Study sheds light on critical windows in pregnancy for COVID-19 vaccination

Scientists have found evidence of lower than expected transfer of protective antibodies against vel coronavirus via placenta from mors who are infected in third trimester, findings that shed light on critical windows in pregnancy that may be most desirable for vaccination.

According to researchers, including those from Massachusetts General Hospital (MGH) in US, findings may be explained by a process where carbohydrate molecules in body alter antibodies after y are produced. y explained that altered attachments of carbohydrates to coronavirus-specific antibodies -- a process called glycosylation -- may be to blame for reduced transfer from mor to fetus.

In study, published in journal Cell, scientists compared maternal antibodies against flu (influenza), whooping cough (pertussis), and vel coronavirus -- SARS-CoV-2 -- and how se antibodies transferred across placenta. y found that influenza- and pertussis-specific antibodies were actively transferred in a relatively rmal fashion.

In contrast, researchers said transfer of SARS-CoV-2-specific antibodies to baby was t only significantly reduced, but antibodies transferred were less functional than those against influenza. According to scientists, reduced transfer was only observed in third trimester infection. study found that carbohydrate attachments on SARS-CoV-2-specific antibodies in maternal blood were different than those seen on influenza- and pertussis-specific antibodies.

researchers believe this carbohydrate pattern may cause COVID-specific antibodies to be "stuck" in maternal circulation, rar than transferred across placenta via placental antibody receptors. However, scientists said some increases in total maternal antibodies induced by viral infection helped to partially overcome problem and facilitate transfer of some functional antibodies from mor to fetus.

A higher placental expression of a receptor which attracts carbohydrate pattern on SARS-CoV-2-specific antibodies also helped, study ted. Based on analysis, scientists said some of antibodies that transferred best were also most functional, activating immune system's natural killer cells that could help newborn fight virus if exposed. researchers believe findings have implications for design of new vaccine candidates against SARS-CoV-2 for pregnant women.

"Vaccine regimens able to drive high levels of COVID-specific antibodies with glycosylation patterns favoured by placenta for selective transfer to fetus may lead to better neonatal and infant protection," says study co-author Andrea Edlow, a maternal-fetal medicine specialist at Massachusetts General Hospital.

scientists said study results may point to critical windows in pregnancy that may be most desirable for vaccination to optimise protection for both mor and her infant.