Susceptibility of cadets and recruits to chickenpox: A seroprevalence study

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.

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.

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%.

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.