Every now and again, two bits of perfectly sensible vaccine guidance collide.

This is one of those situations.

Imagine a pregnant woman attends for travel advice. She is around 20 weeks pregnant, has not yet had her pertussis vaccine in this pregnancy, and her travel risk assessment shows that she also needs a polio-containing vaccine. We know that the routine maternal pertussis vaccine is now ADACEL. We know that ADACEL deliberately does not contain polio. And we know that if a pregnant traveller requires polio protection, Revaxis can be given.

So do we give ADACEL now and Revaxis as a separate vaccination?

Or, if she is due both at the same time, could we use Boostrix-IPV or REPEVAX and cover pertussis and polio with one vaccine?

It is a slightly niche scenario - but exactly the sort of thing that can crop up in a travel consultation and make you stop and think.

I think it is worth understanding why ADACEL became the preferred vaccine in the first place before deciding what makes sense for the individual woman.

Why did we switch to ADACEL?

Until July 2024, the UK maternal pertussis programme routinely used a vaccine that also contained inactivated poliovirus vaccine (IPV). That worked extremely well as a pertussis programme. Maternal vaccination produces antibodies which cross the placenta and protect the newborn during those vulnerable first weeks of life before the infant starts their own vaccination programme.

However, studies looking at infants whose mothers had received an IPV-containing pertussis vaccine during pregnancy found something interesting. When those babies subsequently received their own routine polio-containing vaccines, their antibody responses to poliovirus were somewhat lower than those seen in infants whose mothers had not received IPV during pregnancy. This effect is known as blunting.

The effect was seen against poliovirus types 1, 2 and 3, with type 2 particularly affected. Importantly, this did not mean the babies were left unprotected. Antibody levels remained above the protective threshold, and the clinical significance of the finding remains uncertain. Nevertheless, if millions of pregnant women are being vaccinated through a national programme, and the IPV component is not actually needed by the vast majority of them, there is little advantage in including it. JCVI therefore advised a preference for a pertussis vaccine without IPV, and from July 2024 ADACEL became the vaccine supplied for the maternal programme.

That is the important word here: preferred.

It does not mean that Boostrix-IPV or REPEVAX suddenly became unsafe in pregnancy. They didn't. UKHSA specifically states that both remain suitable, safe and effective for use in the prenatal programme.

So when might we still use Boostrix-IPV or REPEVAX?

There are already circumstances in national guidance where an IPV-containing pertussis vaccine should be used instead of ADACEL. The clearest example is severe latex allergy. The tip cap of the ADACEL pre-filled syringe contains a natural rubber latex derivative. Boostrix-IPV and REPEVAX have synthetic rubber tip caps which do not contain dry natural rubber latex, and UKHSA advises using one of these vaccines instead in a pregnant woman with a known severe latex allergy.

They can also be used if ADACEL is unavailable and obtaining it would cause a delay in maternal pertussis vaccination. The priority is not to miss or delay protection against pertussis simply because the preferred product is unavailable.

But there is another situation that I find particularly interesting: What if she actually needs polio as well?

UKHSA guidance already considers pregnant women who have an incomplete or uncertain tetanus, diphtheria and polio vaccination history. If a woman reaches 16 weeks of pregnancy while completing such a course, UKHSA says her pertussis-containing dose should ideally be a dTaP/IPV vaccine. Why? Because that one vaccine provides the maternal pertussis dose and counts towards her required polio vaccination. In fact, the guidance specifically says that if she is being vaccinated in primary care, dTaP/IPV should be offered for this reason.

That gives us an important clinical principle. When a pregnant woman genuinely needs both pertussis and IPV, it can make sense to use one vaccine containing both rather than automatically splitting the two indications into separate vaccinations.

And that is where travel health becomes interesting.

The pregnant traveller

NaTHNaC quite rightly reminds us that the recommended maternal pertussis vaccine no longer contains polio. Its pregnancy guidance states that where polio protection is required for travel, an additional vaccination with Revaxis will be needed. It also advises that women who need tetanus, diphtheria or polio protection for travel before 16 weeks' gestation should receive Revaxis and then receive their routine maternal pertussis vaccination at the appropriate gestation, with a minimum four-week interval recommended.

That makes complete sense before 16 weeks.

Giving an IPV-containing pertussis vaccine at, for example, 10 weeks would not remove the need for the maternal pertussis dose later in pregnancy. The pertussis dose needs to be appropriately timed to optimise placental antibody transfer.

So:

Before 16 weeks + polio required for travel = Revaxis. She can then receive her routine maternal pertussis vaccination at the appropriate time.

But what if she is already 20 weeks pregnant? Her maternal pertussis vaccination is due now. Her travel-associated IPV is due now.

That feels different. ADACEL + Revaxis, or one dTaP/IPV?

If ADACEL has already been given, I think this is straightforward. There is no obvious reason to give another pertussis-containing vaccine simply because IPV has subsequently become indicated. Give the required polio-containing vaccine - usually Revaxis - according to the appropriate guidance.

But if she has not yet had her maternal pertussis vaccine, and is at an appropriate gestation for it, I think it is reasonable to stop and consider whether an IPV-containing pertussis vaccine might make more clinical sense.

