Research Update: Breastfeeding and COVID-19 Vaccination

Below is a transcript of the video research update I recorded on the 1st September 2021 and loaded to my social media channels on 2nd Sept 2021 regarding breastfeeding and vaccination against COVID-19. As per the disclaimers made in the text below, this is for information purposes only and does not replace discussions with your medical team regarding your personal vaccination choices. If you wish to clarify your understanding of the information I've provided here or ask any questions you are welcome to do so via the contact form on the home page of this website, by email, or via DM on social media channels. 



Hello my name is Anna Cusack, I am an author, doula, podcaster, and parent support professional. I have uni post-graduate qualifications in Clinical Exercise Physiology specialising in rehabilitation and I also spent many years working as a health professional in community and hospital settings.

In this video I want to discuss breastfeeding and vaccination against COVID-19. The Royal Australian College of Obstetricians and Gynaecologists released a statement on the 18th August 2021 saying that vaccination is recommended for breastfeeding people, and that all of the three vaccines available here in Australia are considered safe, so Pfizer, Moderna or AstraZeneca (which is now being called Vaxzevria here because that’s the name that is used elsewhere in the world). This is inline with advice from the Australian Breastfeeding Association.

Despite this, many breastfeeding mothers and people who provide their babies human milk are concerned regarding getting vaccinated because of the unknown effects it could have on their babies, and are having difficulty accessing the statistics behind the recommendations these associations are making. The aim of this video is to present data from research studies so you can feel more confident discussing possible vaccination with you healthcare provider. It does not replace this conversation in any way and the choice is ultimately up to you. This video is being recorded on the 1st of September 2021 and new information may come to light as more studies are released, so I would encourage you to stay up to date with that, using the Google Scholar search engine is the easiest way for the majority of people to access the abstracts or summaries of research papers, and in many cases the full text of the articles are freely available as well.

So I’ve read through as many published, legitimate research studies as I could find on the topic of breastfeeding and COVID-19 vaccination, most if not all of which have been released since February this year. Where possible I’ve used peer-reviewed studies, so that means research that has been critiqued and reviewed by people who weren’t involved in running the study and are experts in their field. I won’t discuss all of these articles but I can assure you that I haven’t cherry-picked them, there were no articles in my reading that came to opposing conclusions that I have wilfully ignored according to my personal opinions or preferences, I am merely presenting a cross-section of the reputable data that is available.

So some background on this topic of lactation and COVID-19 vaccination to start with. The Australian product information leaflet for the Pfizer vaccine (also called the Comirnaty vaccine) notes that there were no issues in animal studies regarding lactation in the drug but that human data wasn’t available at the time of its publication on 25th January 2021.

The passage I’m about to read comes from the WHO document called the “Interim recommendations for use of the Pfizer–BioNTech COVID-19 vaccine, BNT162b2, under Emergency Use Listing”. This document was first released in 8th January 2021 and was updated on 15th June 2021.

“Lactating women: Breastfeeding offers substantial health benefits to lactating women and their breastfed children. Vaccine effectiveness is expected to be similar in lactating women as in other adults. Data are not available on the potential benefits or risks of the vaccine to breastfed children. However, as BNT162b2 is not a live virus vaccine and the mRNA does not enter the nucleus of the cell and is degraded quickly, it is biologically and clinically unlikely to pose a risk to the breastfeeding child. On the basis of these considerations, WHO recommends the use of BNT162b2 in lactating women as in other adults. WHO does not recommend discontinuing breastfeeding because of vaccination.”

(If you would like to understand how mRNA Pfizer and Moderna vaccines and the adenovirus vector AstraZeneca/Vaxzevria vaccine work, you might find this article from Healthline helpful.)

Now as I said that document was released on 15th June and one of the larger studies on breastfeeding mothers who’d been vaccinated was released ten days later on 25th June, so perhaps the WHO’s position that “data are not available” may have changed, but that’s the most recent release from them on this topic.

There’s a few research studies now looking at breastfeeding itself when the mother has COVID-19 so let’s start there. I’ll just speak to one of those studies, and you’ll get the idea as to why the World Health Organisation, RANZCOG and the ABA suggests that the benefits of continued feeding if a mother has COVID outweigh the risks, so long as she feels well enough to continue.


