Table 4.

Risk Ratios for Infection With Presumptive B.1.427/B.1.429 Among Healthcare Personnel by Vaccination Status and Adjusted for Community Prevalence of L452R Mutation at Time of Infection

Vaccination Status at Time of Positive Test	n	Presumptive B.1.427/B.1.429, n (%)	Concomitant Community Prevalence of L452R Median (Quartiles)	Unadjusted RR (95% CI)	Adjusted RR (95% CI)
Unvaccinated	130	61 (46.9)	41.4% (32.8%, 47.4%)	Ref.	Ref.
Early post-vaccination	74	22 (29.7)	36.2% (32.8%, 41.4%)	0.63 (.43–.94)	0.70 (.47–1.05)
Partially vaccinated	21	10 (47.6)	41.4% (32.8%, 45.7%)	1.02 (.63–1.65)	1.05 (.65–1.70)
Fully vaccinated	17	10 (58.8)	51.8% (50.7%, 57.7%)	1.25 (.81–1.94)	1.05 (.65–1.68)

Modified Poisson regression model (log-Poisson generalized linear model with robust standard errors) comparing individuals with and without presumptive B.1.427/B.1.429 by vaccination status at time of positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid amplification test (NAAT) and adjusted for percent of total positive SARS-CoV-2 tests with isolated L452R mutation presumptive of B.1.427/B.1.429 within Stanford Health Care during week of infection. Early post-vaccination = positive SARS-CoV-2 NAAT <14 days from vaccine dose 1, partially vaccinated = positive SARS-CoV-2 NAAT >14 days from vaccine dose 1 and <14 days from vaccine dose 2, fully vaccinated = positive SARS-CoV-2 NAAT >14 days from vaccine dose 2.

Abbreviations: CI, confidence interval; RR, risk ratio.