Successes and challenges in varicella vaccine

Abstract

Varicella is a highly contagious disease caused by primary infection with varicella zoster virus (VZV). VZV infection, as well as varicella vaccination, induces VZV-specific antibody and T-cell-mediated immunity, essential for recovery. The immune responses developed contribute to protection following re-exposure to VZV. When cell-mediated immunity declines, as occurs with aging or immunosuppression, reactivation of VZV leads to herpes zoster (HZ). It has been almost 20 years since universal varicella vaccination has been implemented in many areas around the globe and this has resulted in a significant reduction of varicella-associated disease burden. Successes are reviewed here, whilst emphasis is put on the challenges ahead. Most countries that have not implemented routine childhood varicella vaccination have chosen to vaccinate high-risk groups alone. The main reasons for not introducing universal vaccination are discussed, including fear of age shift of peak incidence age and of HZ incidence increase. Possible reasons for not observing the predicted increase in HZ incidence are explored. The advantages and disadvantages of universal vs targeted vaccination as well as different vaccination schedules are discussed.

Seropositivity of Varicella zoster virus in vaccinated Korean children and MAV vaccine group

“…3,[12][13][14] Although this decreased the morbidity and mortality due to varicella, outbreaks were frequently reported among the vaccinated population. [15][16][17] The controversial causes of breakthrough infections were the age at vaccination, vaccine type, primary vaccine failure (not mounting protective immunity), or secondary vaccine failure (waning of protective immunity).…”

“…Varicella usually affects children aged 2-8 y. [1][2][3] Based on the universal nomenclature for VZV, VZV is categorized into 5 clades (clades [1][2][3][4][5]. While clades 1, 3, and 5 are common in Europe, clade 2 is most widely distributed in Japan and East Asia.…”

Prevention of Herpes Zoster and its complications: From clinical evidence to real life experience

“…58 A model-based evaluation on the impact of varicella immunization on HZ in Italy has shown that an increase of HZ incidence related to varicella extensive immunization should be not certain. 59 In conclusion, evidence of an increase of HZ in countries with a universal varicella vaccination program is not consistent; 60 many studies have shown evidence of increasing incidence trends in HZ in countries with or without a universal varicella vaccination program. 61,62,63 Besides, in some countries, HZ incidence started to increase years before the vaccine was introduced.…”

Estudo Clínico-Epidemiológico da Infeção Complicada por Vírus Varicela-Zoster na Idade Pediátrica

“…Ao longo do tempo tem-se assistido a um aumento da incidência da varicela nas crianças 1 com cerca de 95% dos adultos imunes na faixa etária dos 20 -29 anos. 2 Geralmente apresenta uma evolução auto-limitada e benigna, contudo pode associar-se a complicações e a necessidade de internamento em cerca de 2-6% dos casos. [3][4][5] A complicação mais frequentemente descrita é a sobreinfeção bacteriana da pele e tecidos moles, cujos agentes mais envolvidos são o Staphylococcus aureus e o Streptococcus pyogenes.…”