Impact of the US Two-dose Varicella Vaccination Program on the Epidemiology of Varicella Outbreaks

Abstract

Background A routine 2-dose varicella vaccination program was adopted in 2007 in the United States to help further decrease varicella disease and prevent varicella outbreaks. We describe trends and characteristics of varicella outbreaks reported to CDC during 2005–2012 from 9 states. Methods Data on varicella outbreaks collected by 9 state health departments were submitted to CDC using the CDC outbreak reporting worksheet. Information was collected on dates of the outbreak, outbreak setting, and number of cases by outbreak; aggregate data was provided on the numbers of outbreak-related cases by age group, vaccination status, and laboratory confirmation. Results Nine hundred and twenty-nine outbreaks were reported from the 6 states which provided data for each year during 2005–2012. Based on data from these 6 states, the number of outbreaks declined by 78%, decreasing from 147 in 2005 to 33 outbreaks in 2012 (p=0.0001). There were a total of 1,015 varicella outbreaks involving 13,595 cases reported by the 9 states from 2005–2012. The size and duration of outbreaks declined significantly over time (p<0.001). The median size of outbreaks was 12, 9, and 7 cases and median duration of outbreaks was 38, 35, and 26 days during 2005–2006, 2007–2009, and 2010–2012 respectively. Majority of outbreaks (95%) were reported from schools, declining from 97% in 2005–2006 to 89% in 2010–2012. Sixty-five percent of outbreak-related cases occurred among 5–9 year olds, with the proportion declining from 76% in 2005–2006 to 45% during 2010–2012. Conclusions The routine 2-dose varicella vaccination program appears to have significantly reduced the number, size, and duration of varicella outbreaks in the U.S.

Varicella outbreak trends in school settings during the voluntary single-dose vaccine era from 2006 to 2017 in Shanghai, China

“…This study found that the proportion of BV cases among all outbreak-related cases was 56.5%, higher than the results of a population-based survey (22%) (Chaves et al, 2008), but within the range of several outbreak-based studies (42-76%) (Leung et al, 2015;Zhang et al, 2014b;Zhu et al, 2017). It was also found that the proportion of BV cases showed an increasing trend from 30.4% in 2008 to 85.7% in 2017.…”

“…The results of a meta-analysis also showed that VE against all varicella increased significantly from 81% in the single-dose VarV era to 92% in the two-dose VarV era (Marin et al, 2016). In addition, monitoring data showed that the numbers, size, and duration of varicella outbreaks in the USA have decreased significantly since the implementation of a routine two-dose VarV program (Leung et al, 2015). Fortunately, a voluntary two-dose VarV schedule has been recommended in Shanghai, China, since November of 2017 (Shanghai Municipal Health and Family Planning Commission, 2017) and was included in the immunization program of Shanghai in August 2018 ( Figure 1).…”

Seroepidemiology of varicella in Hangzhou, China in the vaccine era

“…20 Study on epidemiology of varicella during the 2-dose VarV Program in the United States shows that between the period 2005-2006 (before the 2-dose recommendation) and 2013-2014, overall varicella incidence declined 84.6%, with the largest declines reported in children aged 5-9 years (89.3%) and 10-14 years (84.8%). 21 The routine 2-dose varicella vaccination program appears to have significantly reduced the number, size and duration of varicella outbreaks in the US 22 A 2nd dose may deserve additional consideration to control varicella outbreak and for development of an adequate and persisting antibody response. 23 In conclusion, in order to prevent varicella transmission and outbreaks, 2 doses of secondary VarV immunization are preferred.…”

Epidemiology of Varicella During the 2-Dose Varicella Vaccination Program — United States, 2005–2014

“…Previous reports have documented significant declines in varicella incidence in the United States since the varicella vaccination program was implemented in 1996 through the early years of the 2-dose program (1,(3)(4)(5)(6)(7)(8). During 1995-2010, data to assess impact of the varicella vaccination program were obtained from a varicella active surveillance project, which was discontinued in 2010 (3).…”