Changing seroprevalence of varicella zoster virus infection in a tropical city state, Singapore.

OBJECTIVE

To understand the seroepidemiology of varicella zoster virus (VZV) in the Singaporean population, based on a paediatric survey conducted in 2008-2010 and the 2010 National Health Survey. The findings were compared with previous studies carried out in 1989-1990, 1993, 1998, and 2004.

METHODS

The paediatric survey involved 1200 subjects; residual diagnostic serum samples were collected from Singapore residents aged 1-17 years at two hospitals. The adult survey involved 3293 subjects; residual serum samples were obtained from Singapore residents aged 18-79 years who had participated in the 2010 National Health Survey.

RESULTS

The seroprevalence in children under 5 years of age increased from 4% in 1989/1990 to 11.7% in 1998 and 33.2% in 2008-2010. For children aged 5-14 years, the corresponding seroprevalences were 22.8%, 59.5%, and 58.0%. The seroprevalence in children aged 5-14 years in 2008-2010 was not significantly different from that in 1998 (p=0.721). Among Singapore adults over 25 years of age, the seroprevalence remained consistently high at around 88% from 1998/1990 to 2010.

CONCLUSIONS

Nearly two-thirds of pre-school children, 39.5% of primary school children, and 29% of adolescents aged 13-17 years are susceptible to VZV infection. At this level of immunity, it can be expected that outbreaks will continue to occur unless the varicella vaccine is introduced into the national childhood immunization programme.