Pertussis

New Zealand has continued to experience cyclic outbreaks of pertussis, occurring every few years, in recent decades. This is in part due to historically low immunisation rates and because immunity from both natural infection and immunisation wanes over time.

More detailed epidemiological information is available on the Institute of Environmental Science and Research (ESR) surveillance website.

The objectives of surveillance for pertussis are:

• to monitor and analyse the epidemiology of the disease, with emphasis on those at high risk of severe disease or complications, particularly infants
• to monitor the impact of immunisation
• to report on findings to inform effective and efficient prevention strategies.

The priority of the prevention strategies against pertussis is to protect infants by passive immunity transfer from their mothers with booster immunisation during each pregnancy, and timely immunisation of infants.

Usually 7–10 days, ranging from 5–21 days.

Droplets of respiratory, oral or nasal secretions. Indirect spread via contaminated objects occurs rarely.

Highly communicable in the catarrhal stage before the paroxysmal cough stage, and during the first 2 weeks of the paroxysmal stage of the cough. Transmissibility gradually decreases after that.

For control purposes, the communicable stage lasts from the catarrhal stage to 3 weeks after the onset of paroxysmal cough in a case not treated with antimicrobials. When treated with an effective antibiotic (eg, azithromycin), infectivity lasts until 2 days of antibiotics have been taken. This lengthens to 5 days if other antibiotics are used (eg, erythromycin).[3]

Confirmed: a person who has laboratory definitive evidence; OR, a person who has a clinically compatible illness AND who has an epidemiological link to a confirmed case.

Probable: a person who has a clinically compatible illness AND either has:

• a cough lasting 14 days or more OR
• exposure as part of an outbreak (i.e. an institutional outbreak or community-wide outbreak [when there is limited access to testing]).

Under investigation: a person who has been notified, but information is not yet available to classify further.

Not a case: a person who has been investigated and subsequently found not to meet the case definition.

A clinically compatible illness is characterised by a new onset cough without a clear alternative cause and one or more of the following features:

• paroxysms of coughing
• cough ending in vomiting
• inspiratory whoop
• apnoea or cyanosis (in infants aged under 12 months).

An epidemiological link is established when there is contact between two people at a time when one of them is likely to be infectious (from the catarrhal stage, approximately 1 week before, to 3 weeks after onset of cough) AND:

• the other has an illness which starts within 5 to 21 days after this contact,

AND

• at least one case in the chain of epidemiologically linked cases (which may involve many cases) has laboratory definitive evidence of pertussis.

Laboratory definitive evidence

Detection of Bordetella pertussis nucleic acid by polymerase chain reaction (PCR), OR

Isolation of B. pertussis (see Laboratory testing guidelines).

Health practitioners should notify the local medical officer of health on suspicion of Bordetella pertussis during the initial assessment of the person.

If B. pertussis is suspected, include clinical information, symptom onset and vaccination status on the sample request form.

In periods of low pertussis activity, the medical officer of health or other public health service staff may discuss urgent cases with the on-call clinical microbiologist, where there is a high index of suspicion for B. pertussis, so that laboratory staff are aware of the urgency and can prioritise the sample for prompt processing. Testing may not be necessary for cases with an epidemiological link to a confirmed case.

In periods of high pertussis activity, testing may not require discussion with the medical officer of health. Testing should be prioritised towards protecting high priority contacts from infection - especially infants and pregnant people. Testing is not required for cases with an epidemiological link to a confirmed case.

For further guidance on the groups that should continue to be tested in periods of high pertussis activity, please refer to the following: Guidance for prioritisation of testing in periods of high pertussis activity.

Note: There are several laboratory tests available for the diagnosis of B. pertussis and the timing of the test impacts on its sensitivity. A negative test does not necessarily rule out B. pertussis: consider exposure, clinical compatibility, the test used and the timing of the test. For further testing advice please contact the clinical microbiologist. There is no reliable serological test for acute infection or immunity to B. pertussis.

For urgent polymerase chain reaction (PCR) processing the medical officer of health should discuss with the clinical microbiologist. The turnaround time for a prioritised test may still take 24-36 hours after arrival at the laboratory.

1) Bordetella pertussis polymerase chain reaction (PCR) 

Bordetella pertussis PCR is the recommended test for diagnosing the bacteria B. pertussis in people where the symptoms have been present for less than 3 weeks. Positive results are more likely within 10-14 days of symptom onset. After 4 weeks of cough, the amount of bacterial DNA in the nasopharynx rapidly diminishes, increasing the risk of a false-negative result. [1, 2, 3]

PCR testing ensures a fast turnaround time when rapid confirmation of the diagnosis is likely to change management of the case or their contacts. 

