Editor's Note: This alphabetic character was published on March 23, 2021, at NEJM.org.

Correspondence

SARS-CoV-ii Infection after Vaccination in Health Care Workers in California

To the Editor:

Data from phase iii clinical trials of messenger RNA (mRNA) vaccines through November 2020 showed 94.ane% efficacy for the prevention of symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-two) infection at 14 days after the second dose of the mRNA-1273 vaccine (Moderna)i and 95% efficacy at 7 days after the 2nd dose of the BNT162b2 vaccine (Pfizer).2 Since the results of these trials were published, a nationwide surge in coronavirus illness 2019 (Covid-19) has been noted, SARS-CoV-2 variants with increased infectivity have emerged, the Food and Drug Administration has granted emergency utilise authorization for these two mRNA vaccines, and vaccination has been initiated beyond the U.s.a..

Since the start of the vaccination entrada, the development of Covid-nineteen has been reported in persons who have received ane or both doses of vaccine.3 Both the University of California, San Diego (UCSD) and the University of California, Los Angeles (UCLA) wellness systems began to vaccinate health care workers on December 16, 2020. On December ii, in addition to defining a low threshold for testing of symptomatic persons, UCSD mandated that asymptomatic health care workers undergo weekly testing past polymerase-concatenation-reaction (PCR) analysis of nasal swabs. On December 26, UCLA instituted an optional testing program for asymptomatic health care workers with PCR assay of nasal swabs. This program has allowed for increased detection of asymptomatic SARS-CoV-2 infections subsequently vaccination.

Pooled information were obtained in deidentified format from an electronic employee health record system at UCSD and UCLA.four Exemption from institutional review board approving was obtained.

New SARS-CoV-2 Infections amongst Vaccinated Health Care Workers from December 16, 2020, through February nine, 2021.

From December 16, 2020, through February nine, 2021, a total of 36,659 wellness intendance workers received the first dose of vaccine, and 28,184 of these persons (77%) received the second dose. Among the vaccinated health care workers, 379 unique persons tested positive for SARS-CoV-2 at least one solar day afterwards vaccination, and the majority (71%) of these persons tested positive within the first 2 weeks later on the first dose. After receiving both vaccinations, 37 health care workers tested positive; of these workers, 22 had positive examination 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 seven tested positive 15 or more than days afterward the 2d vaccination (Table 1). As of February ix, a total of 5455 health care workers at UCSD and 9535 at UCLA had received the second dose two or more weeks previously; these findings correspond to a positivity rate of 0.05%.

In our cohort, the accented risk of testing positive for SARS-CoV-ii after vaccination was i.19% among wellness care workers at UCSD and 0.97% amidst those at UCLA; these rates are higher than the risks reported in the trials of mRNA-1273 vaccinei 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 intendance workers in our accomplice. The wellness care workers were younger and had an overall higher adventure 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,2 and only a unmarried screening of asymptomatic persons was performed in the mRNA-1273 vaccine trial before the 2nd dose was administered.1

The rarity of positive test results 14 days afterward administration of the second dose of vaccine is encouraging and suggests that the efficacy of these vaccines is maintained outside the trial setting. These information 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.

Jocelyn Keehner, Thou.D.
Lucy Due east. Horton, M.D., M.P.H.
UC San Diego Health, San Diego, CA

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

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

Judith S. Currier, Grand.D.
David Geffen School of Medicine at UCLA, Los Angeles, CA

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

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

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

Drs. Abeles and Torriani contributed equally to this letter.

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

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

  3. 3. Dagan N, Barda Due north, Kepten E, et al. BNT162b2 mRNA Covid-nineteen 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-xix: wellness informatics back up for outbreak direction in an academic health organization. J Am Med Inform Assoc 2020;27(six):853-859.

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

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