Table 4. Vaccine effectiveness against breakthrough SARS-CoV-2 infection of any severity, 2 or 3 doses versus unvaccinated, Western Australia, Australia, February 1, 2022–May 31, 2022*.

Case-patients			Controls		Vaccine effectiveness, % (95% CI)†
Vaccinated	Unvaccinated		Vaccinated	Unvaccinated
16,306	6,060		17,292	5,074	24.9 (21.2–28.4)
103,741	14,299		108,863	9,177	42.0 (40.2–43.6)

*Case-patient (SARS-CoV-2 positive) and control (SARS-CoV-2 negative) pairs (infection status determined by PCR) matched by age group, sex, Aboriginality, testing week, Index of Relative Socioeconomic Advantage and Disadvantage decile and comorbidities. †Vaccine effectiveness = 1 − adjusted odds ratio (ascertained by using conditional logistic regression of matched pairs).