In this observational study, infants who received multidrug therapy before 6 months of age did not have the early-onset severe form of childhood HIV disease. Further studies are needed to find accurate early markers of disease progression in this age group.

Background The extent to which very young children contribute to the transmission of SARS-CoV-2 is unclear. We aimed to estimate the seroprevalence of antibodies against SARS-CoV-2 in daycare centres that remained open for key workers' children during a nationwide lockdown in France. Methods Children and staff who attended one of 22 daycare centres during a nationwide lockdown in France (between March 15 and May 9, 2020) were included in this cross-sectional, multicentre, seroprevalence study. Hospital staff not occupationally exposed to patients with COVID-19, or to children, were enrolled in a comparator group. The primary outcome was SARS-CoV-2 seroprevalence in children, daycare centre staff, and the comparator group. The presence of antibodies against SARS-CoV-2 in capillary whole blood was measured with a rapid chromatographic immunoassay. We computed raw prevalence as the percentage of individuals with a positive IgG or IgM test, and used Bayesian smoothing to account for imperfect sensitivity and specificity of the assay. This study is registered with ClinicalTrials.gov, NCT04413968. Findings Between June 4 and July 3, 2020, we enrolled 327 children (mean age 1•9 [SD 0•9] years; range 5 months to 4•4 years), 197 daycare centre staff (mean age 40 [12] years), and 164 adults in the comparator group (42 [12] years). Positive serological tests were observed for 14 children (raw seroprevalence 4•3%; 95% CI 2•6-7•1) and 14 daycare centre staff (7•7%; 4•2-11•6). After accounting for imperfect sensitivity and specificity of the assay, we estimated that 3•7% (95% credible interval [95% CrI] 1•3-6•8) of the children and 6•8% (3•2-11•5) of daycare centre staff had SARS-CoV-2 infection. The comparator group fared similarly to the daycare centre staff; nine participants had a positive serological test (raw seroprevalence 5•5%; 95% CI 2•9-10•1), leading to a seroprevalence of 5•0% (95% CrI 1•6-9•8) after accounting for assay characteristics. An exploratory analysis suggested that seropositive children were more likely than seronegative children to have been exposed to an adult household member with laboratory-confirmed COVID-19 (six [43%] of 14 vs 19 [6%] of 307; relative risk 7•1 [95% CI 2•2-22•4]). Interpretation According to serological test results, the proportion of young children in our sample with SARS-CoV-2 infection was low. Intrafamily transmission seemed more plausible than transmission within daycare centres. Further epidemiological studies are needed to confirm this exploratory hypothesis.

Perinatal thrombosis in infants born to mothers with antiphospholipid antibodies (aPL) is a rare event, but with risk of death or severe sequelae. We analysed 16 infants with such perinatal thrombosis reported in the literature in the last 20 years. Thromboses were arterial (13/16), mostly strokes (8/16). Hydrops fetalis with left renal vein thrombosis was associated to a lupus anticoagulant (LA) present only in the child. Risk factors additional to aPL: either prenatal (preeclampsia and/or intra-uterine growth retardation) or perinatal (asphyxia, sepsis, arterial or venous catheter and congenital thrombophilia) were present (one to four of them) in nine out of the 14 evaluable babies. aPL were the only risk factor found in five full term babies who suffered from stroke in four cases and from renal thrombosis in another. Eleven of these infants with aPL in their serum presented a neonatal APS with the same antibody (LA or aCL IgG) found in neonates and their mothers, while the other infants had thrombosis with aPL only in their mother's blood. aCL IgM was only found in one neonate who suffered from sepsis. Thrombosis treatments were diverse. This analysis suggests that women with aPL should be investigated for other thrombophilic risk factors and that aPL should be detected systematically at birth in the offspring of mothers with APS.