The number of deaths among infants under one year of age in England with pertussis: results of a capture/recapture analysis for the period 2001 to 2011

Pertussis activity in England in 2012 was at its highest level for more than 12 years, leading to an increased number of deaths, especially among infants who were too young to be vaccinated. To support decision making on the introduction of maternal immunisation as an outbreak response measure to prevent these early deaths, we analysed reported deaths amongst infants of less than one year of age during the period from 2001 to 2011 with a capture/recapture analysis. We used log linear regression to allow for interactions. Reported deaths were obtained from the Hospital Episode Statistics for England, death registered by the Office of National Statistics and the enhanced surveillance of laboratory-confirmed pertussis conducted by the Health Protection Agency. There were a total of 48 deaths recorded; of these 41 had a disease onset before being fully protected by vaccination. Around half of these deaths (23) were recorded in all three datasets and 10 in only one. Due to the high coverage of the datasets the estimated number of deaths missed was small with 1.6 (95% confidence interval (CI): 0.5-4.5) deaths. The total average incidence was 0.721 (95% CI: 0.705-0.763) per 100,000 maternities. We concluded that under ascertainment of deaths from diagnosed pertussis cases is small. .