Varicella-zoster virus susceptibility and primary healthcare consultations in Norway.

BACKGROUND: Currently Norway does not recommend universal varicella vaccination for healthy children. This study assessed susceptibility to varicella-zoster virus (VZV) in the Norwegian population for the first time. METHODS: A national convenience sample of residual sera was tested for anti-VZV IgG by ELISA. We estimated age-specific seropositivity to VZV, controlling for sex and geographical distribution. We assessed differences between the proportions using the chi-square test and multivariable logistic regression. Seroprevalence data were compared to the varicella and herpes zoster-associated consultation rates in patients attending primary healthcare. RESULTS: Although 73.2 % (n = 1,540) of all samples were positive for VZV, only 11.2 % of samples collected from 1-year-olds were seropositive. There was a sharp increase in the proportion of seropositive in 3- and 5-year-olds (40.2 % and 65.4 %, respectively). By the school entry age of 6 years, 69.8 % of children were seropositive. The age-specific annual consultation rate for varicella in primary healthcare peaked in 1-year-olds, with 2,627 cases per 100,000 population. The profile of varicella-related consultations in primary healthcare mirrored the VZV seropositivity profile. The herpes zoster-related consultations in primary healthcare peaked in people over 70 years of age (702 cases per 100,000 population). CONCLUSIONS: VZV seroprevalence in Norway was somewhat lower than in some other European countries. The age-specific varicella-related consultation rates in primary healthcare mirrored the age profile of VZV seroprevalence.

Incidencia de la varicela y el herpes zóster antes de la introducción de la vacunación sistemática infantil en Navarra, 2005-2006 / Varicella and herpes zoster incidence prior to the introduction of systematic child vaccination in Navarre, 2005-2006

La varicela es una enfermedad aguda muy contagiosa producida por el virus varicela-zoster, que deja inmunidad duradera. El herpes zóster se produce por reactivación de una infección latente por el mismo virus. La introducción de la vacunación sistemática y gratuita frente a la varicela en niños de 15 meses de Navarra desde 2007, previsiblemente producirá cambios epidemiológicos importantes. Por ello, describimos la situación epidemiológica previa, en el periodo 2005-2006.Se han analizado los casos de varicela y herpes zóster registrados en las historias clínicas informatizadas de atención primaria, en la base de datos de altas hospitalarias (CMBD) y en el registro de mortalidad. Entre 2005 y 2006 se diagnosticaron 9908 casos de varicela (8,29 anuales por 1000 habitantes), siendo el 90% en menores de 15 años. Hubo 80 ingresos (8 por cada 1000 casos), complicaciones en 2,5 de cada 1.000 casos y se produjo un fallecimiento por esta causa (0,1 por 1000 casos). En el mismo periodo se diagnosticaron 4.959 casos de herpes zóster (4,15 casos anuales por 1.000 habitantes), la mitad en mayores de 55 años. Hubo 179 ingresos (36 por 1.000 casos), cuya edad media fue de77 años, y 83 presentaron complicaciones (16,7 por 1.000 casos). Este patrón epidemiológico es similar al encontrado en otros lugares antes de la introducción de la vacuna (AU)

Varicella is an acute and highly contagious disease produced by the varicella-zoster virus, which leaves lasting immunity. Herpes zoster is produced by reactivation of a latent infection of the same virus. The introduction of systematic and free vaccination against varicella in children of 15 months in Navarre from 2007 onwards can be expected to produce important epidemiological changes. For this reason we describe the previous epidemiological situation in the period from 2005 to 2006.We analysed all cases of varicella and herpes zoster registered in the electronic clinical files of primary care, in the database of hospital discharges and in the mortality register. Between 2005 and 2006, 9,908 cases of varicella were diagnosed (8.29 annually per 1,000 in habitants), with 90% in children under 15 years old. There were 80 hospital admissions (8 for every 1,000 cases), complications in 2.5 out of every 1,000 cases, and there was one death due to this cause (0.1 per 1,000 cases). In the same period, 4,959 cases of herpes zoster were diagnosed (4.15 cases per 1,000 in habitants), half in people over 55 years old. There were 179 hospital admissions (36 per 1,000 cases), whose average age was 77, and 83 presented complications (16.7 per 1,000 cases).This epidemiological pattern is similar to that found in other places before the introduction of the vaccine (AU)

Prevention of varicella: recommendations of the Advisory Committee on Immunization Practices (ACIP).