2) Serology

Most laboratories in Aotearoa New Zealand do not offer serology testing for B. pertussis.

• Serology (Immunoglobulin G IgG)

Serology is not recommended, except when requested by a medical officer of health after discussion with a clinical microbiologist if the use of a PCR test is not possible. This is because the sensitivity and specificity of serology is low and cannot be used as a confirmatory test of infection or vaccination. The presence of B. pertussis IgG is not a reliable indicator for a person’s immune status and should not be used in this context.

3) Culture

Culture is no longer routinely performed for diagnostic purposes. PCR testing is between two and six times more sensitive than culture and is the preferred diagnostic method.

Attending medical practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification should not await confirmation.

Any person awaiting a pertussis test result should be advised to stay at home and away from work, school, early childhood services, or other institutions while they await their test results.

See Appendix 5: Escalation pathways for more information

The goal of public health action for pertussis is to reduce onward transmission to protect individuals at risk of severe pertussis outcomes, especially infants who have received fewer than 3 doses of a pertussis-containing vaccine. Therefore, the following cases should be prioritised for follow-up:

• Infants aged under 12 months who have received fewer than 3 doses of a pertussis-containing vaccine, especially those aged under 6 months and/or Māori and Pacific infants.
• Pregnant people in their last trimester of pregnancy, especially Māori and Pacific pregnant people.
• People who regularly interact with groups at high risk of severe outcomes from pertussis (e.g. healthcare workers who regularly interact with infants aged under 12 months and/or pregnant people in their third trimester).
• People with health conditions that put them at risk of severe disease (e.g. respiratory and/or immunocompromising conditions).

The investigation and management will usually be carried out by the treating clinician. The following information should be checked and recorded as part of the investigation:

• Pertussis immunisation status (for infants aged under 12 months this information should include antenatal immunisation status and number of doses since birth).
• Ethnicity.
• Pregnancy status.
• Occupation (and whether they routinely interact with any of the groups at high risk of severe outcomes from pertussis identified above, including infants aged under 12 months or pregnant people in their third trimester).
• Any priority close contacts for whom antibiotic prophylaxis would be prescribed, should be considered (especially household contacts who are either infants aged under 12 months or pregnant peoples in their third trimester).

Testing may not be necessary (or appropriate) for cases with an epidemiological link to a confirmed case or in outbreak situations. See the laboratory testing guidelines for further information.

Any person awaiting a pertussis test result should be advised to stay at home and away from work, school, early childhood services, or other institutions, while they await their test results.

Infectious cases should be excluded from work, school, preschool, and child-care, and have restricted attendance at other settings, especially where there are infants or pregnant people in their third trimester, until they are no longer infectious, i.e. until whichever comes first of:

• 21 days after the onset of any cough, or
• 14 days after the onset of paroxysmal cough (if the onset is known), or
• they have completed at least 2 days of a treatment course of azithromycin, or 5 days of a different antibiotic (co-trimoxazole or erythromycin).

In hospital settings, management of infectious cases should also include droplet precaution measures and accommodation in a single room. Some contexts may require restriction of infectious cases in hospital settings for longer than 2 days, even when azithromycin is prescribed. The appropriate timeframe for restriction in these contexts is at the discretion of the Infection Prevention Control (IPC) team and will be determined by an IPC risk assessment.

The benefits of treatment for pertussis are greatest when antibiotics are initiated as soon as possible after symptom onset. The recommended antibiotics for treatment of pertussis are azithromycin or cotrimoxazole (see Table 2).

Antibiotic therapy administered within the first 1-2 weeks of symptoms (in the catarrhal stage) may modify the clinical course of the illness (based on suboptimal evidence). Antibiotic therapy administered after the onset of the paroxysmal cough does not reduce duration of illness.

Treatment for pertussis reduces the time a case is infectious. For the purpose of reducing transmission, antibiotic therapy is recommended for cases up to 3 weeks after the onset of cough.

There is no evidence that initiating treatment after 21 days following the onset of cough will modify the clinical course of the illness or reduce infectivity.

Antibiotics may be indicated before test results are received (or in situations where testing is not being done) if the clinical history is strongly suggestive of pertussis or the person is at high risk of severe or complicated disease (e.g. an infant). [4,5,6,7]

Table 2: Recommended dosage of antibiotic therapy for cases

Infants must be closely observed while on any of these antibiotic treatments. Azithromycin is associated with hypertrophic pyloric stenosis in infants aged under 6 weeks. Therefore, monitoring all cases for complications is recommended for 4 weeks after completing treatment.

