Pertussis

Pertussis (whooping cough) is a respiratory infection caused by the bacterium Bordetella pertussis. It has cyclical peaks every 3–5 years. Peaks were seen in 2012 and 2016, but COVID reduced pertussis infections to very low levels. The most recent peak commenced in late 2023. Pertussis is important because it remains a preventable cause of infant hospitalisation and death. Vaccination during pregnancy can provide passive immunity to infants before they complete routine immunisations. With each peak, there are a number of infant deaths, mostly in children born to unvaccinated mothers.

Unfortunately, neither infection nor immunisation provide lifelong immunity, and therefore cycles of pertussis infection continue.

This article was reviewed in September 2024.

This is a summary of the latest on pertussis from the BMJ (BMJ 2019;354:l401) and the UKHSA Guidance on the management of cases of pertussis in England during the re-emergence of pertussis in 2024.

Pertussis summary

Incubation period	4–21d.
Transmission	Airborne droplets.
Prevalence	Peak incidence in childhood is around 6m of age, but remember that 3% of adults presenting to primary care with an acute cough have pertussis.
Presentation	URTI, low-grade fever and cough, followed by classic signs of pertussis: paroxysms of coughing followed by an inspiratory whoop and vomiting. Remember: vaccinated individuals may not whoop but may present with ‘cough, cough, cough, cough, vomit’. You can listen to examples of typical coughs – see link in Useful resources box. May occasionally present with breathlessness, wheeze, fever, flushing and stridor. In infants, may present with difficulty feeding, apnoeic episodes and diarrhoea.
Significance	Causes infant hospitalisation and death. In England, there were 8 reported infant deaths between January and April 2024. The most vulnerable are: Preterm infants aged <2m, regardless of maternal vaccination status. Term infants aged <2m with unvaccinated mother. Infants aged 2 to <5m, regardless of maternal vaccination status. Infants aged 5m to <1y who have not completed primary vaccinations. Vaccination during pregnancy and completing infant immunisations on time (8, 12 and 16 weeks) provides the best protection to infants.
Duration	Colloquially known as ‘the 100-day cough’. Can last 3 months or more.

When to suspect pertussis

The UKHSA guidance states that a suspected pertussis case is when a clinician suspects pertussis! Thankfully, it goes on to give us a bit more detail.

Suspected pertussis may include those presenting with a new cough with no clear alternative cause plus any one or more of:

Paroxysms of coughing.
Post-tussive vomiting.
Inspiratory whoop.
Cough >14d.

OR an epidemiologically-linked case:

Any signs and symptoms of pertussis, and in close contact with a laboratory-confirmed case of pertussis in the past 21d.

Remember that prior vaccination doesn’t preclude infection. A US cohort study suggests that if you assume 95% immunity after 5 doses, the protection offered 5y following the last dose is around 70% (NEJM 2012;387:1012).

Pertussis is a notifiable disease in the UK. Report all suspected cases to your local health protection team. Do not await laboratory confirmation before reporting. Your health protection team will advise on testing.

In the first 21 days, confirmation is with pertussis PCR (throat, pernasal or nasopharyngeal swab or nasopharyngeal aspirate) and culture (nasopharyngeal or pernasal swab). From 2 weeks, testing is via an oral fluid sample (your local health protection team will post an oral fluid kit directly to the suspected case) or serology (blood test). Testing guidelines from the UKHSA can be found here.
Between 2 and 3 weeks, both are offered (PCR and culture, plus either an oral fluid sample or serology).

Treatment

The clinical benefit of antibiotics in pertussis is limited. Benefits are greatest in the early ‘catarrhal phase’ of the illness, but this window of opportunity may be missed because it may not be suspected until later.

Treatment of cases

Group	Time since onset of cough	Action
Pregnant. Where the CASE has close contact with pregnant women or vulnerable infants (including nursery or healthcare workers involved with children aged <3m).	<21 days.	Give antibiotics (beyond 14d, the main benefit of antibiotics is to reduce transmission).
Everyone else.	<14 days.	Consider antibiotics (limited clinical benefit).
Everyone else.	≥14 days.	Do not offer antibiotic.

Treatment of CONTACTS

Antibiotic prophylaxis is offered to close contacts if:

Onset of cough in index case was <14 days ago AND
The close contact is in a ‘high priority group’, defined as ANY one of:
- Unimmunised premature infants born <32w, aged <2m, regardless of maternal vaccination status.
- Unimmunised infants born ≥32w, aged <2m, if mother did not receive vaccination between 16w gestation and 2w prior to delivery.
- Infants aged 2m to <5m, regardless of maternal vaccination or gestational age at delivery.
- Infants aged 5m to <1y who have received fewer than 3 doses of a pertussis-containing vaccine, regardless of maternal vaccination status or gestational age at delivery.
- A pregnant woman 32w gestation or beyond.
- Healthcare workers who care for any of the infant groups mentioned above or pregnant women.
- People who work (regular, prolonged contact) with infants defined above.
- People who share a household with an infant listed in the definitions above.

Additionally, if the CASE is a healthcare worker, further rules apply to cover potential contacts who were patients. We suggest speaking to the UKHSA or occupational health for advice. Prophylaxis beyond close, prolonged household contact has limited evidence of benefit.

Antibiotic doses are the same for prophylaxis as for treatment.

