, resulting in morbidity and loss in terms of training days. Vaccination policy in the army mandates that all cadets and recruits be vaccinated against chickenpox on joining the training centers. However, 100% vaccination of trainees is not achieved. Hence, seroprevalence data among cadets and recruits were collected with the aim to assess the need for vaccination against chickenpox.

Methods

The data were collected from cadets and recruits undergoing training in military training centers by simple random sampling. Blood samples were collected from all study participants for IgG enzyme-linked immunosorbent assay for varicella zoster. A structured questionnaire was also used to collect information from all participants.

Results

A total of 2041 cadets and recruits between the ages of 19-29 years were studied of which 96.1% were males. Of all participants, 49.9% were seropositive showing varicella zoster virus (VZV) IgG antibody in the serum, and 29.1% study participants gave positive history of having had varicella in the past. The sensitivity of definite positive history of varicella when compared with presence of VZV IgG antibodies was found to be 55.50% while specificity was found to be 97.17%.

Conclusion

A very large majority of cadets and recruits that joined the army are susceptible to chickenpox. Hence, the risk of repeated chickenpox outbreaks in these training centers remains very high. As the sensitivity of history of past infection of chickenpox is relatively low, it cannot be used as a tool to determine the susceptibility of the trainees to the infection.

Chicken pox infection in patients undergoing chemotherapy: A retrospective analysis from a tertiary care center in India

There is paucity of data on the incidence, severity and management of chicken pox in patients receiving active chemotherapy for cancer. From October 2010 to October 2011, patients were included in this study if they developed a chicken pox infection during their chemotherapy. The details of patients' cancer diagnosis and treatment along with clinical and epidemiological data of the chicken pox infections were assessed from a prospectively maintained database. Twenty-four patients had a chicken pox infection while receiving chemotherapy and/or radiotherapy. The median age of the patients was 21 years, and two-thirds of the patients had solid tumor malignancies. Overall, eight (33%) patients had complications, six (25%) patients had febrile neutropenia, four (17%) had diarrhea/mucositis, and four (17%) had pneumonia. The median time for recovery of the infection and complications in the patients was 9.5 days (5-29 days), whereas for neutropenic patients, it was 6.5 days (3-14 days). The median time for recovery from chicken pox infections in neutropenic patients was 10 days (5-21 days), compared with 8.5 days (0-29 days) in non-neutropenic patients (P=0.84). The median time for recovery from infections was 8.5 days in patients with comorbidities (N=4), which was the same for patients with no comorbidities. The clinical presentation and complication rates of chicken pox in cancer patients, who were on active chemotherapy, are similar to the normal population. The recovery from a varicella infection and complications may be delayed in patients with neutropenia. The varicella infection causes a therapy delay in 70% of patients. Aggressive antiviral therapy, supportive care and isolation of the index cases remain the backbone of treatment.

Varicella immunity in Iran: an age-stratified systematic review and meta-analysis

OBJECTIVES

To generate synthesized information on the epidemiology of VZV infection, as well as an estimation of prevalence of age-specific antibody in Iranian less than 40.

MATERIAL AND METHODS

After exclusion of irrelevant and overlapping reports, 15 papers were included (from nine major cities). Studies were pooled according to the heterogeneity test results. Random effect model methods were used for meta-analysis where significant heterogeneity was observed (age 1-16years).For other age groups, fixed model were used.

RESULTS

Significant heterogeneity was observed in prevalence rates of all childhood age-groups. The seropositivity prevalence increased steeply from the age of 1-5 to 6-10 [from 21.9% (95% CI; 10.8-33.1) to 42.1 %(95% CI; 33.6-50.6)]. At the age of 11 15, 59.4% (95% CI; 46.1-72.8) of children showed to be infected. The rate of seropositivity was more than 87% in individuals of 40 and older.

CONCLUSION

The varicella seroeprevalence in Iran is in accordance with average tropical and temperate areas. Comparison of conducted studies during 2003 to 2011 didn't show any alteration in VZV seroprovalence in Iran.

