Abstract
Background
Nationwide varicella outbreak surveillance was instituted in 2015 to monitor impact of the 2007 2-dose varicella vaccination recommendation in the US. Sentinel surveillance for varicella outbreaks in school settings demonstrated feasibility of outbreak surveillance.
Methods
Beginning August 2015, through CDC’s Epidemiology Laboratory Capacity funding, health departments conducted surveillance for varicella outbreaks, defined as ≥5 varicella cases in a setting within at least 1 incubation period (21 days). Health department staff collected case-based data on: outbreak setting, age, vaccination status, number of varicella vaccine doses, number of lesions, laboratory testing results, and whether cases resulted in hospitalizations and/or had complications.
Results
During 8/1/2015–1/7/2017, 49 jurisdictions reported 89 outbreaks (1,030 cases); 35 (39%) outbreaks occurred in schools, 16 (18%) in daycares, 37 (42%) in other settings, and 1 unknown setting. Median size and duration of outbreaks was 7 cases (range, 5–257 cases) and 29 days (0–160 days), respectively. Of 921 outbreak-associated cases with information on both age and vaccination, 68% (624) were in children aged 1–9 years and 77% (713) in unvaccinated persons. Among vaccinated patients with information on number of doses, 62% (119/192) were 1-dose varicella vaccine recipients. Among patients with information on number of lesions, 54% (414/767) had ≥50 lesions, of whom 86% were unvaccinated. Of vaccinees, 78% (79/101) with 1-dose and 76% (44/58) with 2-doses had <50 lesions (P = 0.84). Three patients were hospitalized, all unvaccinated; an additional 10 had complications (6 unvaccinated, 1 2-dose vaccinee, 3 1-dose vaccinees). Varicella was laboratory confirmed in 77 (7%) cases.
Conclusion
Although varicella outbreaks continue to occur most often in school-aged children and among unvaccinated persons, they are small (median of 7). Vaccinated patients had more mild disease (<50 lesions) and no hospitalizations compared with unvaccinated patients. Number of lesions did not differ significantly among 1- vs. 2-dose vaccinees. Continued varicella outbreak surveillance is critical for monitoring the impact of the 2-dose vaccination policy for controlling outbreaks.
Disclosures
All authors: No reported disclosures.