In order to understand this question, the following two questions will be clarified:
- What does immunity against COVID-19 entail?
- Is immunity transmitted to the children of mothers who had been affected by COVID-19 during pregnancy?
1. What is immunity against COVID-19?
Short answer: while immunity against COVID-19 might occur by developing cell mediated immune responses and antibodies, it is currently unclear whether a one time infection and subsequent development of an immune response prevents a future reinfection with COVID-19.
As with other viral infections, immunity against COVID-19 can be developed by either contracting and surviving the disease or receiving a vaccination against it. Both stimulate the immune system to produce two types of immune response: cell mediated immune responses (involving cells known as T-cells) and secondly production of antibodies in the infected person. These responses may help to prevent future infection by the same strain of the SARS-CoV-2 virus. Currently there is no conclusive evidence regarding whether a one-time infection with or vaccination against COVID-19 will protect against a reinfection with COVID-19.
One reason for this is that while the development of cell mediated or antibody responses may protect against SARS-CoV-2  in the short term it is unclear how long this protection will last as the virus only appeared in the beginning of the year and thus one can not draw any conclusion on the long term immunity and mutation of COVID-19. Nor do we understand whether the cell-mediated or the antibody responses (or a combination of the two) are protective. These immune responses recognise specific molecular shapes on viral proteins. Mutations in viruses can change these shapes allowing the virus to ‘escape’ from the immune response developed against an earlier strain.
Additionally, research on the more widespread versions of the coronavirus family such as those associated with the common cold, suggest that not only do antibody concentrations drop significantly 6 months after infection , but reinfection with the same type of coronavirus frequently occurs within a one year period . While these findings can not be generalised to the novel SARS-CoV-2 virus, they do raise some uncertainty regarding long term immunity.
2. Is this immunity transmitted to the children of mothers who had been affected by COVID-19 during pregnancy?
Short answer: while there is evidence that antibodies may be transferred to newborns from infected mothers during pregnancy and through breastfeeding, we have no information about whether these provide immunity to the newborns.
One way mothers can help babies obtain immunity against COVID-19 is the transmission of antibodies to their infants without the baby contracting COVID-19. Antibodies made by a mother infected by SARS-CoV-2 can be transmitted to the baby in two ways. Some antibodies are transported across the placenta during the last few weeks of pregnancy. Antibodies are also carried in breast milk for the first few days after birth and are an important way a mother can transfer protection against certain diseases to their infant. So far little research has been done on the transmission of SARS-CoV-2 antibodies towards infants. A study by Zeng and colleagues  found antibodies – but no positive result for COVID-19 – in 6 babies born to mothers who were infected with SARS-CoV-2 during pregnancy. While antibodies are a potential component of the immunity against COVID-19, the mere presence does not provide evidence that these babies are protected against the virus. Professor Simon Clarke, professor at the University this finding should be regarded with caution: ‘Even if the antibodies were protective, and there is no evidence of that, any immunity would dwindle because the mother’s B-cells which produce the antibodies, are not transferred.’ . This implies that the infants do not possess the means to sustain the immunity as the antibodies – and their possible protective effect would eventually vanish. Overall, there is evidence that antibodies may be transferred to newborns from infected mothers during pregnancy and through breastfeeding, but we have no information about whether these provide immunity to the newborns.
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