One standout observation regarding the clinical epidemiology in the
current COVID-19 pandemic is the relatively low incidence and generally
mild presentation of the infections in children (Ludvigsson, 2020).
Indeed, only 230 pediatric cases with 3 neonates have been reported in
China through February 6 2020 (Lu & Shi, 2020) with a total of only 9
infected and hospitalized cases identified between December 8 2019 and
February 6 2020 out of a total of 31,211 cases of COVID-19 reported (Wei
et al., 2020). Moreover the course in infants and children was mild with
infection rarely progressing to lower respiratory tract infections (Hong
et al., 2020), and no deaths have been reported in this age group (Lu &
Shi, 2020).
Since SARS-CoV-2 is highly contagious, it is anomalous that the
infection rate is so low in infants and children given the high risk of
inevitable close contact they have with adults. So far, several theories
to explain this anomaly include lack of nicotine exposure in children,
and reduced expression of ACE2 cell surface receptors needed by
SARS-CoV-2 to gain entry to host at younger ages (Song et al., 2012).
Here we postulate another possibility for lower incidence and milder
disease is high lactoferrin content in breast or some infant formula
feedings.
Lactoferrin (Lf), which is highly concentrated in human milk as well as
often added to modern infant formulas has demonstrable broad-range
antiviral properties (Wakabayashi et al., 2014) including against
SARS-CoV, which uses the same ACE2 surface receptor to invade hosts as
SARS-CoV2 (Lang et al., 2011), thus, it is not inconceivable that
nutritional lactoferrin in breast milk or infant formula contributed to
reduced incidence as well as milder course of COVID-19 in infants and
young children. This intriguing possibility can be assessed by carefully
noting the feeding history of pediatric COVID-19 cases.
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