Two live, attenuated varicella zoster virus-containing vaccines are available in the United States for prevention of varicella: 1) a single-antigen varicella vaccine (VARIVAX, Merck & Co., Inc., Whitehouse Station, New Jersey), which was licensed in the United States in 1995 for use among healthy children aged > or = 12 months, adolescents, and adults; and 2) a combination measles, mumps, rubella, and varicella vaccine (ProQuad, Merck & Co., Inc., Whitehouse Station, New Jersey), which was licensed in the United States in 2005 for use among healthy children aged 12 months-12 years. Initial Advisory Committee on Immunization Practices (ACIP) recommendations for prevention of varicella issued in 1995 (CDC. Prevention of varicella: recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 1996;45 [No. RR-11]) included routine vaccination of children aged 12-18 months, catch-up vaccination of susceptible children aged 19 months-12 years, and vaccination of susceptible persons who have close contact with persons at high risk for serious complications (e.g., health-care personnel and family contacts of immunocompromised persons). One dose of vaccine was recommended for children aged 12 months-12 years and 2 doses, 4-8 weeks apart, for persons aged > or = 13 years. In 1999, ACIP updated the recommendations (CDC. Prevention of varicella: updated recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 1999;48 [No. RR-6]) to include establishing child care and school entry requirements, use of the vaccine following exposure and for outbreak control, use of the vaccine for certain children infected with human immunodeficiency virus, and vaccination of adolescents and adults at high risk for exposure or transmission. In June 2005 and June 2006, ACIP adopted new recommendations regarding the use of live, attenuated varicella vaccines for prevention of varicella. This report revises, updates, and replaces the 1996 and 1999 ACIP statements for prevention of varicella. The new recommendations include 1) implementation of a routine 2-dose varicella vaccination program for children, with the first dose administered at age 12-15 months and the second dose at age 4-6 years; 2) a second dose catch-up varicella vaccination for children, adolescents, and adults who previously had received 1 dose; 3) routine vaccination of all healthy persons aged > or = 13 years without evidence of immunity; 4) prenatal assessment and postpartum vaccination; 5) expanding the use of the varicella vaccine for HIV-infected children with age-specific CD4+ T lymphocyte percentages of 15%-24% and adolescents and adults with CD4+ T lymphocyte counts > or = 200 cells/microL; and 6) establishing middle school, high school, and college entry vaccination requirements. ACIP also approved criteria for evidence of immunity to varicella.

Immediate and longer term impact of the varicella shortage on children 18 and 24 months of age in a community population.

BACKGROUND: Little is known about the impact of the recent varicella vaccine shortage. To assess the temporal trend in varicella vaccine administration before 18 and 24 months of age in a community cohort of children prior to, during and after the recent varicella vaccine shortage. And to compare the temporal trends in varicella vaccinations to trends of an older, more widely accepted vaccine, the MMR. METHODS: Community population-based birth cohorts were identified who were eligible for the varicella vaccination before, during and after the 2001 to 2002 varicella vaccine shortage. Only children (84% of all) who remained in the community through their second birthday were included. For each child in the cohort, the medical records and immunization registry records from both medical facilities in the county were reviewed to identify the dates and sites for all varicella immunizations given. In addition to varicella immunizations, the dates of all MMR vaccinations were recorded. Additional data abstracted included the child's birth date, gender and dates of any recognized cases of chickenpox up through age 24 months. RESULTS: Of the 2,512 children in the birth cohorts, 50.8% were boys. In the three cohorts combined, 81.1% of the boys and 79.3% of the girls (p = 0.30) received the varicella vaccine by age 24 months. The pre-shortage community rate of varicella immunization was 79.7% by 24 months of age. During the varicella vaccine shortage, the rate of varicella immunization by 24 months fell to 77.2%. Only 6 additional children received a "catch-up" immunization by 36 months of age. In the post shortage period the community 24-month immunization rate rebounded to a level higher than the pre-shortage rate 84.0%. During the almost three years of observation, the MMR immunization rate by age 24 months was constant (87%). CONCLUSION: The varicella shortage was associated with an immediate drop in the 24-month varicella immunizations rate but rebounded quickly to above pre-shortage rates. In this community the only long term impact of the varicella vaccine shortage may be on the small number of children who still had not received catch-up varicella immunizations by 36 months of age.

Increasing evidence of immunity to varicella among children in Massachusetts, 1999-2003.

BACKGROUND: Experiences with vaccine-preventable diseases have demonstrated the success of school-entry requirements in increasing vaccination coverage and decreasing disease incidence. This study examines the effect of early implementation of daycare and school-entry requirements for varicella vaccination on recorded varicella immunity of preschool and school-aged children in Massachusetts. METHODS: Immunization surveys were conducted in licensed child care centers and schools with kindergarten and/or 7th grades. Evidence of immunity to varicella was defined as having physician verified records of varicella vaccination or disease history from the 1999-2000 through 2003-2004 school years. RESULTS: During the 5-year study period, physician-certified reliable history of varicella disease decreased in each grade level while vaccination coverage increased. The increase in the number of children in each grade level receiving varicella vaccine led to an increase in the overall percentage of children with evidence of immunity to varicella: 85% to 97% for children aged 2 years or more in child care, 93% to 98% for children in kindergarten, and 88% to 92% for children in 7th grade. CONCLUSIONS: The implementation of daycare and school-entry requirements for varicella vaccination within 4 years of the start of the varicella vaccination program in Massachusetts was associated with high levels of vaccination coverage in the cohorts of children targeted by the requirements. Although evidence of immunity from varicella disease decreased during the study period, the increase in varicella vaccination coverage compensated for the decline in disease history, resulting in a higher proportion of young children with evidence of immunity to varicella.