Time trends in pediatric hospitalizations for varicella infection are associated with climatic changes: a 22-year retrospective study in a tertiary Greek referral center

BACKGROUND/AIMS

The transmission rate of air-borne infectious diseases may vary secondary to climate conditions. The study assessed time trends in the seasonality of hospitalized varicella cases in a temperate region in relation to climatic parameters prior to the implementation of universal varicella immunization.

METHODS

A retrospective descriptive study was conducted among all pediatric and adolescent varicella patients (n = 2366) hospitalized at the "Aghia Sophia" Children's Hospital during 1982-2003 in Athens, Greece. Date of infection was computed based on hospital admission date. Seasonal and monthly trends in the epidemiology of varicella infection were assessed with time series analysis (ARIMA modeling procedure). The correlation between the frequency of varicella patients and the meteorological parameters was examined by the application of Generalized Linear Models with Gamma distribution.

RESULTS

During 1982-2003, the occurrence of hospitalized varicella cases increased during summer (p = 0.025) and decreased during autumn (p = 0.021), and particularly in September (p = 0.003). The frequency of hospitalized varicella cases was inversely associated with air temperature (p<0.001). In contrast, the occurrence of hospitalized varicella cases was positively associated with wind speed (p = 0.009).

CONCLUSIONS

Pediatric hospitalizations for varicella infection rates have increased during summer and decreased during autumn in the examined temperate region. Time trends in hospitalized varicella cases are associated with climatic variables.

Study of susceptibility towards varicella by screening for the presence of IgG antibodies among nursing and medical students of a tertiary care teaching hospital in pune, India

BACKGROUND

It is believed that all suffer from chickenpox infection in their childhood. Many studies abroad and some in India clearly indicate that many individuals escape the infection in childhood, and thus, remain susceptible in adulthood. Adulthood chickenpox is a more serious infection than childhood. Prior screening of health care workers for the presence of IgG antibodies against Varicella will not only prevent hospital outbreaks but also economic and academic loss faced by the students. This will also have an important implication in terms of patient care as there is a threat of spreading Varicella to immuno-compromised patients. Definite history of prior infection of chickenpox is considered as an indicator for immunity towards the same. However, the reliability of this needs to be tested.

AIM

A study to assess the susceptibility of nursing and medical students towards Varicella infection by screening for IgG antibodies against Varicella virus and to identify any risk factors for the same.

SETTINGS AND DESIGN

A hospital-based cross-sectional study in nursing and medical students.

MATERIALS AND METHODS

Total 78 nursing and medical students participated in the study. They were given prestructured and pretested questionnaires. After obtaining informed consent, blood sample was collected and screened for the presence of IgG antibodies against Varicella by Enzyme Linked Immunosorbent Assay (ELISA) by using a commercial kit.

STATISTICAL ANALYSIS

Epi_info 2002 was used for analysis. Age of the study subjects were summarized as mean age and standard deviation. Susceptibility was analyzed as percentage with 95% confidence interval and Chi Square test was used to find association of susceptibility status with sex and region of residence in childhood. Relevance of definite history as an indicator for immunity was assessed by calculating sensitivity, specificity, positive and negative predictive values with 95% confidence interval.

RESULTS

Twenty males (25.6%) and 58 females (74.4%) participated in the study from medical and nursing students. The mean age ± standard deviation of mean was 19.4 ± 1.42 years for female students and 20.8 ± 2.13 years for male students. Total 20 (25.6%) students were found to be susceptible to Varicella with the confidence interval ranging from 15.8% to 35.4%. With respect to the gender of the students, the difference between the susceptibility percentage in female students (32%) and in male students (14.3%) was only a numerical difference and not statistically significant (χ(2) = 2.098, P=0.147, d.f. = 2). Also, the susceptibility was seen significantly more among Keralite students (Pearson Chi-Square=16.736, d.f=6, P=0.008; Likelihood Ratio=15.086, d.f=6, P=0.035; Fisher's Exact Test=13.569, p=0.022). The sensitivity of definite history of prior chickenpox infection as an indicator of immunity was only 55.17%, with C.I ranging from 43.9% to 66.4%, specificity was 80%, with C.I. ranging from 70.9% to 86%, and positive predictive value was 88.8% with C.I of 81.7% to 89% and negative predictive value of history of 66.6% with C.I. of 56% to 77.2%.

