Social contact patterns of infants in deciding vaccination strategy: a prospective, cross-sectional, single-centre study

Abstract

Social contact between individuals is believed to be a fundamental cause in the transmission of many respiratory tract infections. Because they have not yet been fully vaccinated, infants are at high risk for contracting whooping cough, influenza and their serious complications. Therefore, determining infant social contact patterns is an important step in protecting them from respiratory tract infection. This study included 1200 healthy infants (<12 months of age). Social contact diaries were used to estimate the frequency and nature of the infants' social contacts. This survey also gathered information regarding the infants' respiratory symptoms and their frequency of attendance at crowded places over a period of 1 week. The diary return rate was 83.8% (N = 1006), and there was a total of 4706 contacts reported for these infants. The median daily contact number per capita was 4 (range 1-18). The median number of contacts with adolescents was 0 (range 0-7). Of the infants, 50.3% had contact with non-household individuals. The mothers had the longest contacts with their babies. Contacts with school children, frequency of attendance at crowded places and age were determined to be significant effective factors for reporting respiratory symptoms. Results suggest that school-age siblings and the mothers should be primarily vaccinated, and parents should keep their babies away from crowded places for protecting their infants.

Infant contact in day-care centres in Vietnam: A cross-sectional study to understand infant infection risk

“…Contacts with other children mostly lasted only for a few minutes, and those with childcare personnel lasted longer (greater than five minutes in duration). Similarly, studies of infants outside of the day-care setting found most contacts to be regular 8 ; however, those contacts usually lasted over multiple hours (Kovacs, personal communications, 7, 8 ). This may be in part due to the difference in the definition of contact in this study and those in the previous studies 7, 8 .…”

“…The average number of contacts with different individuals was 6.9 (SD 3.2) during the infants’ stay at day-care on the day of observation. Previous studies have found the average number of contacts of an infant per day outside of day-care to range from 4.3 (Kovacs, personal communications) to 4.6 7 or to 6.68 8 . However, these studies collected contact information by asking the mother/guardian to record all the contacts in one day.…”

“…Trained field workers from Khanh Hoa Health Service (KHHS) observed and recorded the physical (skin-to-skin) contacts of each infant for one day at the day-care centre (from arriving to leaving) using a contact record form which was developed in line with previously conducted contact surveys (see extended data: Form 1 13 ) 4, 7, 8 . First, the observers chronologically noted each physical contact with the name of the contact person and the precisely measured time of the contact.…”

“…Assuming a mean of 5 contacts per infant based on previous studies which recorded mean number of contacts in a day as 4.3 to 6.68 (Kovacs, personal communications; 7, 8 ) and that the number of contacts follows a t-distribution, a precision of +/-1.5 contacts at the 95% confidence level was expected to be obtained by enrolling at least 10 infants. Hence, we targeted 10 to 30 infants, 1 to 3 infants from each of 10 day-care centres, for this study.…”

“…Several age-stratified contact studies have been performed 4– 6 , yet the contact patterns of infants remain poorly described, not only because we cannot ask them directly but also because mothers do not have an overview of their contact during a whole day when they are in day-care 7, 8 . A study in the UK 8 , one in Turkey 7 , and another in Nha Trang, 2017 (Kovacs, personal communication) investigated contact patterns focusing on infants by asking the mother/guardian to record all the contacts in one day. However, their methods were not effective to capture the actual contact behaviour in the day-care setting because mothers/guardians often do not know what occurs daily in that setting.…”