Q fever

What

Q fever is caused by the bacterium Coxiella burnetii. C. burnetii infects wild and domestic animals, and their ticks. Humans are mainly infected from cattle, sheep and goats.

Who

Q fever vaccine is recommended for adolescents aged ≥15 years and adults who are at risk of infection with C. burnetii. These include:

• abattoir workers
• farmers
• stockyard workers
• shearers
• animal transporters (of high-risk animals such as cattle, camels, sheep, goats and kangaroos)
• veterinarians, veterinary nurses and veterinary students
• professional dog and cat breeders
• pet food manufacturing workers
• agricultural college staff and students
• wildlife and zoo workers who work with high-risk animals, including kangaroos and bandicoots
• animal refuge workers (including those working in animal shelters and boarding facilities)
• people who cull or process kangaroos or camels
• laboratory workers who handle veterinary specimens or work with C. burnetii
• other people exposed to high-risk animals

People should have both serological and skin tests before vaccination.

How

Q fever vaccine is given as a single dose. Booster doses are not recommended.

People should receive serum antibody testing and a skin test before vaccination (together known as pre-vaccination testing).

Pre-vaccination testing is not needed in people who have a documented history of previous infection with Q fever or have already received a Q fever vaccine. Q fever vaccine is contraindicated in these people.

Why

Acute Q fever symptoms are influenza-like. However, some cases develop hepatitis and pneumonia. Complications of Q fever are endocarditis and post–Q fever fatigue syndrome.

Q fever vaccines available in Australia

The Therapeutic Goods Administration website provides product information for each vaccine.

See also Vaccine information and Variations from product information for more details.

Dose and route

The dose of Q fever vaccine is 0.5 mL given by subcutaneous injection.

It is important to complete pre-vaccination testing before vaccinating. Both serological and skin tests must be negative before vaccination. See Pre-vaccination testing in Recommendations.

The manufacturer (Seqirus) and the Australian College of Rural and Remote Medicine both provide online education on Q fever vaccination and skin testing.

Contraindications

Q fever vaccine is contraindicated in people who:

• have had anaphylaxis after a component of Q fever vaccine
• have had anaphylaxis to eggs
• have a history of laboratory-confirmed Q fever
• have other medical documentation that supports a previous diagnosis of Q fever
• have positive or equivocal antibody to Q fever by serological testing
• are sensitive to the organism by skin testing
• have been vaccinated against Q fever
• are immunocompromised (no information is available on the accuracy of skin testing or the efficacy and safety of Q fever vaccine in people who are immunocompromised)

Precautions

All people who are being considered for vaccination with Q fever vaccine must have serum antibody testing and skin testing before vaccination. See Pre-vaccination testing in Recommendations.

Egg allergy

People with a known allergy to eggs who want receive Q fever vaccine should discuss this with an immunologist or allergist, or be referred to a specialised immunisation adverse events clinic.

Women who are pregnant or breastfeeding

Q fever vaccine is not routinely recommended for pregnant or breastfeeding women. 

Q fever vaccine contains inactivated products. Inactivated bacterial vaccines are not harmful in pregnancy. However, the vaccine’s safety in pregnancy has not been established. 

No information is available on breastfeeding women receiving Q fever vaccine.

See Table. Vaccines that are not routinely recommended in pregnancy: inactivated bacterial vaccines in Vaccination for women who are planning pregnancy, pregnant or breastfeeding for more details.

Common adverse events

Q fever vaccine is reported to be reactogenic among respondents; however, adverse events following immunisation are usually minor.² Common adverse events are tenderness (48-95% of vaccine recipients) and erythema (33-58%) at the injection site. Induration or oedema at the injection site is uncommon and occurs in <1% of recipients.^1-3

Other adverse events reported include:²

• any systemic features (59.5%)
• headache (43.9%)
• fever (17.2%)
• lethargy (42.7%)
• joint pain (24.6%)

Rare adverse events

People who have previously been exposed to Q fever may have a severe injection site reaction shortly after vaccination. In some cases, an abscess then develops, which requires excision and drainage. The person may also have short-term systemic symptoms that resemble post–Q fever fatigue syndrome in Clinical features.

Not all people with positive pre-vaccination tests develop severe reactions.

Pre-vaccination testing means that immune people are rarely vaccinated, and these reactions are very rare.

Early clinical trials reported serious adverse reactions.⁴ However, these involved the use of vaccines with varying composition, given repeatedly and without any pre-vaccination testing.⁴

Lesions at the injection site have also been reported in people who:

• are negative for the skin and antibody tests before vaccination
• do not have any immediate reaction

Some people develop an indurated lesion at the injection site about 1–8 months after vaccination.

When the indurated lesion develops, the original skin test site often becomes positive. This suggests a late-developing cellular immune response.

The lesions are not fluctuant and do not progress to an abscess. Most lesions gradually decrease in size and resolve over several months without treatment.^5,6

Q fever is caused by Coxiella burnetii, an obligate intracellular bacterium.⁷  C. burnetii infects wild and domestic animals, and their ticks. Humans are mainly infected from cattle, sheep and goats.^8-10 Other animals that may be infected are:^8,10-12

• companion animals such as cats and dogs
• native Australian animals such as kangaroos
• introduced animals such as feral cats and camels

Pathogenesis

Acute Q fever usually has an incubation period of 2–3.5 weeks, depending on the inoculum size and other variables.¹³ The incubation period ranges from 4 days to 6 weeks.