The incidence of varicella and herpes zoster in Massachusetts as measured by the Behavioral Risk Factor Surveillance System (BRFSS) during a period of increasing varicella vaccine coverage, 1998-2003.

BACKGROUND: The authors sought to monitor the impact of widespread varicella vaccination on the epidemiology of varicella and herpes zoster. While varicella incidence would be expected to decrease, mathematical models predict an initial increase in herpes zoster incidence if re-exposure to varicella protects against reactivation of the varicella zoster virus. METHODS: In 1998-2003, as varicella vaccine uptake increased, incidence of varicella and herpes zoster in Massachusetts was monitored using the random-digit-dial Behavioral Risk Factor Surveillance System. RESULTS: Between 1998 and 2003, varicella incidence declined from 16.5/1,000 to 3.5/1,000 (79%) overall with > or = 66% decreases for all age groups except adults (27% decrease). Age-standardized estimates of overall herpes zoster occurrence increased from 2.77/1,000 to 5.25/1,000 (90%) in the period 1999-2003, and the trend in both crude and adjusted rates was highly significant (p < 0.001). Annual age-specific rates were somewhat unstable, but all increased, and the trend was significant for the 25-44 year and 65+ year age groups. CONCLUSION: As varicella vaccine coverage in children increased, the incidence of varicella decreased and the occurrence of herpes zoster increased. If the observed increase in herpes zoster incidence is real, widespread vaccination of children is only one of several possible explanations. Further studies are needed to understand secular trends in herpes zoster before and after use of varicella vaccine in the United States and other countries.

The 2002 United States varicella vaccine shortage and physician recommendations for vaccination.

BACKGROUND: The US experienced a shortage of varicella vaccine in 2002, leading to the concerns about its impact. METHODS: 204 Minnesota and Pennsylvania physicians, most (164) of whom were interviewed in 1999 on the topic of varicella vaccine, responded to a 2003 survey. RESULTS: Although 67% were aware of the 2002 varicella vaccine shortage, 24% experienced it and only 45% were aware of the 2002 temporary change in national vaccination recommendations. In response, more vaccinated until the supply was exhausted (59%) than postponed vaccination as recommended (41%). Most (91%) reported that the shortage did not change their likelihood of recommending vaccine. From 1999 to 2003, the percentage of physicians highly likely to recommend vaccination increased from 73% to 82% for children 12-18 months old (P < 0.01). In 2003, more physicians believed that it was likely for secondary skin infections to occur following varicella disease and for parents to request vaccination than in 1999 (P < 0.01). Almost all (93%) physicians in both years believed that serious side effects were unlikely. CONCLUSIONS: Over half of physicians were unaware of the change in vaccine recommendations due to the shortage and many did not follow that change, suggesting the need for a different strategy.

Varicella zoster virus vaccination policies and surveillance strategies in Europe.

The incorporation of varicella zoster virus (ZVV) vaccination in childhood immunisation schedules is becoming an increasingly common option in Europe. The current study forms part of the European Sero-Epidemiology Network 2 (ESEN2) organisational analysis for VZV and describes current passive immunisation policies, as well as current and proposed active immunisation strategies, and existing surveillance systems for diseases caused by the varicella zoster virus in ESEN countries. A questionnaire was compiled and distributed to 23 participating countries. A VZV vaccine is currently licensed in 14 of the 20 participating ESEN countries. Germany is the only country to have incorporated VZV vaccination into its routine childhood immunisation programme. Three further countries currently recommend vaccination of children against VZV and five countries are also considering introducing routine immunisation against VZV for children. However, of the eight countries with or considering introducing childhood VZV immunisation, only six have case-based mandatory notification of varicella, and only two countries have primary care surveillance data available for herpes zoster.

Varicella epidemiology and cost-effectiveness analysis of universal varicella vaccination program in Taiwan.