CONCLUSION

Total 20 (25.6%) students were found to be susceptible to Varicella with the confidence interval ranging from 15.8% to 35.4%. Thus, there is a need for vaccination of all susceptible individuals. Definite history of prior chickenpox infection is not a reliable indicator of immunity against the same. The investigators recommend screening for IgG antibodies against Varicella of all students selected for the M.B.B.S. (Bachelor of Medicine and Bachelor of Surgery) and nursing course, and vaccination for susceptible individuals to prevent institutional outbreak and academic loss.

Prevalence of varicella-zoster antibodies in pregnant women in Catalonia (Spain). Rationale for varicella vaccination of women of childbearing age

OBJECTIVE

The objective of this study was to determine the prevalence of antibodies against varicella-zoster virus (VZV) in pregnant women in Catalonia (Spain).

SETTING

The prevalence of antibodies against VZV was assessed in a representative sample (n = 1522) of pregnant women of Catalonia obtained in 2003.

METHOD

The sample was obtained including all women attended for childbirth, during 2 months of 2003, in 27 randomly selected hospitals with maternity clinics.

MAIN OUTCOME MEASURES

Varicella-zoster antibodies were determined using the enzyme-linked immunosorbent assay test.

RESULTS

The total number of women included in the study was 1522, corresponding to a participation rate of 83%. The prevalence of varicella-zoster antibodies in pregnant women was 96.1% (95% CI 95.1-97.1). The prevalence of antibodies was 94% in pregnant women aged 15-24 years, 95% in those aged 25-29 years and >95% in those aged 30-49 years. The prevalence of antibodies was not associated to the place of birth, place of residence (urban or rural), educational level and social class. The study showed that 6% of pregnant women aged 15-24 years and 5% of those aged 25-29 years were susceptible to varicella-zoster infections in Catalonia (Spain).

CONCLUSION

The study showed that a varicella-zoster vaccination programme aimed at women of childbearing age could be necessary in Catalonia to prevent all varicella-zoster infections during pregnancy.

Safety and immunogenicity of a zoster vaccine in varicella-zoster virus seronegative and low-seropositive healthy adults

OBJECTIVE

To evaluate immunogenicity and tolerability of a live attenuated zoster vaccine in varicella-zoster virus (VZV) seronegative or low-seropositive adults > or = 30 years of age.

STUDY DESIGN

Double-blind, placebo-controlled, randomized, multicenter study. Subjects were enrolled in two stages by prescreened serostatus. Subjects with a low VZV antibody titer (< or = 5 gpELISA units/mL) were enrolled in Stage 1. Subjects with undetecable VZV antibodies and no safety issues identified during Stage 1 were enrolled in Stage 2. All enrolled subjects were randomized 4:1 to receive one dose (approximately 50,000 PFU) of zoster vaccine or placebo and were followed for safety for 42 days postvaccination. Primary objectives/hypotheses: (1) no vaccine-related serious adverse experiences (AE); (2) < or = 1 laboratory-confirmed varicella-like rash with > 50 lesions within 42 days postvaccination.

SECONDARY OBJECTIVE

summarize the VZV antibody response postvaccination.

RESULTS

Twenty-one subjects (age 27 to 69 years; median 34) enrolled (1148 prescreened); 18 (including 4 seronegative subjects) received vaccine and 3 (including 1 seronegative subject) received placebo. Twenty subjects completed the study; one subject withdrew for reasons unrelated to safety. No serious vaccine-related AE or laboratory-confirmed varicella-like rashes with > 50 lesions were reported. In the zoster vaccine group, all 4 of the initially seronegative subjects (age 32 to 36 years; median 33.5) seroconverted and 6 of the 13 (46.2%) initially seropositive subjects had a > or = 4-fold rise in VZV-specific antibody titer at 6 weeks postvaccination.