A study by Pace and colleagues was published on 9th Feb 2021 titled “Characterization of SARS-CoV-2 RNA, Antibodies, and Neutralizing Capacity in Milk Produced by Women with COVID-19” analysed the breastmilk of 18 women who had mild-to-moderate (that is below hospitalization threshold) level COVID-19. So SARS-CoV-2 is the virus that causes the COVID-19 disease or symptomatic presentation for some people who come into contact with it. In this study 13 of the mums were mixed or combination feeding with breastmilk and either food or formula, and 5 were exclusively providing breastmilk. The authors report that their milk contained specific antibodies to the virus, so SARS-CoV-2-specific IgA and IgG immunoglobulins, but no actual viral particles were present in the breastmilk itself.


They only took 34 samples in this study so it’s pretty small, but interestingly they found that when they tested the milk samples in the lab and looked at the ability of the immune factors in the milk to neutralize the coronavirus in vitro (so in a petri dish), 21 of the 34 samples (so 62%) of the samples they collected could do that where as no pre-pandemic samples they were analysing could do that, so the milk has those adaptive features in it as a result of maternal COVID-19 infection. So it was a really specific response that the mothers’ bodies and milk were developing to exposure to the virus and this was being passed on to their babies. We don’t know how effective that is in helping a real baby’s immune response rather than in a petri dish, or how long these immune factors remain in the breastmilk yet, I couldn’t find that in the data at this point.


They also looked at the health of the babies during the time of the study. 15 of the 18 babies had no symptoms of illness, and 3 had mild symptoms. Only 2 babies in the study actually returned COVID tests that were positive, but only six of them actually got tests at all, I would’ve been really interested to see all the babies got tested but that’s not what happened.

It’s worth noting that the children who were symptomatic with COVID-19 also had other people in their household test positive so may have been exposed to higher viral loading than the asymptomatic ones, but it doesn’t give us a clear breakdown. We also don’t know if that would be different according to which strain of coronavirus we were dealing with. So again this is a really small study, but the babies in this group didn't seem to be too ill when exposed to their mothers having COVID and continuing to breastfeed which is great, and the milk had specific immune factors present without the viral fragments themselves. That conclusion, where the milk had immune factors but not viral fragments, was replicated in other studies as well.

Alright, so if we understand that’s how it works after infection the actual virus, we can start to think about if that same response is replicated after vaccination.

Studies looking at breastfeeding and vaccination have now been done by researchers based in countries including Singapore, Israel and North America. The Pfizer and Moderna mRNA vaccines are the ones generally preferred by health care providers for pregnant and breastfeeding women, and they’re the ones these studies are reporting on.

Obviously in Australia right now we have this issue where breastfeeding women and people who make milk for their babies are specified on the Pfizer eligibility criteria and some people are having difficulty getting hold of Pfizer. Some people are getting the AstraZeneca or Vaxzevria but I don’t have data to tell you about that drug type, so yep, reiterating that this information I’m sharing is about research related to the Pfizer and Moderna vaccine. I should note that the Moderna one is about to be available in Australia pretty soon too if you haven’t heard of that one, it operates in a way that is similar to the Pfizer mRNA vaccine.

So the next article we’ll look at is also from Feb this year, 2021, from Baird and colleagues in Portland, Oregon and they published a paper called “SARS-CoV-2 antibodies detected in human breast milk postvaccination”. So they tracked six lactating women from pre-vaccination through to 14 days after the second dose of the vaccine, so looking at six women who each gave 12 samples each of breastmilk overall across that time period. They too reported significantly elevated levels of the SARS-CoV-2 specific IgG and IgA antibodies in the breastmilk from the sample they took at day 7 after the first dose.

This has been replicated in various other studies, including a really little one by Kelly and colleagues released in March 2021, where they followed 5 women (including one who identified as immunocompromised) and collected specimens of their breastmilk for up to around 80 days from the first dose and the graphs follow a similar trend line for all participants where the SARS-CoV-2 Anti-Spike Protein IgG stabilises from day 30 onwards and stayed the same until they stopped recording at day 80, whereas the IgA level in the breastmilk peaks around day 30 over after the first dose and started to gradually decline which from what I read is sort of what they expected with a maturing immune response. We won’t know how long the immune factor sticks around in the milk until longer term studies are done, but that could be useful info for you if your family is at risk of exposure or perhaps your child is immune-compromised.