See the New Zealand Formulary, New Zealand Formulary for Children and medicine data sheets for more details, including the use of antibiotics during pregnancy, or consult an infectious diseases physician or obstetrician.

Provide the case or relevant caregiver with the case information letter and pertussis information sheet which provides guidance on pertussis, isolation requirements and precautions that can prevent transmission to others. The case or relevant caregiver should be advised about the nature of the infection and the mode of transmission. All case information letters, and the pertussis information sheet can be accessed here.

In particular, it is important that the case understands:

• which individuals are at high risk of severe disease and to avoid contact with infants, and women in their last trimester of pregnancy until they are no longer infectious
• that protection from immunisation or infection is not lifelong and the importance of timely immunisation as per the National Immunisation Schedule and that immunisation in every pregnancy is recommended. 

Where the case is a healthcare worker in a setting where there is an occupational health team, they should inform occupational health.

It is critical that a manaaki-centred, and driven, approach underpins all response and engagement mechanisms. Through best practice and culturally appropriate manaaki/wellbeing approaches that respond to the needs of Māori and Pacific people relationships and trust can be established and strengthened between public health services, cases and wider contacts.

As pertussis can be severe and usually requires a period of isolation, it can be a distressing time for whānau. The following approaches should be prioritised when engaging with cases and caregivers:

• Ensuring Māori and Pacific equity leadership to support decision making.
• Understanding and elevating the fundamental needs and priorities of whānau will help with finding the most effective and appropriate approach to engage and follow up with the case and/or their caregivers.
• Allow plenty of time to connect and communicate with the case and/or their caregivers, and to understand which of their close contacts may need to be followed up.
• Although pertussis is a vaccine-preventable disease, there are many reasons that someone may not have been immunised (including barriers to care). Consider using this opportunity to explore the reasons that cases may not have been vaccinated and address any barriers or concerns.

If the case is pregnant, it is recommended to link with their lead maternity carer to provide additional support.

A close contact can be defined as someone who has been in close proximity (within 2 metres) of the index case for one hour or more, during the case’s infectious period (including household contacts or those who have stayed overnight in the same room).

Due to their risk of severe disease, infants aged under 6 months who are exposed to an infectious case for less than one hour may warrant being considered a close contact.

The primary goal of public health action with pertussis is to protect people at risk of severe disease, especially infants who have received fewer than 3 doses of a pertussis-containing vaccine. Intensive public health follow up is not required for all contacts, but care should be taken to ensure high priority close contacts (see Table 3) are followed up for consideration of prophylactic antibiotics. For these groups, public health action should be initiated as soon as possible, and ideally within one day of notification.

High priority contacts for public health action may be identified and managed in primary care (at the time the case is identified) or in public health services (when the case is notified).

When this has not already occurred in primary care, on notification of a probable or confirmed case of pertussis, people meeting the close contact definition should be identified and contacted for provision of health information, where possible, and the provision of chemoprophylaxis, where appropriate.

Classification of close contacts should consider the factors which impact the likelihood of the close contact developing severe disease, and the risk factors for the close contact spreading pertussis to those at risk of developing severe disease.

Close contacts should be provided the information sheet for guidance on seeking medical attention if symptoms develop.

Factors which impact the likelihood of the close contact developing severe disease:

• Age.
• Immunisation status¹ (including antenatal immunisation status if pregnant or infant aged under 6 months).
• Ethnicity.
• Living with a chronic respiratory and/or immunocompromising condition.

¹ Note: Pertussis-containing vaccines take approximately 2 weeks to confer protection from time of vaccination

Risk factors for the close contact spreading pertussis to those at risk of developing severe disease:

• Whether they are pregnant (and if so, whether they are in their last trimester of pregnancy).
• Whether they routinely work with children aged under 12 months, pregnant people, or others at high risk of severe pertussis outcomes.
• Whether they live with children aged under 12 months, pregnant people, or others at risk of severe outcomes from pertussis.

Laboratory investigation is not advised for close contacts unless it has a significant impact on public health management.

All close contacts (high priority or otherwise) should be advised that isolation is not necessary unless they develop symptoms, and to seek medical attention and avoid attending early childhood services, school, work or community gatherings if they become symptomatic. It is important to clearly explain that the early stage of pertussis is indistinguishable from those of minor respiratory tract infections (i.e. colds) and this is when cases are at their most infectious.

Additional restrictions may be advised by the local medical officer of health in partnership with equity leadership, particularly where there is a significant risk of transmission to individuals at high risk of severe outcomes from pertussis.

