HONG KONG - Babies born to mothers who have recovered from COVID-19 infection have antibodies against the virus, according to a study of the Chinese University of Hong Kong on Friday.

The Department of Obstetrics and Gynaecology of the university's Faculty of Medicine recruited pregnant women from local public hospitals with infection of SARS-CoV-2, the virus that causes COVID-19, between March 2020 and January 2021, and analyzed data from 20 subjects who had delivered their babies by Jan. 31, 2021.

The results showed that 12 of 13 neonates born to mothers with recovered infection tested positive for anti-SARS-CoV-2 Immunoglobulin G (IgG), confirming the mother-to-child transfer of anti-SARS-CoV-2 antibodies.

The study also found that a negative relationship was observed between IgG concentration in cord and maternal sera with infection-to-delivery interval, meaning the longer the interval the lower the IgG concentrations. There was a significant negative relationship between the transplacental IgG transfer ratio with viral load.

Liona Poon, the key investigator of the study and professor from the Department of Obstetrics and Gynaecology of the university, said that the findings raised the question of the potential impact of vaccine-induced immune response on mother-to-baby transfer of anti-SARS-CoV-2 IgG.

"There is an urgent need to generate clinical data on efficacy and safety of the various COVID-19 vaccines in pregnant women as well as to determine the vaccine technology and timing of vaccination which can best deliver maximum potential benefits to pregnant women and their babies," she added.

The study has been published in an international journal Ultrasound in Obstetrics and Gynecology.