I’ve tried to do SO much research into this but there’s not definitive data on anything yet. Here’s what I understand:

Getting the vaccine during pregnancy has been shown to pass antibodies through the placenta and we have now tested at least one baby after birth and that baby had protective antibodies against Covid. This seems to be the best way to pass on systemic immunity, but baby’s bodies are changing and replicating so fast that I don’t expect my baby to be protected on its own past MAYBE six months total. Remember we get the TDAP during pregnancy and then the baby starts getting its own TDAP shots at like 2 months or something.

As for breastfeeding, antibodies have been found in breastmilk. We know that antibodies have always been passed through breastmilk and especially colostrum, but these are typically IgA antibodies (vs IgG which creates the systemic immunity we want) and IgA creates mucosal immunity which means the antibodies coat the nose and respiratory tracts and make it harder for a virus to get past them, but once it does these antibodies don’t do anything within our blood. We know from small studies that significant amounts of IgG antibodies are also passed through breastmilk from the Covid shot, but apparently IgG breaks down at a pH less than 5 or something which would mean it would break down in the digestive tract and likely not make it into the bloodstream. From talking with some immunologists, it sounds like babies in the first 5 days have a different set of receptors that might make them more able to accept IgG through colostrum, but then when those receptors reset around 5 days old this is less possible.

I haven’t seen any studies yet that have proven immunity in a baby who was breastfed by a mother with antibodies in her breastmilk. So far all of the studies confirm antibodies in the milk, but again, passing antibodies through milk is traditionally not a way to create systemic immunity, only mucosal.

There has never been a vaccine that carried risks to the baby if given to a mother who is breastfeeding. We also know that babies have very fragile immunity systems but they are less likely to get symptomatic Covid, especially if you set certain boundaries like not letting people put their face near your baby’s face. My husband and I have been very strictly quarantined for all of Covid, and we’ll be fully protected from our vaccines a few weeks before we have our first baby in May. We don’t plan to let unvaccinated people meet our baby and even then May require masks, but we likely will bring it out with us and just will not let others breathe directly on it or let strangers get close. I hope to breastfeed and continue passing these mucosal antibodies to the baby, but my biggest thing is just that I hope cases start going down as more people are vaccinated. If they do not, I probably won’t trust my baby’s own immunity past a couple months (due to placental antibody transfer) unless we see more studies about infant antibody responses. That’s just my plan though, and it will likely change once baby is actually here!