CONCLUSIONS

The zoster vaccine appears to be immunogenic and generally well tolerated in healthy adults > or = 30 years of age, regardless of initial VZV antibody serostatus.

Seroprevalence of antibody to varicella among Somali refugees

OBJECTIVES

To determine the seroprevalence of varicella antibody among recent Somali refugees living in Olmsted County, Minnesota, and to estimate the risk of varicella-zoster virus (VZV) infection in this group.

SUBJECTS AND METHODS

We obtained blood samples from the study subjects, along with demographic information, immunization records, and vaccine-preventable disease history. Serum samples were tested using a whole-virus IgG VZV-specific commercial enzyme-linked immunosorbent assay kit. This study was completed in 1998.

RESULTS

Overall, 200 Somali refugees, comprising 33 extended families, were interviewed, with 193 providing adequate blood samples. Thirty-five subjects (18%) were seronegative for varicelia. Males had a significantly higher seronegativity rate (25% [n = 23]) compared with females (12% [n = 12]; P = .02); however, this association disappeared after adjustment for age and varicella infection history. Five percent (5/92) of adults were seronegative compared with 30% (30/101) of all children (P < .001). Eight percent (5/61) of the adult females were seronegative, whereas none (0/31) of the adult males were seronegative. Conversely, 38% (23/60) of male children were seronegative compared with 17% (7/41) of female children (P < .001).

CONCLUSION

These results demonstrate a high prevalence of varicella seronegativity among Somali refugees who have immigrated to an endemic area. We recommend instituting improved education regarding varicella among Somali communities and increasing vaccine uptake or routine testing for serum varicella antibody to prevent VZV-related morbidity and mortality, particularly in adolescents, adult refugees, and women of childbearing age.

Safety, tolerability, and immunogenicity of a two-dose regimen of high-titer varicella vaccine in subjects ≥13 years of age

A new manufacturing process, known as process upgrade varicella vaccine (PUVV) was developed for a refrigerated formulation of varicella vaccine and for an investigational zoster vaccine. Safety and tolerability of a two-dose regimen of high-titered (approximately 50,000 PFU) PUVV were compared to a lower-titer formulation (approximately 5400 PFU) of VARIVAX; in 1366 healthy subjects > or =13 years old. Only one vaccine-related clinical serious adverse experience (pruritus; no hospitalization) was reported, in the VARIVAX group. Injection-site adverse experiences following any dose were higher in the PUVV group, 70.0%, than in the VARIVAX group, 56.2%, but generally were mild. Immunogenicity were similar in both groups in seronegative subjects. PUVV was generally well tolerated, and elicited an immune response similar to that induced by the marketed formulation of VARIVAX.

Seroepidemiology of varicella-zoster virus in Bangladesh

Data on the seroprevalence of antibodies protective against the varicella-zoster virus are needed to develop strategies to prevent varicella infections in Bangladesh. Of 1209 patients evaluated at referral-level health facilities in Dhaka, 943 (78%) had no known history of chickenpox and were tested by latex agglutination for the presence of varicella-zoster antibody in serum. Forty-one per cent (386) of the 943 specimens tested were negative. Seropositivity was highest among neonates (83%), declined sharply to 19% in those aged 7-12 months, and thereafter rose steadily with age until a plateau of 85% was reached after the age of 16 years. This first report of varicella-zoster antibody seroprevalence in Bangladesh suggests that, as in other tropical areas, a significant proportion of children, adolescents and adults are susceptible. Children aged from 15 months to early adolescence might be the most important group to target with the vaccine currently available. However, to ensure successful immunisation, further, population-based seroprevalence data are needed, as are an assessment of the vaccine's acceptability and the accessibility of the target population. Incomplete coverage of young children could result in delayed acquisition, and, ultimately, in more severe disease.

