Printed on: September 26th, 2025

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Chickenpox (including post-exposure prophylaxis in high-risk groups)

Chickenpox (including post-exposure prophylaxis in high-risk groups)

On your triage list: Rabia Khan, 62y, “Babysitting for grandson yesterday and his mum has just called to say he has chickenpox. Mrs Khan doesn’t think she had it as a child. She is on steroids for giant cell arteritis. What should she do?”

This article was updated in July 2025.

Chickenpox became a notifiable disease in the UK in April 2025 (gov.uk - notifiable diseases and how to report them).

There is a chickenpox vaccine licensed for use in the UK. The vaccine is not included in the July 2025 iteration of the routine childhood vaccination programme, although the JCVI supported its inclusion in 2023 (JCVI statement, November 2023). At present, the chickenpox vaccine is only available on the NHS for those in close contact with someone who is at a high risk of serious illness should they contract chickenpox (NHS.uk, accessed July 2025).

The GP contract 2025/26 proposed the introduction of a childhood varicella immunisation programme (and catch-up programme). The go-ahead to introduce a combined measles, mumps, rubella and varicella (MMRV) vaccine from January 2026 was announced by NHS England in August 2025 (GP contract 2025/26, accessed July 2025).

People in these high-risk groups (neonates and infants, pregnant women and immunosuppressed individuals) can experience significant, severe and even life-threatening symptoms if they contract the varicella zoster virus through exposure to a person infected with either chickenpox or shingles.

Post-exposure prophylaxis (PEP) reduces this risk substantially.

Historically, PEP was administered as varicella zoster immunoglobulin (VZIG). As of September 2024, intramuscular VZIG is no longer available in the UK.

This article is based on UKHSA 2023 (updated 2024, 2025) guidance on post-exposure prophylaxis for chickenpox and shingles. While UKHSA guidance applies only to England, this specific guideline is being signposted by public health bodies in Wales and Scotland.

The updates include big changes:

• Oral antivirals (aciclovir or valaciclovir) are now recommended as first-choice PEP for almost everyone who meets the 3 key criteria: high risk + significant exposure + susceptible.
• Oral antivirals should start from day 7 after exposure to day 14 (see below for why!).
• There are two (rare) scenarios in which intravenous immunoglobulin (IVIG) may be given, and we should refer these patients to secondary care:
  • People in whom oral antivirals are contraindicated (see later in article).
  • Neonates who have been exposed to chickenpox from their mother within one week of delivery (either in-utero or post-delivery). This should start as soon as possible after exposure.

This is complicated. If in doubt, we can seek advice from the local health protection team and the duty virologist in secondary care.

This section is adapted from the Varicella chapter of the Green Book, accessed June 2025.

• Chickenpox is an acute, highly infectious illness caused by the varicella zoster virus.
• Typically, it presents with a vesicular rash, preceded by 1–2 days of fever and malaise; however, this prodrome may be absent, particularly in young children.
• Vesicles often first appear on the face and scalp, then spread to the trunk and abdomen; they are more sparse on the limbs. After 3 or 4 days, the vesicles dry with a granular scab, and are usually followed by further crops.
• Vesicles may be so few as to be missed, so numerous that they cover most of the body, or anything in between!
• The infectious period is from 1 to 2 days before the rash appears until the vesicles are dry, but this may be prolonged in immunosuppressed patients.
• The incubation period is 7–21d.
• The secondary infection rate from household contacts may be as high as 90%.
• The incidence of varicella is seasonal, and classically reaches a peak from March to May, although seasonality appears to be becoming less marked.
• Because chickenpox is such a common childhood infection, 90% of adults raised in the UK are immune.
• Chickenpox is currently most common in children <10y, in whom it usually causes mild disease.
• Chickenpox can be more serious in adults, particularly pregnant women, the immunocompromised and those who smoke. There’s also a risk of congenital varicella syndrome in maternal varicella infection, as well as a risk of severe or even fatal disease in neonates exposed to the virus within a week of delivery.

The rest of this article looks at protecting some of these groups via post-exposure prophylaxis.  

The UKHSA guidance outlines which groups should be considered high risk (UKHSA Guidance 2025):

• All are at risk of severe chickenpox and should be risk assessed for PEP if exposed.

• Infection in the first 20 weeks increases the risk of foetal varicella syndrome.
• In the second and third trimester, it can cause severe maternal disease.
• PEP in this group both protects the pregnant woman and may reduce the risk of neonatal infection.

• Infants under 1y may be at increased risk of severe chickenpox. There are three groups at significant risk who are detailed later in this article.
• Neonates in the first 7 days of life are at particular risk of life-threatening complications.

• Oral antivirals may be considered for other groups which may have increased risk for severe disease (such as individuals with neurodisabilities).

