Editor's Note: This letter of the alphabet was published on March 23, 2021, at NEJM.org.

Correspondence

SARS-CoV-2 Infection after Vaccination in Health Intendance Workers in California

To the Editor:

Data from stage 3 clinical trials of messenger RNA (mRNA) vaccines through November 2020 showed 94.1% efficacy for the prevention of symptomatic severe acute respiratory syndrome coronavirus ii (SARS-CoV-ii) infection at 14 days after the second dose of the mRNA-1273 vaccine (Moderna)1 and 95% efficacy at vii days afterward the 2nd dose of the BNT162b2 vaccine (Pfizer).2 Since the results of these trials were published, a nationwide surge in coronavirus disease 2019 (Covid-xix) has been noted, SARS-CoV-2 variants with increased infectivity have emerged, the Food and Drug Assistants has granted emergency use authority for these ii mRNA vaccines, and vaccination has been initiated across the The states.

Since the showtime of the vaccination campaign, the development of Covid-19 has been reported in persons who have received ane or both doses of vaccine.three Both the Academy of California, San Diego (UCSD) and the University of California, Los Angeles (UCLA) health systems began to vaccinate wellness care workers on December 16, 2020. On December two, in addition to defining a low threshold for testing of symptomatic persons, UCSD mandated that asymptomatic health intendance workers undergo weekly testing by polymerase-concatenation-reaction (PCR) analysis of nasal swabs. On December 26, UCLA instituted an optional testing programme for asymptomatic health care workers with PCR assay of nasal swabs. This program has allowed for increased detection of asymptomatic SARS-CoV-ii infections after vaccination.

Pooled data were obtained in deidentified format from an electronic employee wellness tape system at UCSD and UCLA.4 Exemption from institutional review board blessing was obtained.

New SARS-CoV-2 Infections amidst Vaccinated Wellness Care Workers from December xvi, 2020, through February 9, 2021.

From December 16, 2020, through February 9, 2021, a total of 36,659 health care workers received the beginning dose of vaccine, and 28,184 of these persons (77%) received the second dose. Among the vaccinated wellness care workers, 379 unique persons tested positive for SARS-CoV-ii at least ane twenty-four hours subsequently vaccination, and the majority (71%) of these persons tested positive inside the kickoff 2 weeks later on the first dose. After receiving both vaccinations, 37 wellness care workers tested positive; of these workers, 22 had positive test results 1 to 7 days later on the second dose. Only 8 wellness care workers tested positive 8 to fourteen days after the second vaccination, and 7 tested positive 15 or more than days after the second vaccination (Table 1). Every bit of February 9, a full of 5455 health care workers at UCSD and 9535 at UCLA had received the second dose ii or more weeks previously; these findings represent to a positivity rate of 0.05%.

In our cohort, the absolute hazard of testing positive for SARS-CoV-2 afterward vaccination was 1.19% among health intendance workers at UCSD and 0.97% amongst those at UCLA; these rates are college than the risks reported in the trials of mRNA-1273 vaccineone and BNT162b2 vaccine.ii Possible explanations for this elevated gamble 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 add-on, 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,ii 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 later administration of the 2d 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 loftier incidence of vaccination, until herd immunity is reached at big.

Jocelyn Keehner, G.D.
Lucy E. Horton, Thousand.D., M.P.H.
UC San Diego Wellness, San Diego, CA

Michael A. Pfeffer, K.D.
David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA

Christopher A. Longhurst, M.D.
Robert T. Schooley, Grand.D.
UC San Diego Health, San Diego, CA

Judith S. Currier, K.D.
David Geffen Schoolhouse of Medicine at UCLA, Los Angeles, CA

Shira R. Abeles, M.D.
Francesca J. Torriani, M.D.
UC San Diego Health, San Diego, CA
[e-mail protected]

Disclosure forms provided by the authors are available with the full text of this letter at NEJM.org.

This letter was published on March 23, 2021, at NEJM.org.

Drs. Abeles and Torriani contributed as to this letter.

  1. i. Baden LR, El Sahly HM, Essink B, et al. Efficacy and safety of the mRNA-1273 SARS-CoV-two vaccine. Northward Engl J Med 2021;384:403-416.

  2. 2. Polack FP, Thomas SJ, Kitchin Due north, et al. Prophylactic and efficacy of the BNT162b2 mRNA Covid-19 vaccine. North Engl J Med 2020;383:2603-2615.

  3. 3. Dagan N, Barda N, Kepten E, et al. BNT162b2 mRNA Covid-19 vaccine in a nationwide mass vaccination setting. N Engl J Med 2021;384:1412-1423.

  4. four. Reeves JJ, Hollandsworth HM, Torriani FJ, et al. Rapid response to COVID-19: health information science back up for outbreak management in an academic wellness organization. J Am Med Inform Assoc 2020;27(half dozen):853-859.

  5. five. Dong E, Du H, Gardner 50. An interactive web-based dashboard to runway COVID-19 in real time. Lancet Infect Dis 2020;20:533-534.

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