Positive Q fever skin test after vaccination

To the Editor: In May 2000 and December 2001, I vaccinated two women for Q fever (Q-Vax, CSL). Both had negative blood tests (IgG < 1:10 by immunofluoresence) and skin tests. Both had local reactions similar to those described by Mills et al.1 In both women, the skin test became positive after vaccination.

The first woman had visited a farm on weekends, but had had no direct exposure to cattle, sheep or goats. Swelling at the vaccination site occurred within 72 hours, forming a lump 70 mm x 30 mm in size and causing significant discomfort. The skin test became positive at the same time. A surgeon excised the lesion 5 months after vaccination, and scarring resulted. The histological appearance was similar to that described by Mills et al,1 including a granulomatous panniculitis. The tissue was weakly positive for Coxiella burnetii by a polymerase chain reaction test (Professor B P Marmion, Institute of Medical and Veterinary Science, Adelaide). The skin test was still positive 7 months after vaccination.

The second vaccine recipient lived on a cattle property and was involved with calving. She reported that her skin test became positive 5 weeks after vaccination (an observation confirmed by me a week later). The test was still positive at my final review 4 months after vaccination. Although the swelling at the vaccination site reached 50 mm × 20 mm, it caused little local pain or inconvenience. The lesion resolved spontaneously without scarring.

The first of these cases had a much shorter onset period than that described by Mills et al.1 Their article did not document the fate of the skin tests, but based on the two cases I report here, and other cases notified to me by general practitioners, I suspect that prolonged positivity may be the rule rather than the exception.