Post-exposure prophylaxis is recommended for people who are in a high-risk group AND have had a significant exposure AND are susceptible:

UKHSA guidance states that:

• If the index case with chickenpox is immunocompetent, we can consider them infectious from 24 hours before onset of the rash to 5 days after onset of the rash.
• If the index case with chickenpox is immunosuppressed, we should consider them infectious from 24 hours before onset of the rash until all the lesions have crusted over.

Because in primary care we won’t always know the immune status of the index case, it is reasonable to take the infectious period for ALL infected cases as until the lesions have crusted over. The UKHSA confirmed in direct correspondence that this is a reasonable strategy for primary care.

Neonates, especially in the first week of life, are at higher risk of adverse outcomes (including death) from chickenpox. Infants (under 12m) are also at risk if there is a history of prematurity (UKHSA guidance 2025). We strongly recommend that you seek advice from paediatrics if you have any doubts/concerns.

Key facts:

• If the mother has ever had chickenpox or shingles (even many years ago), or she has a clear history of having received two doses of the varicella vaccine, the infant will have some maternal antibody protection.
  • The exception to this is premature infants, where placental transfer may not have occurred. (Elsewhere in its guidance, the UKHSA identifies prematurity meeting the threshold for treatment as infants born <28w gestation. It isn’t clear in this section of the guidance whether the UKHSA is using the same age cut-off for this advice, but we suspect it is) – see flowchart below for more details.
• The neonates at highest risk are those whose mothers develop chickenpox in the 7d before or 7d after delivery, when the baby will have no maternal or self-generated immunity. The mother developing shingles in this time is NOT a risk – it confirms maternal past infection (and therefore maternal immunity).
• Babies exposed to chickenpox within the first 7 days of life from a source other than the mother are also at risk if there is no or uncertain maternal immunity. Mothers with uncertain immunity are:
  • Those who have never had chickenpox/shingles AND have an absent or uncertain vaccination history.

The UKHSA guidance says:

Post-exposure prophylaxis is NOT usually recommended if:

• Neonates >7d of age are exposed to chickenpox or shingles (from any source) UNLESS at risk for another reason (e.g. history of prematurity, immunosuppressed, severe congenital/underlying condition, in hospital since birth – see the 'Does this person need PEP' image for details).

There are two types of VZV IgG blood tests:

• Qualitative: can come back as positive/negative or equivocal.
• Quantitative: gives an exact measure of VZV IgG levels.

Direct correspondence with the UKHSA says that usually, if requested urgently, VZV IgG blood results should be available within 24–48h of the sample being received in the lab. This means we would normally get results back quickly enough to make a clear decision before starting oral antivirals on day 7 after exposure.

But (you knew it was coming!), currently, some areas only have access to qualitative tests so may then send the sample on to a different lab for quantitative testing. This adds delay.

For this reason, the UKHSA states that if quantitative levels will not be available within 10 days of the initial exposure and the initial qualitative result was negative, we should start oral PEP (or IV therapy in secondary care) based on the qualitative result alone.

Again, if you are unsure, seek specialist advice.

Oral antivirals are first-choice PEP for everyone except neonates and people who have a contraindication, who should be offered IV therapy.

Choose oral aciclovir or valaciclovir. Valaciclovir may be better tolerated due to fewer side-effects and reduced frequency of dosing; it also shows improved bioavailability so may be the preferred choice, depending on your local formulary.

IMPORTANT: these should be given:

• From day 7 to day 14 after exposure:
  • If the person who needs PEP lives with the index case, class the date of exposure as the day the rash started.
  • If the person who needs PEP has had multiple exposures, count from the first exposure.
• If the person presents after day 7 of exposure, a 7-day course can be started up to 14 days after exposure.

Why? The UKHSA guidance states that there is evidence that starting the course 7 days after exposure is more effective at reducing the incidence and severity of varicella infection than starting it immediately. This was a small study but showed that 77% of those given aciclovir immediately developed clinical varicella compared with 21% who started it on day 7 (Arch Dis Childhood 1993;69(6)639).

Remember, neonates exposed to maternal disease within 7 days of birth are the exception here: they need to start treatment as soon as possible.

(Note: for aciclovir, this differs slightly from therapeutic dose and is off label. Neither drug is licensed at all for use in pregnancy, but both uses are advised by the UKHSA (BNF accessed June 2025)).

If the person is exposed again, further courses of antivirals can be prescribed – again, starting 7 days after exposure.

This is only indicated in:

• People in whom oral antivirals are contraindicated, or if a person cannot take/absorb them, e.g. hyperemesis, active inflammatory bowel disease or renal impairment (see BNF for specifics). These people should be given ‘normal’ IV immunoglobulin.
• Neonates who have been exposed to chickenpox from their mother within one week of delivery (either in-utero or post-delivery). In this scenario, varicella-specific IV immunoglobulin is given alongside IV antiviral treatment, and should start as soon as possible after exposure.

