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 (χ2 = 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.