Who is vaccinated with the zoster vaccine? A population-based study in Stockholm county
Herpes zoster has an incidence of around 3 per 1000 person years in Sweden, which equivocates to around 6000 new cases in Stockholm County every year. The incidence of herpes zoster increases after the age of 50 due to a decline in cell-mediated immunity, with its peak in individuals over the age of 80. Herpes zoster is more common in women and immunocompromised individuals. It has been estimated that the lifetime risk of viral reinfection is about 20-30%.
A vaccine against herpes zoster was approved by FDA in 2006. Initially it was only recommended for use among over 60 year olds, however in 2011 it was also approved for use in 50-59 year olds. This vaccine, Zostavax, is considered to act as a booster on the cell-mediated immune response. Hence, preventing reactivation of the latent varicella virus infection. Zostavax has been available in Sweden since September 2013 and is recommended to individuals 50 years and older. In June 2014, approximately 13000 doses of the vaccine had been sold with 60% of those being administered in Stockholm County. Currently there are no official recommendations or campaigns for vaccination against herpes zoster, which makes it difficult to ascertain which individuals are choosing to be vaccinated and whether, for example, the over 50’s population is being reached.
We therefore propose to carry out a study to describe and characterise individuals, living in Stockholm County, who have been vaccinated with Zostavax between September 2013 and September 2014. These individuals will be compared with a randomly selected age, sex and municipality matched sample of the general population also residing in Stockholm County. We will utilise population-based health-care registers in Stockholm County and Statistics Sweden to undertake this study.