So we know vaccination is working in terms of generating an immune response in the mothers and lactating people who get the vaccine, and we know that this is translating to immune factors in the breastmilk as well, so the next thing to ask is – what do we know about vaccine safety for our babies?

There is an article in the journal “Breastfeeding Medicine” from 25th June 2021 by McLaurin-Jiang, Garner, Krutsch and Hale, and that reports on a survey that was voluntarily completed by 4455 breastfeeding mothers who were feeding infants under 2 years of age, and asked them about their own postvaccination symptoms and how their kids were. Most of these mothers were in the US and 83.1% were white women, although there were people in the study group from different races and ethnic groups around the world from Russia to Qatar to Slovakia, Japan, the Phillipines so quite a broad range of places. Maternal side effects were more likely with Moderna than Pfizer, generally temporary things like pain at the injection site, headaches, muscle pain and chils or fevers. 23% of the group who had Moderna reported that their ability to work as reduced, and around 12% said it impacted their household and childcare duties for temporarily, so they felt a bit crap after their vaccine and then it went away. Rates were lower for Pfizer groups but again this was short-lived, and generally more pronounced after the second dose than the first.

90.1% of the 4455 women said milk production didn’t change in the days post vaccination, 3.9% reported an increase in milk productions and 6.0% reported a decrease, unfortunately we don’t know how long they perceived that effect to go for. The authors discuss in the paper why decreased milk production may have occurred for some participants, and you can get the complete text of that article free, so you can explore that one yourself if you like.

The authors note that “Generally, routine vaccination is not contraindicated (so not NOT recommended)  during lactation with the notable exceptions of yellow fever and smallpox vaccines, which are both –live-attenuated vaccines. In concordance, we found that a higher intensity of breastmilk feeding was not associated with more symptoms in the breastfed child. This supports the theoretical knowledge that mRNA-based vaccines would not be transmitted to the child through maternal milk and thus should not cause direct symptoms in the child.”.

So basically, if there was a problem with the drug somehow being bad for baby, we’d expect to see worse symptoms the more milk the infant had, and that didn’t happen.

So did mum getting vaccinated effect the babies?

Now we have to remember this is short-term data, but vaccine side effects if there are any generally come on pretty fast, like within days or even minutes in the case of allergic reactions. So 7.1% of mothers in this study reported some kind of side effect in their children when the mum had her vaccination. Now this sounds bad, but the things they were reporting were like 3.8% of mothers who had the Moderna vaccine said their baby was sleeping more than usual, 3.9% of those who had Moderna said their baby was fussing more than usual, less than 1% of babies whose mums had either vaccine got a fever. And we know that kids are kids and out of 4455 under two year olds, some of this is going to happen anyway in the days post-vaccination. Unfortunately the rates of those things weren’t provided in this data set to compare to, but we do know that nothing major happened to any of the children whose mothers answered the questionnaire.

All in all only 0.2% of mothers who received the vaccination felt strongly that if they had their time again they wouldn’t get it, whereas 89.4% strongly agreed that they would definitely make the same decision again, and the rest fell in to the “agree, neither agree or disagree, or disagree” categories.

Obviously people are concerned about what the vaccine might mean for their babies long term and the short answer is that we don’t have data for that yet. Given how the Pfizer vaccine works and how unstable it is in response to temperatures higher than minus 60 degrees Celsius, I would be surprised if somehow any non-mRNA constituent of the vaccine would somehow elude our body’s defences and scavenger systems to somehow make it into breastmilk, and in any quantity that would survive the baby’s defences in the gastric tract and do harm, but we don’t have long-term data to prove or disprove that.

