Herpes zoster infection, vaccination and immunocompromised rheumatology patients
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- O’Connor, M.B. & Phelan, M.J. Rheumatol Int (2013) 33: 239. doi:10.1007/s00296-011-2155-9
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Varicella is a self-limiting and relatively mild disease of childhood, although it is frequently more severe and complicated among the immunocompromised rheumatology patients on immunomodulator therapies. In addition, future reactivation of the dormant virus in dorsal root ganglia may cause herpes zoster infection, which can be very debilitating. In this manuscript, we discuss the nature of this infection along with its potential vaccine especially among rheumatology patients.
KeywordsHerpes zoster infectionVaccinationImmunocompromisedRheumatology patients
Varicella is a self-limiting and relatively mild disease of childhood, although it is frequently more severe and complicated among neonates (severe neonatal varicella), adults, pregnant women (potentially leading to congenital varicella syndrome in the child) and the immunocompromised rheumatology patients on immunomodulator therapies. In addition, after an initial infection, the varicella zoster virus (VZV) lays dormant in dorsal root ganglia and may reactivate with declining cellular immunity to cause herpes zoster, particularly in the elderly and immunocompromised individuals .
There are two methods of varicella infection control using immunisation: post-exposure passive antibody prophylaxis in the form of varicella zoster immunoglobulin (VZIG or VARITECT) and active vaccination. The varicella vaccine, which was developed in the early 1970s using a live attenuated form of the varicella zoster virus , has been licensed for use in some countries since the mid-1980s and has been part of the routine childhood immunisation schedule in the United States (US) since 1995 . The cost-effectiveness of mass vaccination against varicella has, however, been questioned . Universal vaccination programmes may cause an increase in the average age of infection, which may lead to increased adult morbidity and incidence of congenital varicella syndrome (CVS) and severe neonatal varicella. Studies have also suggested that re-exposure to exogenous varicella zoster virus protects against herpes zoster ; thus, a reduction in the transmission of VZV (through vaccination) could result in an increased incidence of zoster.
Since its development in the early 1970s, the VZV vaccine has been licensed in numerous countries and incorporated into the US routine childhood immunisation schedule. Many European countries have targeted VZV vaccination of susceptibles for whom VZV infection poses a particular risk either to themselves (e.g. immunocompromised rheumatology patients) or to others (e.g. healthcare workers), with many more considering introducing either targeted or mass childhood immunisation. Germany is the only country to have recently incorporated VZV vaccination into their routine childhood immunisation schedule. Cyprus, Israel and Lithuania currently recommend VZV vaccination for children, and routine mass childhood immunisation has already been introduced in the Sicily region of Italy.
As with most universal mass vaccination, childhood immunisation against VZV could have a negative impact should it be introduced without sufficient coverage to induce herd immunity. Low vaccine coverage can result in an increase in the average age of primary infection, with a concomitant increase in severity of varicella in adult age groups, and especially in pregnant women, where infection can have adverse sequelae for both the mother and unborn child. The levels of coverage estimated in countries with current VZV vaccination (approximately 25%) will have little impact on the age distribution of disease . However, with increasing coverage, morbidity among adults is likely to increase, and vaccination is only predicted to decrease morbidity in both adults and children at around 70% coverage . Thus, it is important that universal vaccination against VZV is introduced in a region or country only if the attainment of very high coverage can be assured. Furthermore, it is important that the age distribution of varicella disease is monitored, and this is best done through case-based surveillance of varicella.
Many countries have opted to limit vaccination to specific groups who are at increased risk of developing severe varicella disease or infecting risk groups (for example, immunocompromised rheumatology patients). Targeted strategies have been predicted to have little impact on varicella incidence  and, consequently, are predicted to have little impact on herpes zoster, and the age distribution of primary disease . Mass vaccination against VZV should be introduced only if very high coverage can be assured. With the introduction of routine childhood immunisation against VZV, however, adequate surveillance systems for both varicella and herpes zoster are advisable.
Therefore due to current practice and knowledge, the debate of VZV vaccination remains controversial among immunocompromised rheumatology patients such as those receiving methotrexate and/or concomitant biological therapies. We await developments and clear guidelines surrounding this topic in the coming years.