People are recommended to have both serological and skin tests before Q fever vaccination
People who are being considered for Q fever vaccination must have both serum antibody testing and a skin test before Q fever vaccination. The tests can be done on the same day. This is to identify people who have been previously infected with the Q fever organism and are not aware of it. These people are likely to have adverse reactions to the vaccine, based on hypersensitivity to the organism. People who have been previously infected with the Q fever organism should not be vaccinated.
It is also important to obtain a detailed history from all people who want a Q fever vaccine. People who have possibly been infected should provide (if available) either:
- documentation of previous Q fever vaccination, or
- laboratory test results confirming previous Q fever infection
In particular, people who have worked in the livestock or meat industries for a long time should be carefully questioned about their medical and vaccination histories. The Australian Q Fever Register has records of some people who have received Q fever vaccine. Registered users can access the register.
Pre-vaccination testing is not needed for people who have:
- a documented history of previous infection with Q fever
- already received a Q fever vaccine
The vaccine is contraindicated in these people.
Some people who have had confirmed Q fever infection in the past may show no response to serological or skin testing. However, they may still have serious reactions to Q fever vaccine. See Contraindications and precautions.
Conducting pre-vaccination testing
Only experienced people should conduct skin testing and interpretation. The Australian Q Fever Register has details of immunisation providers who are trained to administer Q fever skin testing.
To perform skin testing:
- dilute 0.5 mL of Q-Vax Skin Test in 14.5 mL of sodium chloride (injection grade)
- store freshly prepared diluted Q-Vax Skin Test at +2°C to +8°C, and use within 6 hours
- if the skin is not visibly clean, use methylated spirits to clean the area — do not use commercial isopropyl alcohol skin wipes
- inject a 0.1 mL dose of the diluted Q-Vax Skin Test intradermally into the volar surface of the forearm
Read the skin test after 7 days. Skin reactions are common 3–4 days after skin testing, but these generally resolve by day 7. A positive reaction is indicated by any induration at the injection site after 7 days.
Serological and skin test results should be taken into account according to Table. Interpreting serological and skin test results before Q fever vaccination.
Interpreting pre-vaccination test results
Use serology and skin test results to determine whether a person should be vaccinated.
See Table. Interpreting serological and skin test results before Q fever vaccination shows the results and interpretation for pre-vaccination tests.
| Serology | Skin test | Interpretation and action |
|---|---|---|
|
Positive antibody test (according to diagnostic laboratory criteria):
|
Any skin test result | Sensitised: do not vaccinate |
|
Equivocal antibody test (according to diagnostic laboratory criteria):
|
Positive (induration) | Sensitised: do not vaccinate |
| Borderline (induration just palpable) or negative (no induration) | Indeterminate (see Managing people with indeterminate test results) | |
|
Negative antibody test (according to diagnostic laboratory criteria):
|
Positive | Sensitised: do not vaccinate |
| Borderline | Indeterminate (see Managing people with indeterminate test results) | |
| Negative | Non-immune: vaccinate | |
| Source: Modified from Marmion1 | ||
Managing people with indeterminate test results
Managing people with indeterminate test results
Test results are ‘indeterminate’ when:
- the skin test induration is just palpable and the antibody test is either equivocal or negative
- there is no skin induration and an equivocal antibody test
A small proportion of people may have an indeterminate result. This may be because of past infection with Coxiella burnetii. It may also indicate that the person has antibodies to antigens that C. burnetii shares with other bacteria.
Manage this finding by either repeating the tests or vaccinating over 2 occasions.
Repeating pre-vaccination tests
Repeating pre-vaccination tests
Repeat the skin and serological tests around 2–3 weeks after first testing. Interpret the tests as for initial testing in Table. Interpreting serological and skin test results before Q fever vaccination.
Serum is collected to look for a rise in the titre of C. burnetii antibodies. A rise in titre between paired sera may indicate recent Q fever infection, and the person should be managed accordingly.
Vaccinating with a divided dose over 2 occasions
Vaccinating with a divided dose over 2 occasions
Vaccinate with a subcutaneous injection of a 5 µg (0.1 mL) dose instead of 25 µg (0.5 mL).
Check for adverse events 48 hours after the injection, such as severe local induration, severe systemic effects or fever.
If there are no adverse events, give a further 0.4 mL (20 µg) dose of the vaccine within the next 2–3 weeks. This is before cell-mediated immunity develops to the 1st dose.