We would potentially have longer-term data than we currently do if more women and lactating people were involved in early phases of research (which they routinely are not). 2 British doctors, Helen Hare and Kate Womersley, wrote a piece in the BMJ earlier this year after UK regulators had a really conservative approach to vaccination in breastfeeding, compared to the US, Canadian and EU recommendations. In those places people providing milk for their babies were encouraged to weigh up the risks of possible infection to the risks of the vaccination itself and allowed them to get vaccinated if they wanted to, but in the UK breastfeeding people were just straight up excluded in the vaccine rollout even if they were healthcare workers at risk of being frequently exposed to the virus. So they lobbied and got the decision changed so breastfeeding and pregnant individuals could get the vaccine, but they still weren’t overly supported to either, and this quote is from the article they wrote in response:

“This data gap (ie the gap where women and non-cisgender-men, especially pregnant and lactating women and people are not included in early research) is not an anomaly. It is the result of a system of researching and licensing drugs that routinely discriminates against women, excludes them from the evidence base, and denies them the right to make informed choices about their own health. We implore researchers, industry leaders, and the Medicines and Healthcare Products Regulatory Agency (that’s the drug regulator in the UK) to remember that pregnant and breastfeeding women are essential patient populations, not merely women who can wait.”

There are also concerns amongst the parents I’ve been speaking with regarding the safety of getting the AstraZeneca/Vaxzevria vaccine when most people who are breastfeeding are under 50 years of age and up until now the perceived risk of coming into contact with the SARS-CoV-2 virus has been low for many people. I’ll note that the AstraZeneca vaccine uses a more traditional mechanism than the mRNA vaccine we’ve been talking about, and other vaccines of this nature are deemed safe for lactating people and is also highly unlikely to get into breastmilk, but we are awaiting data.

In terms of maternal safety with Vaxzevria/Astrazeneca, according to the Therapeutic Goods Association weekly Covid-19 vaccine weekly safety report released on 26th August 2021, so far in Australia there have been 116 cases including 6 fatal cases of blood clots and low blood platelets (that’s the rare disorder TTS) from 8.8 million doses of that particular type of vaccine and these seem to be more common in women in younger age groups.

This needs to be weighed up against the likelihood of serious disease and hospitalisation with delta as the predominant strain in Australia. A study by Twohig and colleagues released in The Lancet on 27th August 2021, so last week, looked at the rates of hospitalisation when people had lab-confirmed delta strain COVID-19 compared to the alpha strain which was previously the most common one in England. So the study followed 43 338 COVID-19 positive patients, about half had symptoms and half didn’t, between March 29 and May 23 this year. 8682 of those positive people had delta, and 34 656 had alpha.

So what did they find? They found median age of recording positive tests were 31 years for the alpha strain and 29 years for the delta strain. The likelihood of patients needing to be admitted to hospital or attend emergency care within 2 weeks of returning a positive result was 5.7% of patients who had delta compared with 4.2% of patients who had alpha strain.

Those numbers include vaccinated and unvaccinated people lumped together but it just reflects how delta is a more dangerous as well as a more infectious strain. If you are interested, amongst delta group (the people identified as testing positive for delta strain of coronavirus) 74.5% of people they tracked were unvaccinated, 6.4% had received their first dose under 3 weeks ago, 17.8% had received their first dose over 3 weeks ago, and 1.3% were two weeks or more post-their second dose, and it doesn’t break it down into which vaccines they had. The authors note the numbers of vaccinated patients were too small to really establish how protective or otherwise being fully vaccinated was at this stage, but their recruitment numbers here indicate that potentially more unvaccinated people were acquiring the condition in the first place than vaccinated ones.

So as the government’s, at least the NSW government’s, change to “living with COVID” messaging rather than “eradicating COVID” aims, we need to consider what our chances of a breastfeeding-disruptive event like serious illness or hospitalisation might be when we make our safety decisions too. As I said before this video is not to be the sole basis for your decision making, please speak with your health care or medical team and make the choice that is best for you in your personal circumstances.


I hope this blog has given you some information to consider and was useful to you. The references to all the articles are linked in the blog text above and you are welcome to go and read these and many other sources for yourself. Thanks for reading, remember to follow along to get the next updates and share with anyone who you feel may be interested in this information.


This is an updated version of the original transcript published on this website. Information from the paper by Twohig and colleagues has been corrected to reflect ages 31 and 29 as the median age of a positive test result for Alpha and Delta strains of SARS-CoV-2 respectively, rather than median age at hospitalisation as originally stated.


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