Evidence for the effectiveness of chemoprophylaxis for contacts is limited. Therefore, antibiotics are only recommended for high priority close contacts who are within 3 weeks of exposure to an infectious case. Recommended antibiotics and dosages are the same as for case treatment (see Table 4). [4,5,8,9,10] 

Table 4: Recommended dosage of antibiotic therapy for close contacts

Raising general awareness and promoting on-time and catch-up immunisation is important.

While contact tracing, advise any unimmunised or partially-immunised close contacts to complete their immunisations as per the National Immunisation Schedule, especially pregnant people and infants aged under 12 months.

Immunisations on the National Immunisation Schedule are funded, including antenatal immunisation (recommended from 16 weeks’ gestation in every pregnancy). There are also groups for whom vaccination is recommended but not necessarily funded, including healthcare workers (every 5-10 years depending on their role).

Further information about pertussis immunisation can be found in the Immunisation Handbook including information on the National Immunisation Schedule, antenatal, and recommendations for healthcare workers).

The following information should be conveyed to close contacts verbally, and in writing via a contact information letter and the pertussis information sheet (accessible here):

• They should self-monitor for symptoms, and seek medical advice and avoid high-risk contacts/settings if they do develop symptoms.
• They are not required to isolate unless they develop early symptoms (including a mild fever, runny nose, and non-specific cough).
• If they are not fully immunised according to the National Immunisation Schedule, they should consider becoming immunised.

The letter and information sheet include information about:

• pertussis - what is it, transmission, symptoms
• what to do if symptoms occur
• chemoprophylaxis (if prescribed)
• any restriction advice (if symptoms develop)
• advice on minimising spread to others
• contact details for healthcare and public health services.

It is critical that a manaaki-centred, and driven, approach underpins all response and engagement mechanisms. Through best practice and culturally appropriate manaaki/wellbeing approaches that respond to Māori and Pacific needs, relationships and trust can be established and strengthened between public health services and close contacts.

As pertussis can be severe and usually requires a period of isolation, it can be a distressing time for whānau. The following approaches should be prioritised when engaging with close contacts and caregivers:

• Ensuring Māori and Pacific equity leadership to support decision making.
• Understanding the needs and priorities of whānau will help with finding the most effective approach to follow up.
• Although pertussis is a vaccine-preventable disease, there are many reasons that a close contact may not have been immunised (including barriers to care). Consider using this opportunity to explore the reasons that close contacts may not have been vaccinated and address any barriers or concerns.

Not applicable.

Clean and disinfect surfaces and materials contaminated by respiratory secretions.

Encourage immunisation of pregnant women from 16 weeks’ gestation at every pregnancy.

Encourage on-time immunisation, particularly for infants at 6 weeks, 3 months and 5 months.

Encourage timely immunisation of older children against pertussis at aged 4 and 11 years as per the Immunisation Handbook [8]

Encourage (re-)vaccination of immunosuppressed patients with pertussis-containing vaccine according to the existing guidance[9] (funded).

Encourage close family contacts of young infants, such as grandparents, fathers and partners to have a booster dose of pertussis vaccine to reduce spread of the disease. Older siblings should be up-to-date with their immunisations.

Encourage a booster dose against pertussis every 10 years to all lead maternity carers and other health care personnel who work in neonatal units and other clinical settings (such as GPs, practice nurses and Well Child providers), where they are exposed to infants.

Encourage a booster dose against pertussis every 10 years to all those living or working with people with a pre-existing health condition that may be exacerbated by a pertussis infection, especially health care workers.

Encourage a booster dose against pertussis every 10 years to all early childhood workers.

Promote behaviours that protect infants, such as encouraging people with a cough to keep their distance from babies.

Promote behaviours that prevent the transmission of communicable respiratory diseases.

Ensure complete case information is entered into EpiSurv.

If a cluster of cases occurs, contact 0800GETMOH - CD option, and outbreak liaison staff at ESR, and complete the Outbreak Report Form.