Varicella zoster virus is highly contagious and affects people worldwide. In this study, we collected local epidemiological data and evaluated the cost-effectiveness of varicella vaccination program in Taiwan. To examine the economical consequences of universal vaccination, a model of the incidence and the associated costs in a hypothetical cohort was created each year for 30 years. The incidence increased sharply after the infancy and peaked in children aged 5 years. The hospitalization rate among cases was the highest in infants, followed by adults 30 to 44 years old. The benefit-cost analysis showed that one dollar invested in the program would cost extra 46 cents in direct medical expense, but would save extra 45 cents considering the societal expenses. Substantial economical benefits can occur due to the averted unproductive days for parents. Sensitive surveillance of both varicella and zoster is essential in countries that have implemented or are about to implement varicella vaccination.

Situación general y problemática de la varicela en España / No disponible

Se presenta un análisis epidemiológico de la varicela en España en los últimos años. Según el sistema de Enfermedades de Declaración Obligatoria (EDO) y la Red Nacional de Vigilancia Epidemiológica (RENAVE) la incidencia anual media de casos entre 1980 y 2000 es de aproximadamente 300.000. La mayoría se acumulan entre mayo y julio, describiéndose ciclos epidémicos cada 2 o 3 años. Según el último Conjunto Mínimo Básico de Datos (CMBD) de 1998, en este año se recogen 1.469 diagnósticos de varicela que requieren hospitalización (55,9 % varones y 44,1 % mujeres). La estancia media fue de 7 días. Las complicaciones más frecuentes fueron la neumonía hemorrágica en 246 casos y la encefalitis posvaricela en 55. La neumonía hemorrágica ocurrió en cerca del 80 % de los casos en mayores de 15 años y la encefalitis en el 22 % de los mayores de esta edad. La mayoría de casos ingresados corresponden a los menores de 5 años y a los de 25 a 34, siendo el porcentaje de casos complicados parecidos en ambos grupos de edad. En 1998 hubo 2 muertes en mujeres de 36 y 31 años, ambas con neumonía hemorrágica y dependencia tabáquica. Entre los años 1981 y 1997 se produjeron entre 3 y 6 defunciones por año. La encuesta de seroprevalencia de 1996 evidenció seropositividad en el 50 % de los niños de 2 a 5 años y en el 90-100 % de los de 15 a 19. Se hace notar que la cobertura vacunal mayor del 90 % hará que el impacto de la varicela disminuya en niños y adultos (AU)

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Farmacovigilancia de la vacunación antivaricela / No disponible

Dentro de los diferentes trabajos realizados en esta monografía sobre la vacuna de la varicela, nos ha correspondido revisar el tema de la farmacovigilancia de la vacuna, estudiaremos en qué consiste, qué objetivos persigue y con qué medios contamos para valorar este concepto. Qué es la reactogenicidad de la vacuna, qué son las reacciones adversas provocadas por las vacunas, cuáles pueden encontrarse tras la vacunación de la varicela y en cuántas ocasiones estas posibles reacciones adversas se han podido relacionar directamente con la administración de ésta. Para conocer en qué consiste la seguridad de la vacuna, revisaremos los principales estudios llevados a cabo sobre la misma, artículos en donde se analizan estos aspectos, desde los trabajos realizados durante los períodos prelicenciación de la vacuna para su comercialización (estudios precomercialización) hasta los realizados una vez que la vacuna se administra de forma sistemática o de forma parcial, a grupos de pacientes autorizados (estudios poscomercialización), estudios que en la actualidad ya cuentan con más de 20 años de experiencia (AU)

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Indicaciones actuales de la vacuna antivaricela / No disponible

En la inmensa mayoría de los casos la varicela tiene un curso benigno, pero dada su enorme morbilidad (del 90 al 95 % de la población), la asistencia sanitaria que requiere y las ausencias escolares y laborales que origina significan una importante carga social y económica. Por otra parte, los casos graves de varicela (encefalitis, síndrome de Reye, sobreinfecciones bacterianas graves de la piel, formas progresivas con diseminación visceral), proporcionalmente muy pocos, no dejan de ser responsables de cierto número de fallecimientos (de 5 a 6 anuales en España) y secuelas graves permanentes. Estos datos son suficientes para propugnar un uso generalizado de la vacuna antivaricela y su inclusión en el calendario vacunal universal. Por el momento, esto sólo se da en determinados países, pero en España todavía no. La vacuna está disponible en nuestro país pero es una especialidad de "Diagnóstico Hospitalario" indicada para adolescentes y adultos seronegativos así como grupos de población con riesgo de padecer una forma grave de varicela tales como: a) niños con leucemia linfoblástica aguda que reúnan determinadas condiciones; b) niños con tumores sólidos; c) niños con enfermedades crónicas; d) niños en programa de trasplante, y e) niños con enfermedad cutánea diseminada y sus contactos sanos no inmunes. Estas indicaciones son unánimemente admitidas, pero es de desear su ampliación hasta incluir a todos los niños (AU)

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Varicela: una enfermedad prevenible. Conclusiones / No disponible

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