High seroprevalence of antibodies to varicella zoster virus in adult women in a tropical climate

OBJECTIVES

To determine whether the seroprevalence of antibodies to varicella zoster virus (VZV) in adults is similar to that reported in tropical populations elsewhere.

METHODS

We measured the seroprevalence of VZV IgG antibodies, using an enzyme immunoassay (EIA) in women attending an antenatal clinic in an urban centre in tropical Australia.

RESULTS

The overall seroprevalence of VZV antibodies in 298 women was 92% (95% CI 88-95), with no difference between women who spent their childhoods in the tropics and colleagues. None of the overseas-born women was seronegative.

CONCLUSION

The seroprevalence of VZV antibodies in this tropical population in Australia is as high as that reported from temperate regions, suggesting that social and cultural factors and population mobility are more important determinants of age distribution of VZV immunity than tropical climate.

Geographic similarities between varicella and multiple sclerosis: an hypothesis on the environmental factor of multiple sclerosis

The environmental factor causing multiple sclerosis (MS) is unknown. Kurtzke et al. (Neurology 1979; 29: 1228-1235) depicted a north to south diminishing gradient in the case/control ratios for MS among American veterans in the United States. A similar, but less precise, gradient emerged when the incidence rates of varicella from 37 states during 1978-91 were compared. A loose correlation appears to exist between the mean incidence of varicella and the MS risk ratio (n = 0.344 Spearman rank correlation coefficient, p = 0.037). Further, the data on the fat of migrants moving from a high risk MS country to a low risk country and the reverse, plus the great importance of the age at migration, raise the question of a possible connection between the two diseases. Because of these epidemiological and other similarities between the two diseases a further comparative study was suggested.

The age of infection with varicella-zoster virus in St Lucia, West Indies

Sera from an age-stratified sample of 1810 people from the Caribbean island of St Lucia were tested for antibodies against varicella-zoster virus. The results indicate that very few infections occur in childhood, which agrees with clinical survey data from other tropical countries, but contrasts with the observed high case rate in children in temperate countries. The alternative hypotheses which may explain these results are discussed, and it is suggested that high ambient temperatures interfere with the transmission of the virus. Irrespective of the cause, the pattern of varicella incidence observed has important implications for any vaccination policy adopted in tropical countries.

Varicella among immigrants from the tropics, a health problem

The incidence of varicella in Tamil refugees in Denmark was evaluated. Of 256 Tamils, 44% developed varicella infection in the first few months after arrival, representing 38% of the adults, and 68% of the children. During approximately four months' observation in Denmark, 75% of the refugees with no history of varicella developed a typical infection whereas only 2% of those with a history of varicella developed the disease. Tropical refugees with a negative history of varicella must therefore be considered nonimmune. Nine of 44 fertile women were pregnant. Two acquired the varicella infection during the first-trimester, none in relation to delivery. By organizing a health-check on arrival, prophylactic measures can reduce the health hazard of varicella infection in refugees from the tropics.

Comparison of five assays for antibody to varicella-zoster virus and the fluorescent-antibody-to-membrane-antigen test

Three commercially available assays (the Varicelisa Test Kit [Whittaker M.A. Bioproducts, Walkersville, Md.], the VZV Indirect Fluorescent-Antibody Test [Electro-Nucleonics, Inc., Columbia, Md.], and the Litton VZV Bio-EnzaBead Screen Kit [Litton Bionetics, Inc., Charleston, S.C.]) and two enzyme-linked immunosorbent assays used in our laboratory, one using a membrane-associated antigen and the other using a soluble antigen dotted on nitrocellulose paper, were compared with a varicella-zoster virus antibody reference assay, the fluorescent-antibody-to-membrane-antigen test. All of the assays compared favorably to the fluorescent-antibody-to-membrane-antigen test when evaluated for sensitivity (0.95), specificity (0.84), and test-retest reliability (79 to 96%), except for the Litton assay, which demonstrated significantly different results for all of the parameters tested (0.55, 1.0, and 69%, respectively).