key: cord-0782184-crbl1wfa
authors: Keehner, Jocelyn; Horton, Lucy E.; Pfeffer, Michael A.; Longhurst, Christopher A.; Schooley, Robert T.; Currier, Judith S.; Abeles, Shira R.; Torriani, Francesca J.
title: SARS-CoV-2 Infection after Vaccination in Health Care Workers in California
date: 2021-03-23
journal: N Engl J Med
DOI: 10.1056/nejmc2101927
sha: f29e12244fb7ee7a88731f9ff1d7aad8cb67fa42
doc_id: 782184
cord_uid: crbl1wfa

nan

after vaccination, and the majority (71%) of these persons tested positive within the first 2 weeks after the first dose. After receiving both vaccinations, 37 health care workers tested positive; of these workers, 22 had positive test results 1 to 7 days after the second dose. Only 8 health care workers tested positive 8 to 14 days after the second vaccination, and 7 tested positive 15 or more days after the second vaccination ( Table 1) . As of February 9, a total of 5455 health care workers at UCSD and 9535 at UCLA had received the second dose 2 or more weeks previously; these findings correspond to a positivity rate of 0.05%.

In our cohort, the absolute risk of testing positive for SARS-CoV-2 after vaccination was 1.19% among health care workers at UCSD and 0.97% among those at UCLA; these rates are higher than the risks reported in the trials of mRNA-1273 vaccine 1 and BNT162b2 vaccine. 2 Possible explanations for this elevated risk include the availability of regular testing for asymptomatic and symptomatic persons at our institutions, a regional surge in infections in Southern California during our vaccination campaigns, 5 and differences in demographic characteristics between the trial participants and the health care workers in our cohort. The health care workers were younger and had an overall higher risk of exposure to SARS-CoV-2 than the participants in the clinical trials. In addition, the cutoff dates for reporting in both initial vaccine trials were well before this surge, no testing of asymptomatic persons was included in the BNT162b2 vaccine trial, 2 and only a single screening of asymptomatic persons was performed in the mRNA-1273 vaccine trial before the second dose was administered. 1 The rarity of positive test results 14 days after administration of the second dose of vaccine is encouraging and suggests that the efficacy of these vaccines is maintained outside the trial setting. These data underscore the critical importance of continued public health mitigation measures (masking, physical distancing, daily symptom screening, and regular testing), even in environments with a high incidence of vaccination, until herd immunity is reached at large. 

Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine

Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine

BNT162b2 mRNA Covid-19 vaccine in a nationwide mass vaccination setting

Rapid response to COVID-19: health informatics support for outbreak management in an academic health system

An interactive web-based dashboard to track COVID-19 in real time

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