Following a change in official guidance in April, people who are breastfeeding in the UK have now been given the green light to receive a covid-19 vaccination. This is great news. But in the absence of any clinical trials proving that it is safe to have a covid-19 vaccine while breastfeeding, the onus appears to be on new parents like me to decide for themselves whether to go ahead and get jabbed. I took a break from nappy changes and nap schedules to find out what research we have to go on.

When it comes to safety for breastfed babies, “the vast majority of vaccinations are overwhelmingly safe”, says Natalie Shenker at Imperial College London. For example, people who are about to travel can receive vaccines for hepatitis B, among other diseases, while breastfeeding.

Shenker says there have only ever been two case reports of harm to an infant after a breastfeeding parent has been vaccinated, both from the live yellow fever vaccine. This vaccine, and the live smallpox vaccine, aren’t usually offered to those breastfeeding, but previous research shows that all the standard, non-live types of vaccine don’t get into breast milk, and we can probably expect this to be true for the more traditional covid-19 vaccines, such as the Oxford/AstraZeneca and Johnson & Johnson jabs. If no components make it into the milk, there is no way a vaccine could harm a baby.

What about mRNA vaccines, like Pfizer/BioNTech and Moderna, which use new vaccine technology? There are no worrying signs so far. In March, Yarden Golan at the University of California, San Francisco, and colleagues shared their findings that, between 4 to 48 hours after vaccination, no mRNA associated with the vaccine could be detected in the breast milk of five Pfizer/BioNTech recipients and one Moderna recipient. The study is very small, and not yet peer reviewed. Golan says the team is doing a larger study involving 143 pregnant and lactating women.

As for side effects, Shenker told a recent online event hosted by the campaign group Pregnant Then Screwed that the UK’s yellow card system (which enables the public to report adverse events to any drug) hasn’t detected any significant spikes in side effects among those breastfeeding. “There have been a few women reporting that their supply has decreased, that they’ve developed mastitis, or that they’ve developed breast pain, and a few have reported children who’ve had rashes or a low-grade temperature, or even a bit of diarrhoea,” said Shenker. “However, these numbers are tiny, given the number of women being vaccinated, and it’s likely that these events might have happened anyway.”

After giving birth, people are temporarily at higher risk than normal of blood clots, so should they be wary of clotting problems associated with vaccination? Speaking at the same event, Jo Mountfield, vice president of the Royal College of Obstetricians and Gynaecologists (RCOG), said that the clotting issue associated with the Oxford/AstraZeneca vaccine is an immune response unrelated to the increased risk of clotting experienced postnatally.

However, everyone under the age of 40 in the UK should now be able to opt for the Pfizer/BioNTech or Moderna jabs instead of the Oxford/AstraZeneca vaccine, if they prefer.

Read more: Everything you need to know about covid-19 vaccines for children

I feel reassured that my vaccination is unlikely to harm my baby – but could it also protect her? A study published in March, which looked at 31 lactating women who received the Pfizer/BioNTech or Moderna vaccines, detected vaccine-generated antibodies against covid-19 in all breast milk samples. A second study, published in April, analysed milk samples from 84 women who had received two doses of the Pfizer/BioNTech vaccine, 21 days apart. It found high levels of a type of antibody called IgA in the milk, two weeks after the first dose. IgA antibodies are one of our body’s first lines of defence, helping prevent infections from passing through membranes and getting into the body.

Ilan Youngster at the Shamir Medical Centre in Israel, who worked on the second study, says that we already know from other respiratory diseases like influenza and pertussis that IgA antibodies in breast milk can help protect babies from getting infected, and that the team believes covid-19 is unlikely to be different. He adds that there were three covid-19 outbreaks in families in the study in which an older sibling became ill but the breastfed baby didn’t. “This is obviously not empirical proof, but is still a nice anecdote,” he says.

There is some research to support this. In a non-peer reviewed study, Yariv Wine at Tel Aviv University in Israel and colleagues tested the antibodies found in the milk of 10 women who had received both doses of the Pfizer/BioNTech vaccine. They showed that antibodies from all of the women seemed to be capable of neutralising the SARS-CoV-2 coronavirus.

IgA antibodies protect the nose and breathing passages, so Youngster thinks that any antibody protection from breast milk is likely to only work in this area – which is the usual site of covid-19 infection – and that protection would probably only last for as long as an infant is breastfeeding. Once an infant is fully weaned, these antibodies decay.

Read more: Everything you need to know about covid-19 vaccines for children

Any protection to the baby would also only last for as long as these antibodies continue to transfer into milk. Wine says that previous studies of vaccines for other diseases have found that vaccine-specific antibodies can persist in breast milk for at least one year, but that we don’t know yet if this could be the case for covid-19 vaccines.

So far, this kind of research has mostly taken place in Israel and the US, where the Pfizer/BioNTech or Moderna vaccines have been given to those breastfeeding for long enough for such studies to take place. We don’t know yet if other vaccines, such as the Oxford/AstraZeneca jab, also lead to a transfer of antibodies in breast milk, but it hopefully won’t be too long before we find out.

The growing body of research around covid-19 vaccine-induced antibodies in breast milk hasn’t gone unnoticed, and some parents are wondering whether, after getting vaccinated, they should give some breast milk to their older children too. Others who have recently stopped breastfeeding are trying to make themselves lactate again. It is an interesting idea, but there are no studies looking into this as yet. If you have medical concerns you should consult a medical practitioner.

I will have a vaccine as soon as I am offered it – preventing myself from getting ill is the most important thing I can do for my daughter. As for breastfeeding, I am undecided. The circumstantial evidence around the safety of continuing with breastfeeding after vaccination is reassuring. And the hints that my vaccine antibodies could protect my baby even have me wondering whether I should continue breastfeeding for longer than I had originally planned.

If you choose to have the vaccine while breastfeeding, one suggestion from several experts at the online event was to try to schedule your jab at least a week before or after any scheduled immunisations for your baby. This will avoid confusing you and your baby’s immune responses to each vaccine, so that you both get the maximum benefit from each jab.