Pasteurisation temperatures inactivate the organism.

Transmission

Animals shed C. burnetii into the environment through their: 

• placental tissue or birth fluids, which contain very high numbers of bacteria
• milk
• urine
• faeces

C. burnetii is highly infectious,¹⁴ and can survive in air, soil, water and dust.^15,16

Humans can inhale infected aerosols or dust and become infected. The organism may spread on fomites such as:^15,16

• wool
• hides
• clothing
• straw
• packing materials

C. burnetii has been weaponised and is a category B biothreat agent.¹⁷

Q fever can be an acute or a chronic disease. It can have long-term sequelae. However, infection is asymptomatic in at least half of cases.^1,18

Acute Q fever

Clinical symptoms include rapid onset of:^1,18,19

• high fever
• rigors
• profuse sweats
• extreme fatigue
• muscle and joint pain
• severe headache
• photophobia

As the disease progresses, people can develop hepatitis, sometimes with jaundice. Some people develop pneumonia. This is usually mild but may be severe, requiring mechanical ventilation.

If untreated, the acute illness usually lasts 1–3 weeks. In severe cases, people may have substantial weight loss.^1,18 Time off work can last a few days to several weeks.²⁰

Chronic Q fever

Coxiella burnetii may cause chronic disease. The most common complication in adults is subacute endocarditis.¹⁹ Less common disease manifestations are caused by granulomatous lesions in:

• bone (that is, osteomyelitis)
• joints
• liver
• lung
• testis 
• other sites such as soft tissues

Infection in pregnancy can result in fetal death, intrauterine growth restriction and premature delivery.²¹

Post–Q fever fatigue syndrome

About 10–15% of people who have had acute Q fever develop post–Q fever fatigue syndrome.^22-25 Research suggests that non-infective antigenic complexes of C. burnetii persist for many years after acute Q fever. The immune system may continue to respond to these antigens, which might be the biological basis of the syndrome.^23,26-28

People most at risk of Q fever

People most at risk include workers in the meat and livestock industries (including shearers). New employees or visitors to these settings have the highest risk of infection.

However, Q fever is not confined to occupationally exposed groups. Sporadic cases or outbreaks occur in the general population if people are exposed to infected animals in settings such as:

• stockyards
• feedlots
• processing plants 
• farms 

Most notifications occur among men from rural areas or with occupational exposure. However, a serosurvey from Queensland indicated a high rate of exposure among urban residents, including women and children.²⁹

Q fever in Australia

Nationally, Q fever is an uncommon disease. However, some population groups have much higher incidence of disease (see People most at risk of Q fever).

Q fever vaccine has been used in abattoir workers since the early 1990s. Between 2001 and 2006, the Australian Government sponsored the National Q Fever Management Program.³⁰ The program funded screening and vaccination for abattoir workers, shearers, farmers, and their families and employees in the livestock-rearing industries.

After the program started, the number of Q fever cases reported to the National Notifiable Diseases Surveillance System declined by more than 50%.³⁰ The greatest reductions were among young men aged 15–39 years. This is consistent with documented high vaccine uptake among abattoir workers.^30-32

Although the overall national Q fever notification rate is low at about 2 cases per 100,000 population, there are geographical ‘hot spots’ for Q fever in central Queensland and around the New South Wales – Queensland border, where the notification rate exceeds 13 cases per 100,000 population.³³

In 2014, Q fever notifications were most common in adult males. However, there were also notified cases in children aged <15 years.³³ Q fever cases have also been reported in:^20,34

• other occupational groups^35,36
• cases with non-occupational animal exposure³⁷

Q-Vax and Q-Vax Skin Test contain a purified killed suspension of Coxiella burnetii. The vaccine is prepared from bacteria that have been cultivated in embryonated hens’ eggs.

Seroconversion after vaccination

A vaccine trial among abattoir workers showed that 80–82% seroconverted after vaccination. 85–95% of vaccinated people developed cell-mediated immunity that lasted for at least 5 years.³⁸

Vaccine efficacy

Vaccine efficacy is estimated to be 83–100%, based on the results of open and placebo-controlled trials, and post-marketing studies.^38-42

Transport according to National vaccine storage guidelines: Strive for 5.⁴³ Store at +2°C to +8°C. Do not freeze or store in direct contact with ice packs. Do not use the vaccine if it has been exposed to temperatures less than 0°C. Protect from light.

Freshly prepare diluted Q-Vax Skin Test. Store at +2°C to +8°C and use within 6 hours.

Q fever is a notifiable disease in all states and territories in Australia.

State or territory public health authorities can provide advice about the public health management of Q fever.

The product information for Q-Vax does not include the use of a reduced vaccine dose in people who have indeterminate results from serological or skin testing.

The Australian Technical Advisory Group on Immunisation (ATAGI) recommends that experienced Q fever vaccination providers can give sequential reduced (split volume) vaccine doses to people with indeterminate results from pre-vaccination screening.

The product information for Q-Vax states that this vaccine is for vaccination of adults.

ATAGI recommends that Q-Vax can be used in people aged ≥15 years.

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3. Seqirus. Product information: Q-VAX® Q fever vaccine and Q-VAX® Skin test (AUST R 100517 & 100518). 2016. 
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