Current best evidence for clinical care (more info)
Current evidence suggests that coronavirus disease 2019 (COVID-19), caused by severe respiratory syndrome coronavirus 2 (SARS-CoV-2), is predominantly transmitted from human-to-human. However, evidence on vertical transmission and natural passive immunity among the newborns exposed to COVID-19 is scanty and varies. This poses a challenge on preventive interventions for the newborns. We conducted a systematic review to first, determine the likelihood of vertical transmission among COVID-19 exposed infants and second, determine whether antibodies against SARS-CoV-2 were generated among COVID-19 vertically exposed but negative infants. This review registered in PROSPERO searched evidence from PubMed/MEDLINE and Google Scholar, among others. About 517 studies were pooled, where 33 articles (5.8%) met the inclusion criteria such as infection prevention and control measures at birth. A total of 205 infants born to COVID-19 positive mothers were studied. Overall, 6.3% (13/205; 95% CI: 3.0%-9.7%) of the infants tested positive for COVID-19 virus at birth. Of 33 eligible studies, six studies (18.8%) reported about immunoglobulin G/M (IgG/IgM) against SARS-CoV-2. IgG/IgM were detected in 90% infants (10/11; 95% CI: 73.9%-107.9%) who tested negative for COVID-19 virus. The median antibody levels detected were 75.49 AU/ml (range, 7.25-140.32 AU/ml) and 3.79 AU/ml (range, 0.16-45.83 AU/ml), p = .0041 for IgG and IgM, respectively. In conclusion, the current evidence revealed a low possibility of vertical transmission of COVID-19 and antibodies against SARS-CoV-2 were detected among vertically exposed but negative infants. Further studies on transplacental transmission and the magnitude of natural passive immunity in infants born to mothers with COVID-19 are warranted.
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These are basic science matters, which normally should not influence care. However, in absence of real outcomes, this might be the best evidence we have in the early stage of the pandemic until more is known.
It would have been helpful if the authors had better separated neonatal IgM versus IgG since IgM does not cross the placenta and its presence suggests possible neonatal infection rather than maternal antibody. They did briefly mention this in a single sentence.
Evidence on vertical transmission of the coronavirus needs to be further studied, considering the difficulty of studies that can prove this transmission. Immunity in newborns of pregnant women infected in the same way still needs to be better clarified, complementing whether the presence of antibodies against the virus at birth confers immunity and for how long. Despite this, this live systematic review, compiling 33 studies, brings very relevant information about the presence of IgG and IgM in most neonates.