Future program evaluations may require rapid assessments of large samples of low incidence populations in order to measure targeted interventions. A case in point is the national effort to increase influenza vaccination among pregnant women to protect the health of the mother and the unborn child. The peak vaccination period for each influenza season is only about 3 months in length and less than two percent of adult women will be pregnant during this period. Hence, it is impractical to recruit and interview an effective sample of pregnant women during influenza season using traditional survey approaches, such as RDD telephone surveys. In order to assess the vaccination uptake and evaluate the knowledge, attitudes, and behaviors of pregnant women toward influenza vaccination during the 2010-11 influenza season, the CDC adopted an innovative non-probability approach to obtaining a large national sample of pregnant women during influenza season. A large national web panel was used to recruit adult women who were either currently pregnant or had been pregnant since the beginning of vaccination in August 2010 for the influenza season. The fall 2010 assessment was launched in November for an early estimate of vaccination during the peak activity of the vaccination period. Women currently or recently pregnant were recruited from the web panel, using both e-mail invitations to panelists (nearly 200,000) and website intercepts (nearly 30,000). In less than three weeks, we were able to interview a national sample of 1,500 eligible women, including minority oversamples. The demographic characteristics of the achieved sample were representative of population estimates. Moreover, the key variable, vaccination uptake, was consistent with estimates based on a small sample of currently pregnant women from the December 2010 BRFSS. This paper explores the methods and outcomes of this innovative method for rapid surveys of low incidence populations.