When intramuscular VZIG was in use, primary care clinicians were expected to source this from the UKHSA and administer it. Now that it’s been replaced by an intravenous drug, in the rare scenario it’s needed, we’ll need to refer these patients to secondary care. We suggest you speak to your duty virologist or local health protection team to find out how best to arrange this locally. The table below has some basic information about use of IVIG:

This is quite a big change in practice and something we won’t encounter very often. If we are unsure and require advice, direct correspondence with the UKHSA guidance states that we can seek advice from:

• Duty virologist in secondary care.
• Our local health protection team.

The UKHSA guidance states that if, despite appropriate prophylaxis, a high-risk person presents with a chickenpox rash, they should be changed onto a therapeutic dose of oral antivirals, starting from the day of onset of the rash, and that if severe chickenpox develops, they will need admission. The UKHSA doesn’t define ‘severe chickenpox,’ and we’d suggest that you have a very low threshold for discussing any high-risk patient with chickenpox with secondary care.

Neonates presenting with chickenpox will need admission for IV treatment as soon as possible.

Concerns have been expressed for some time about evidence of an association between exposure to NSAIDs during a varicella zoster infection and increased risk of invasive group A streptococcus or other severe skin and soft tissue infections.

Several mechanisms have been postulated and in vitro experiments performed (Curr Opin Infect Dis 2015;28:231):

• The anti-inflammatory action of NSAIDs may mask the symptoms of invasive skin infections in their early stage.
• In vitro, NSAIDs seem to accelerate progression of invasive skin infections, increase bacterial numbers and reduce the effectiveness of antibiotics.
• NSAIDs delay muscle and skin regeneration and repair.

There are no official UK, Welsh or Scottish guidelines on the management of pain in acute varicella infection.

CDC guidance (accessed June 2025):

• Makes clear recommendations that NSAIDs should be avoided for both pain relief and fever management in chickenpox.
• Does not give the same advice in shingles, advising over-the-counter pain relief as an option.

This is an area of imperfect evidence – almost all the studies are case–control methodology, which means they can only demonstrate an association. An excellent summary paper reviewed the current evidence (Arch Dis Child 2017:102(10):988).

Only one study was based in primary care. It was a UK-based GPRD study of more than 240 000 children and adults with either chickenpox or shingles (Br J Clin Pharmacol 2008;65(2):203).

It showed that:

• There is between a 2- and 5-fold increase in the risk of invasive skin conditions with NSAID use.
• The risks were higher in chickenpox (RR 4.9, CI 2.1–11.4) and lower in shingles (RR 1.6, CI 1.1–2.4).
• No increased risk was seen with paracetamol use.
• The absolute risk of severe skin infection is low (about 3/1000 cases in chickenpox and about 6/1000 cases in shingles).

The summary paper concludes that a causal relationship between NSAIDs and infectious complications cannot be excluded, and that we might also consider that children with varicella who require an NSAID (in addition to paracetamol) should be considered as at higher risk of developing infectious complications (Arch Dis Child 2017:102(10):988).

Given that paracetamol is a perfectly valid option for most children with chickenpox, it seems reasonable for us to recommend this – and to be aware that if paracetamol alone (along with other self-care measures) isn’t sufficient to manage pain and distress, the child needs a clinical review because they may be at higher risk of developing infectious complications.

Conversely, in the scenario of a well-sounding child with chickenpox whose parent has given ibuprofen because, perhaps, it’s all they had in the cupboard, and who contacts us concerned because they’ve then read the advice against doing this, we can likely be reassuring given that the absolute risk of severe skin infection is low.

The primary care cohort study outlined above showed that the overall risk of skin infection is lower for shingles than chickenpox (Br J Clin Pharmacol 2008;65(2):203). The relative risk increase is only 1.6, with a confidence interval of 1.1–2.4 on a background risk of 6/1000, so the absolute risk increase is small.

Most of the cases of skin infection identified in the study were in those under the age of 12, and shingles is more commonly a disease of the older adult. For this reason, the authors limited their recommendations to children.

	Chickenpox (including post-exposure prophylaxis in high-risk groups) Chickenpox is now a notifiable disease. When it comes to exposure… If your patient is a neonate who has been exposed via their mother within 7 days of birth (either in-utero or post-delivery), do not pass go! Admit to paediatrics immediately. For everyone else, remember the 3 high-risk groups: immunocompromised, pregnant, those under 1y of age. Assess if all the following 3 criteria are met. If so, offer PEP: Are they in a high-risk group? Have they had a significant exposure during the infectious period? Are they susceptible to infection? Oral aciclovir or valaciclovir are first choice for PEP initiated in primary care, and should start on day 7 after exposure. Do not recommend or prescribe NSAIDs for pain or fever relief in chickenpox.
	Share this learning with your team. Would high-risk people be spotted in the triage list?
	Useful resources: Websites (all resources are hyperlinked for ease of use in Red Whale Knowledge) UKHSA guidance on post exposure prophylaxis for chickenpox and shingles Telephone Rabies and immunoglobulin service, UKHSA telephone: 0330 1281020