1. Evaluation of real-time PCR for diagnosis of Bordetella pertussis infection. Available from https://link.springer.com/article/10.1186/1471-2334-6-62 
2. Impact of polymerase chain reaction on clinical pertussis research: Finnish and Swiss experiences. Available from https://pubmed.ncbi.nlm.nih.gov/8940220/ 
3. Clinical evaluation and validation of laboratory methods for the diagnosis of Bordetella pertussis infection: Culture, polymerase chain reaction (PCR) and anti-pertussis toxin IgG serology (IgG-PT). Available from https://pubmed.ncbi.nlm.nih.gov/29652945/ 
4. Pertussis, Centers for Disease Control and Prevention website. Available from https://www.cdc.gov/pertussis/index.html 
5. Pertussis Clinical Guidelines, Starship. Available from https://starship.org.nz/guidelines/pertussis/ 
6. Committee of Infectious disease, Redbook. Available from https://publications.aap.org/redbook/book/755/Red-Book-2024-2027-Report-of-the-Committee-on?autologincheck=redirected 
7. Antibiotics for whooping cough (pertussis). Available from https://pubmed.ncbi.nlm.nih.gov/17636756/ 
8. A randomized, placebo-controlled trial of erythromycin estolate chemoprophylaxis for household contacts of children with culture-positive bordetella pertussis infection. Available from https://pubmed.ncbi.nlm.nih.gov/10506267/ 
9. Review of the evidence for the use of erythromycin in the management of persons exposed to pertussis. Available from https://pubmed.ncbi.nlm.nih.gov/9593483/ 
10. Use of antibiotics in the prevention and treatment of pertussis. Available from https://pubmed.ncbi.nlm.nih.gov/15876929/ 

• Altunaiji SM, Kukuruzovic RH, Curtis NC, Massie J. 2011. Antibiotics for whooping cough (pertussis) (Review). Cochrane Library.
• Health New Zealand | Te Whatu Ora. 2024. Immunisation Handbook 2024 Wellington:.
• CDC. Pertussis Home webpages. Postexposure Antimicrobial Prophylaxis. Information for Health professionals. Updated: August 7, 2017.
• CDC. 2005. Recommended antimicrobial agents for treatment and postexposure prophylaxis of pertussis. 2005 CDC Guidelines. Morbidity and Mortality Weekly Report. Recommendations and Reports 54(RR-14).
• CDC. 2013. Updated Recommendations for Use of Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccine (Tdap) in Pregnant Women — Advisory Committee on Immunization Practices (ACIP), 2012. Morbidity and Mortality Weekly Report. Vol. 62, No. 7, 22 February.
• Department of Health and Ageing, Australia. 2015. Pertussis National Guidelines for Public Health Units. Version 3.0. April.
• Dodhia H, Crowcroft N, Bramley JC, et al. 2002. UK Guidelines for the use of erythromycin chemoprophylaxis in persons exposed to pertussis. Journal of Public Health Medicine 24: 200–06.
• Health Protection Agency, UK. 2011. HPA Guidelines for the Public Health Management of Pertussis. February.
• Ministry of Health. 2009. National Immunisation Register.
• Ministry of Health, NSW. 2009. Pertussis Response Protocol for NSW Public Health Units. New South Wales: NSW Government.
• Public Health England, UK. 2016. Guidelines for the Public Health Management of Pertussis in England. London: Public Health England

[1]    A ‘significant increase’ is generally taken as a fourfold rise in titre, however interpretation of serology results should be discussed with the testing laboratory or ESR.

[2]   A epidemiological link is established when there is: contact between two people at a time when one of them is likely to be infectious (from the catarrhal stage, approximately 1 week before, to 3 weeks after onset of cough) AND the other has an illness which starts within 5 to 21 days after this contact AND at least one case in the chain of epidemiologically linked cases (which may involve many cases) is a confirmed case with either laboratory definitive or laboratory suggestive evidence.

[3]    Although Public Health England guidelines (updated 9 December 2016) recommend an exclusion of 2 days for all excluded cases, the clearance of B. pertussis with other antibiotics may not be as rapid.

[4]    See the New Zealand Formulary for Children and New Zealand Formulary for Adults.

[5]   The Immunisation Handbook 2017 currently recommends boosters (funded) for pregnant women between 28–38 weeks gestation in each pregnancy and boosters (not funded) at 10–yearly intervals for certain groups (pp. 383–385). Recommended timing will be kept under review, given that immunity wanes after 5–10 years from the last pertussis vaccine dose (MMWR Vol. 54 No. RR-14 December 9, 2005).

[6]   Susceptible contacts are defined as those who are not fully immunised for their age, or if they are over 16 years of age and have not received a booster of pertussis-containing vaccine in the last 5 years.

[7]  Pertussis vaccine should be offered in every pregnancy (currently funded for pregnant women between 28-38 weeks gestation). Vaccination of pregnant women is likely to result in increased immunity in the newborn infant, as well as in the mother (also see Updated Recommendations for Use of Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccine (Tdap) in Pregnant Women — Advisory Committee on Immunization Practices (ACIP), 2012. MMWR. Vol. 62, No. 7, 22 February 2013).

[8]    Refer to section 16.5.1.1 'Children' of the Immunisation Handbook.

[9]    Refer to section 16.5.3. ‘(Re)vaccination’ of the Immunisation Handbook.