This is a secondary analysis of COVID IB4221/20PI, an ongoing multicentric observational study of clinical and epidemiological features of children who present for care in one of thirteen participating pediatric ESs located in Majorca, Spain, during the late summer and autumn 2020 period of the COVID-19 pandemic.
This study was conducted in two University Hospitals, a District Hospital, nine healthcare centers for community Pediatrics, and a Private Hospital, where COVID-19 testing was conducted free of charge.
Study design and participants
The first aim of our study was to analyze the effect of exclusive formula feeding on the risk of testing positive for SARS-CoV-2. The secondary aim was to examine the relationship between breastfeeding type and symptoms or diagnosis of children attending ESs during the COVID-19 pandemic. Eligible participants were those younger than 14 years of age who presented to a participating ES for care and who were tested for SARS-CoV-2 because of suspected COVID-19, ambulatory care or scheduled hospital procedures on the 2nd and 16th of each month from August to December 2020. The SARS-CoV-2 test from nasopharyngeal swab specimens targeted RNA-dependent RNA polymerase (RdRP), Nucleocapsid (N), and Envelope (E) gene sequences.
At enrollment in the ES, regardless of SARS-CoV-2 test results, all children had the same information collected, including demographic, epidemiological and clinical data. A study team member completed the enrollment form using the participants medical records and through a caregiver interview. Data collected included calendar date and site of enrollment, recent travel, exposures, household conditions, age, sex, health information (e.g., infant feeding, past medical history, weight, height), onset of current illness (e.g., timing, symptoms), and laboratory investigations performed in the emergency services. Study team members asked specifically about fever, asthenia, pain, diarrhea or respiratory symptoms, as well as other new or worsening health problems, and recorded the discharge diagnoses. Any diagnoses of respiratory tract infection, including acute otitis media (AOM), was validated with clinical examination. Since heart conditions, cerebral palsy, and chronic diseases are associated with more severe COVID-19 and multi-organ involvement , past medical history has focused specially on these pre-existing comorbidities.
Percentiles of body mass index (BMI) were determined according to the Spanish Orbegozo Foundation growth charts . A child’s weight status was established as defined by the Centers of Disease Control : individuals who had BMI values below the 5th percentile were classified as underweight, healthy weight was defined as a BMI at or above the 5th percentile and below the 85th percentile, overweight was defined as a BMI at or above the 85th percentile and below the 95th percentile, and obesity was defined as a BMI at or above the 95th percentile.
Estimation of breastfeeding rate
The independent explanatory variable was any breastfeeding. A brief interviewer-administered question was used to collect quality data recalled about lactation: “Was [child] ever breastfed directly at the breast?” Answer options: Yes / No / Don’t know / Refused. This is the first modified question of the validated Brief Breastfeeding and Milk Expression Recall Survey .
At the time of study development, the wide variation of COVID-19 incidence rate in pediatric patients (1 -16%)  precluded a robust sample size estimate. Hence, we have opted for a convenience sample of children screened for COVID-19 at the ES of Majorca during 5 months of August–December 2020, of the COVID-19 pandemic.
Statistical analyses were performed with IBM SPSS v.23 statistical software. Categorical data were presented as percentages. Normally distributed variables were described by means ± standard deviations. Proportions were compared using the Pearson’s chi-squared or the Fisher’s exact tests. Differences between means were studied through the Student’s T test. A P value < 0.05 was considered statistically significant.
The study was approved by the Balearic Conjoint Health Research Ethics Review Board. There is no direct benefit of study participation. Weekly interim analysis allowed for real-time data sharing with regional policy makers. A research team member at each institution contacted in-person the guardian/caregiver/child to obtain written informed consent and assent, as appropriate.
Preregistration: Aspredicted Trials Registry number is #62721.