For example:

A woman is 22 weeks pregnant. She has not yet received her pertussis vaccine. Her travel assessment identifies a genuine indication for IPV.

One option is:

• ADACEL + Revaxis: Two injections, both containing tetanus and diphtheria antigens, potentially requiring additional appointment planning.

Another potential option is:

• Boostrix-IPV or REPEVAX. One injection providing the required maternal pertussis vaccination plus IPV.

We already know these vaccines are considered suitable, safe and effective in pregnancy.

We also know UKHSA recommends exactly this type of approach when the woman needs polio vaccination because her routine vaccination history is incomplete. So clinically, the reasoning is not particularly radical.

But does the guidance actually tell us to do this for travel?

This is where I would be careful. I cannot currently find national guidance which explicitly states: “If a pregnant traveller aged 16+ weeks requires IPV, replace ADACEL with Boostrix-IPV or REPEVAX.”

NaTHNaC's wording is more straightforward: the recommended pregnancy vaccine does not contain polio, and if polio protection is required for travel an additional Revaxis vaccination will be needed. At the same time, UKHSA's more detailed maternal programme guidance clearly demonstrates that an IPV-containing pertussis vaccine can be deliberately selected when the woman independently needs IPV.

So I think there is a gap between the very specific travel-health wording and the broader clinical principles in the immunisation guidance.

For me, this is a situation for individual assessment rather than an automatic vaccine swap.

The reason for the IPV matters. The woman's gestation matters. Whether the maternal pertussis vaccine has already been given matters. Her previous tetanus, diphtheria and polio history matters. And the legal mechanism under which the vaccine is being administered matters too.

Don't forget the PGD

This is an important practical point.

The current UKHSA maternal pertussis PGD template permits Tdap or dTaP/IPV where Tdap is clinically unsuitable, and includes ADACEL, Boostrix-IPV and REPEVAX. However, the national document is only a template; organisations must authorise their own PGD before it can be used. I would therefore not simply assume that “she needs polio for travel” automatically fulfils the wording of every locally authorised maternal pertussis PGD.

Check it.

Depending on the service and circumstances, an appropriate PSD or other prescribing mechanism may be required. This is one of those situations where the clinical decision and the legal mechanism need to agree with one another.

What about the blunting?

This is probably the obvious question. If we deliberately moved away from IPV-containing pertussis vaccines because of blunting, why would we voluntarily give one?

Because risk-benefit decisions change when the woman actually needs IPV.

The rationale for ADACEL at population level is very sensible: there is no reason to give millions of women an additional IPV antigen they do not require if removing it may optimise their infant's subsequent antibody response. But that is different from an individual pregnant traveller who has a genuine indication for IPV. The potential blunting effect does not make IPV-containing pertussis vaccines contraindicated in pregnancy. UKHSA continues to describe Boostrix-IPV and REPEVAX as safe and effective alternatives, and the observed infant polio antibody responses remained above the protective threshold.

There is now another reassuring bit of context too.

From January 2026, the routine childhood programme includes an additional hexavalent DTaP/IPV/Hib/HepB dose at 18 months, giving children another opportunity to boost their polio immunity. That doesn't make the rationale for choosing ADACEL disappear - it remains the preferred routine maternal product - but it is useful context when discussing what “blunting” actually means. It is not the same as saying that giving IPV during pregnancy harms the infant or leaves them unprotected.

A practical way to think about it

My approach would be:

Polio needed before 16 weeks: use Revaxis where indicated, then give the routine maternal pertussis vaccine at the appropriate gestation. NaTHNaC recommends a minimum four-week interval.

16+ weeks and ADACEL has already been given: if IPV subsequently becomes indicated, use the appropriate polio-containing vaccine rather than repeating pertussis unnecessarily.

16+ weeks, pertussis has not yet been given, and IPV is also genuinely required: pause and consider whether one dose of Boostrix-IPV or REPEVAX could appropriately fulfil both indications, taking account of current guidance and the legal mechanism being used.

No actual indication for IPV: use ADACEL as recommended by the routine maternal programme.

Severe latex allergy to the ADACEL presentation: use Boostrix-IPV or REPEVAX in accordance with UKHSA guidance.

ADACEL unavailable and obtaining it would delay vaccination: an IPV-containing pertussis vaccine is preferable to delaying or missing maternal pertussis vaccination.

The bigger lesson

This is one of the reasons I love travel health. Sometimes the answer isn't found on one page of one guideline. We might be simultaneously considering the routine immunisation programme, pregnancy guidance, travel-health recommendations, vaccine product choice, timing, previous vaccination history and the legal mechanism for administration. ADACEL is absolutely the preferred vaccine for the routine maternal pertussis programme. But “preferred routinely” and “the only appropriate vaccine in every individual circumstance” are not quite the same thing. When a pregnant woman also has a genuine indication for polio vaccination, it is worth noticing that Boostrix-IPV and REPEVAX still exist in the pregnancy guidance for a reason.

Sometimes the best question isn't simply:

“What vaccine do we normally use?”

It is:

“What does this particular patient actually need today?”