This question came up during a course I was teaching recently, and it’s one I tend to hear more on phlebotomy courses than immunisation ones, however it’s worth addressing in the context of medicines too. The situation raised on the course was a client who had turned up at the clinic covered in self-applied EMLA. This left the nurse a bit unsure what to do next:

So:

“If someone uses EMLA before a vaccine, does it stop the vaccine working properly?”

It’s a sensible concern. We are taught to be cautious about anything that might alter the local immune response, and topical anaesthetic creams sit right on the skin where we inject. This study on tattoo ink appeared in November 2025 indicating tattoo pigment may alter immune response and it’s been on my mind. But when you look at the evidence rather than the anxiety, the EMLA picture is actually very reassuring.

What is EMLA doing?

EMLA is a mixture of lidocaine and prilocaine. It works by blocking nerve conduction in the superficial layers of the skin, which reduces pain from needles and other minor procedures. It does not suppress immune cells, and it does not alter the vaccine once it is injected into muscle or subcutaneous tissue. Its action is local and temporary. That distinction matters, because vaccines work by being taken up by immune cells and presented to the immune system — not by whether the skin hurts when the needle goes in.

What have studies actually looked at?

This isn’t just theoretical. Several randomised controlled trials have specifically looked at whether EMLA changes antibody responses to vaccines. These studies were mostly done in paediatric vaccination clinics (because that’s where pain-reduction research has traditionally been focused), but they included both inactivated and live vaccines, including MMR.

The key finding across these trials is consistent: Children who had vaccines with EMLA mounted the same immune responses as those who did not. In other words, numbing the skin did not blunt the body’s ability to recognise the vaccine and produce protective antibodies. This is important, because MMR is a live attenuated vaccine — exactly the type of product people worry about when they think about “local immune effects”. If EMLA doesn’t interfere with immune responses to MMR, there is no plausible reason it would interfere with adult vaccines such as influenza, COVID-19, hepatitis B, rabies, MenACWY or Td/IPV.

But those studies were in children — can we apply them to adults?

Yes, I think so. in this case we reasonably can.

The mechanism of action of EMLA does not change with age. It blocks nerve endings in the skin; it does not block macrophages, dendritic cells or lymphocytes. There is no evidence that adults absorb more of the drug systemically when it is used correctly, and it is not an immunomodulator. In occupational health and travel clinics, we already extrapolate paediatric immunology evidence into adult practice all the time — because immune activation by vaccines is fundamentally the same biological process. If EMLA does not reduce antibody responses in infants receiving MMR and combination vaccines, there is no scientific basis to suggest it would suddenly do so in a 30-year-old having a hepatitis B booster.

What about its use in adult vaccination settings?

In adult clinics, the benefit side of the equation is often more obvious.

We vaccinate:

• needle-phobic staff in occupational health

• people having multiple travel vaccines in one visit

• those undergoing long courses such as hepatitis B or rabies

• staff returning repeatedly for boosters and serology checks

For these groups, pain and anxiety are not trivial. There is good evidence that topical anaesthetics reduce injection pain and improve acceptability of procedures, including in adults. For some people, being able to use EMLA is the difference between completing a vaccine course and avoiding it.

The real-world limitations

The biggest barrier to EMLA in practice is not safety or efficacy — it’s logistics. EMLA needs time to work, usually around 60 minutes for full dermal anaesthesia. That can be awkward in walk-in flu clinics or tightly scheduled OH sessions. It also needs to be removed before skin cleansing and injection, and it should not be applied to broken or irritated skin. Those are workflow issues, not immunology problems.

So what should we be telling patients and staff?

Based on the evidence, the message is simple:

• EMLA does not reduce vaccine effectiveness

• It can be used to improve comfort and reduce distress

• It is particularly helpful for needle-phobic adults and long vaccine courses

• It just needs to be used correctly and planned into clinic flow

For nurses working in GP, travel health and occupational health, this is a useful tool to have — not something to be afraid of.

The next time a patient or colleague asks, “Will this stop the vaccine working?”, the evidence-based answer is: no — it just makes the needle hurt less.

Further reading and evidence:

1) EMLA reduces pain with vaccination

• Cassidy et al. 2001 — Randomised controlled trial: EMLA patch reduced pain during routine immunization in 4–6-year-olds.

• Olsson et al. 2021 — RCT, pneumococcal vaccine pain: Topical lidocaine–prilocaine cream significantly reduced pain expression in infants receiving pneumococcal vaccine.

• Himelstein et al. 1996 — Pain reduction with EMLA: Demonstrates EMLA’s effectiveness in reducing intramuscular injection pain in children (saline surrogate).

• Taddio et al. 1994 — DPT vaccine pain study: Use of lidocaine–prilocaine 5% cream reduces pain associated with diphtheria-pertussis-tetanus immunization.

• Hogan et al. 2010 — Systematic review of pain reduction: Found limited but supportive evidence that lidocaine–prilocaine reduces immunization pain in adults.

2) EMLA does not adversely affect immune response

• Halperin et al. 2000 — MMR immunisation immunogenicity: EMLA patch significantly reduced injection pain with no adverse effect on antibody response to MMR. (Pain + antibody outcome)

• Halperin et al. 2002 — DTaP-IPV-Hib/HepB: EMLA patch reduced pain without affecting antibody response to combination vaccines including hepatitis B.

• Shah et al. 2015 — Review on topical anaesthetics & vaccines: Systematic review summarising multiple trials in children finding no difference in immune response between topical anaesthetic and control groups (Measles-Mumps-Rubella, DTaP-IPV-Hib, Hepatitis B).

3) Practical notes on EMLA pharmacokinetics (safety)

• EMLA SmPC — Systemic absorption and safety profile: Details how lidocaine–prilocaine absorption in adults is low and below toxicity thresholds when used correctly.