Who’s holding the baby? A prospective diary study of the contact patterns of mothers with an infant

Patricia Therese Campbell, Jodie McVernon, Niraj Shrestha, Paula M. Nathan, Nicholas Geard

Models of infectious disease are increasingly utilising empirical contact data to quantify the number of potentially infectious contacts between age groups. While a growing body of data is being collected on contact patterns across many populations, less attention has been paid to the social contacts of young infants. We collected information on the social contacts of primary carers of young infants and investigated their potential for use as a proxy for contacts made by their infant. We recruited primary carers of infants under one year of age residing in two geographically, demographically and socioeconomically distinct local government areas of Melbourne, Australia - Boroondara and Hume - including a sub-group of Turkish-speaking participants. Participants recorded their own contacts in a paper diary and noted whether their infant was present or absent. Information collected included times at an address; description of location; and details on people contacted at the location. Descriptive summary measures and distributions of contacts by location type, intensity, day of contact and by age are reported. Of the 226 participants recruited, 220 completed diaries were returned. Participant contact patterns were similar across all groups, with respect to the types of locations, intensity and day of contact, with some variation in the number of unique daily contacts. The infant was present at around 85% of locations at which the primary carer contacted other individuals. The majority of contacts occurring when the infant was present were in Own Home (32%), Retail and Hospitality (18%) and Transport (18%) settings. The mean daily number of unique contacts by infants was estimated as 9.1, 8.7 and 6.5 in Boroondara, Hume (English) and Hume (Turkish), respectively, with a similar age distribution across each of our surveyed groups. Our demonstration that contact patterns of mothers with infants are reasonably robust to socioeconomic and cultural differences is a step forward in modelling infectious disease transmission. With infants spending most of their time in the company of their mother, contact patterns of mothers are a useful proxy measure of infant contact patterns. The age distribution of contacts made by infants estimated in this study may be used to supplement population-wide contact information commonly used in infectious disease transmission models.