UKHSA-recommended antibiotic regimens

(Guidance on the management of cases of pertussis in England during the re-emergence of pertussis in 2024)

Age group	Clarithromycin	Azithromycin	Erythromycin	Co-trimoxazole (if macrolides contraindicated or not tolerated)
Neonates <1m	Best option 7.5mg/kg bd for 7d	10mg/kg once daily for 3d	10–15mg/kg every 6h for 7d	Not licensed below 6w
Infants (1–12m) and children	Under 8kg: 7.5mg/kg bd 7d 8–11kg: 62.5mg bd 7d 12–19kg: 125mg bd 7d 20–29kg: 187.5mg bd 7d 30–40kg: 250mg bd 7d 12–17y: 500mg bd 7d	1–6m: 10mg/kg od 3d >6m: 10mg/kg od 3d (max 500mg)	1–23m: 125mg qds 7d 2–7y: 250mg qds 7d 8–17y: 250–500mg qds 7d	6w–5m: 120mg bd 7d 6m–5y: 240mg bd 7d 6–11y: 480mg bd 7d 12–17y: 960mg bd 7d
Adults	500mg bd 7d	500mg od 3d	500mg qds 7d	960mg bd 7d
Pregnant women	Third line, dosing as for adults	Second line, dosing as for adults	Preferred – not known to be harmful, dosing as for adults	Should not be used, especially in first trimester, unless no other antibiotic option available

Exclusion

Exclusion aims to limit onward transmission of pertussis.
Note that antibiotics reduce the exclusion period significantly.
Exclusion for contacts is not required.

Population	Exclusion period (whether suspected or confirmed infection)
Children	Can return to school/nursery 48h after starting antibiotics. If NOT treated with antibiotics: can return to school/nursery 14d after onset of cough.
Staff in nurseries/childcare settings/schools	Can return to work 48h after starting antibiotics. If NOT treated with antibiotics: can return to work 14d after onset of cough.
Staff working in nurseries/childcare settings providing close personal care to vulnerable infants	Can return to work 48h after starting antibiotics. If NOT treated with antibiotics: can return to work 21d after onset of cough.
Healthcare workers providing close personal care to vulnerable infants or pregnant women	Can return to work 48h after starting antibiotics. If not treated with antibiotics: can return to work 21d after onset of cough. Inform occupational health and infection control team as soon as possible, even if >21d since onset of cough.

Vaccination in pregnancy

Pregnant women are offered pertussis vaccination between 16 and 32w. This is designed to boost levels of circulating immunity, which can be passed across the placenta and offer passive immunity until primary immunisation of the infant commences at 8w.

Maternal vaccination is more than 90% effective in preventing hospitalisation and death in infants.
Maternal vaccination rates across England in 2024 are <60%.
There is less benefit if vaccination occurs after 32w, but it should still be offered if it has not been done before.
Women should be offered vaccination in EVERY pregnancy.

From July 2024, the preferred vaccine is ADACEL (Tdap) rather than Boostrix IPV (The Green Book). A review of evidence by the JVCI found that infants born to mothers given Boostrix IPV had lowered antibody levels to polio after primary vaccination (although still above the protective threshold). The reduced antibody response to polio has not been seen in the non-IPV-containing ADACEL (Tdap) vaccine. If ADACEL (Tdap) is not available, Boostrix IPV should still be given because the risk of pertussis infection in infants outweighs the potential risk of reduced antibody levels to polio.

Tdap vaccine has been used in maternal vaccination programmes in Europe, the USA and Australia, with good safety and efficacy. Millions of doses have been administered worldwide (UKHSA 2024).

Two large observational studies provide reassuring evidence for the safety of the vaccine in pregnancy.

A large observational study in the UK showed no increased risk of stillbirth, maternal or neonatal death, pre-eclampsia or eclampsia, haemorrhage, foetal distress, uterine rupture, placenta or vasa praevia, caesarean delivery, low birth weight or neonatal renal failure (BMJ 2014;349:g4219).

A large US retrospective cohort study looked at the safety of pertussis vaccination (the US Tdap immunisation). It identified a very small increased risk of chorioamnionitis, and an apparent lower risk of preterm delivery (JAMA 2014;312:1897).
- The authors recommend caution in interpreting the apparent slight increased risk in chorioamnionitis following vaccination, and suggest this could be due to residual confounding and accuracy of the diagnosis. They were also unable to fully correct for bias when assessing the risk of preterm delivery.

Vaccination of healthcare workers and children

Vaccination is also offered to (The Green Book):

Unvaccinated or partially vaccinated children up to 10y.
Some healthcare workers who have not received a pertussis vaccine in the previous 5 years:
- Priority group 1: healthcare workers in close and regular clinical contact with severely unwell infants aged <3m and women in the last month of pregnancy.
- Priority group 2: healthcare workers in regular clinical contact with unimmunised infants in hospital or community settings.
- Eligibility for occupational vaccination is dependent on circulating levels of pertussis. Check UKHSA guidance for full details.

	Pertussis Vaccinated individuals can get whooping cough – they just don’t whoop. Suspect pertussis where there is a history of cough…cough…cough…vomit. Diagnosis can be confirmed by PCR and culture before 3w, or serology or oral fluid sample after 2w. Offer antibiotics to pregnant women and those in contact with vulnerable infants if symptom onset is within 21d, to reduce transmission. The benefit of antibiotics on the clinical course of the disease is limited. Cases should be excluded from work for 48h after commencing antibiotics or 14–21d if untreated. Pregnant women should be offered the vaccine (ADACEL (Tdap)) between 16 and 32w to reduce the risk of transmission to their infant and provide passive immunity. Vaccination should be offered in EVERY pregnancy.
	Are you diagnosing pertussis? Do you have a systematic way of ensuring pregnant women are being offered booster vaccination?
	Useful resources: Websites (all resources are hyperlinked for ease of use in Red Whale Knowledge) Whooping Cough Net - symptoms (examples of full-blown whooping cough and attenuated forms in immunised individuals are available here. There is also plenty of information for patients on this site about why treatment is ineffective, etc. This site is by Doug Jenkinson, a GP in Keyworth, Nottinghamshire)